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See detailImproved FTIR retrieval strategy for HCFC-22 (CHClF2), comparisons with in situ and satellite datasets with the support of models, and determination of its long-term trend above Jungfraujoch
Prignon, Maxime; Chabrillat, Simon; Minganti, Daniele; O'Doherty, Simon; Servais, Christian; Stiller, Gabriele; Toon, Geoffrey C.; Vollmer, Martin K.; Mahieu, Emmanuel

in Atmospheric Chemistry and Physics Discussions (2019)

Hydrochlorofluorocarbons (HCFC) are the first but temporary substitution products to the strong ozone depleting chloroflurocarbons (CFC). HCFC consumption and production are currently regulated under the Montreal Protocol on Substances that Deplete the Ozone Layer and their emissions have started to stabilize or even decrease. As HCFC-22 (CHClF2) is by far the most abundant HCFC in today’s atmosphere, it is crucial to continue to monitor the evolution of its atmospheric concentration. In this study, we describe an improved HCFC-22 retrieval strategy from ground-based high-resolution Fourier Transform infrared (FTIR) solar spectra recorded at the high altitude scientific station of Jungfraujoch (Swiss Alps, 3580 m above mean sea level). This new strategy distinguishes tropospheric and lower stratospheric partial columns. Comparisons with independent datasets (AGAGE and MIPAS) supported by models (BASCOE CTM and WACCM) demonstrate the validity of our tropospheric and lower stratospheric long-term time series. A trend analysis on the miscellaneous datasets used here, now spanning thirty years, confirms the last decade’s slowing down of the HCFC-22 growth rate. This updated retrieval strategy can be adapted for other ozone depleting substances (ODS) as CFC-12, for example. Measuring or retrieving ODS atmospheric concentrations is essential to scrutinise the fulfilment of the globally ratified Montreal Protocol.

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See detailAtmospheric implications of large C2-C5 alkane emissions from the U.S. oil and gas industry
Tzompa-Sosa, Z; Henderson, B H; Keller, C A; Travis, K; Mahieu, Emmanuel; Franco, B; Estes, M; Helmig, D; Fried, A; Richter, D; Weibring, P; Walega, J; Blake, D R; Hannigan, J W; Ortega, I; Conway, S; Strong, K; Fischer, E V

in Journal of Geophysical Research. Atmospheres (2019), (2013), 1--22

Emissions of C2-C5 alkanes from the U.S. oil and gas sector have changed rapidly over the last decade. We use a nested GEOS-Chem simulation driven by updated 2011NEI emissions with aircraft, surface and column observations to 1) examine spatial patterns in the emissions and observed atmospheric abundances of C2-C5 alkanes over the U.S., and 2) estimate the contribution of emissions from the U.S. oil and gas industry to these patterns. The oil and gas sector in the updated 2011NEI contributes over 80% of the total U.S. emissions of ethane (C2H6) and propane (C3H8), and emissions of these species are largest in the central U.S. Observed mixing ratios of C2-C5 alkanes show enhancements over the central U.S. below 2 km. A nested GEOS-Chem simulation underpredicts observed C3H8 mixing ratios in the boundary layer over several U.S. regions and the relative underprediction is not consistent, suggesting C3H8 emissions should receive more attention moving forward. Our decision to consider only C4-C5 alkane emissions as a single lumped species produces a geographic distribution similar to observations. Due to the increasing importance of oil and gas emissions in the U.S., we recommend continued support of existing long-term measurements of C2-C5 alkanes. We suggest additional monitoring of C2-C5 alkanes downwind of northeastern Colorado, Wyoming and western North Dakota to capture changes in these regions. The atmospheric chemistry modeling community should also evaluate whether chemical mechanisms that lump larger alkanes are sufficient to understand air quality issues in regions with large emissions of these species.

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See detailUpdate on Ozone-Depleting Substances (ODSs) and Other Gases of Interest to the Montreal Protocol
Engel, A; Rigby, M; Burkholder, J; Fernandez, R P; Froidevaux, L; Hall, B; Hossaini, R; Saito, T; Vollmer, M K; Yao, B; Liang, Q; Reimann, S; Atlas, E; Bernath, P F; Blake, D R; Dutton, G; Krummel, P; Laube, J C; Mahieu, Emmanuel; Montzka, S A; Mühle, J; Nedoluha, G; O'Doherty, S J; Oram, D E; Pfeilsticker, K; Prinn, R G; Quack, B; Simpson, I J; Weiss, R F

in Fahey, David W; Newman, Paul A; Pyle, John A; Safari, Bonfils (Eds.) Scientific Assessment of Ozone Depletion: 2018 (2019)

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See detailObserving the atmospheric evolution of ozone-depleting substances
Reimann, Stefan; Elkins, James W.; Fraser, Paul J.; Hall, Bradley D.; Kurylo, Michael J.; Mahieu, Emmanuel; Montzka, Stephen A.; Prinn, Ronald G.; Rigby, Matthew; Simmonds, Peter G.; Weiss, Ray F.

in Comptes Rendus Geoscience (2018), 350

The atmospheric observations of ozone-depleting substances (ODSs) have been essential for following their atmospheric response to the production and use restrictions imposed by the Montreal Protocol and its Amendments and Adjustments. ODSs have been used since the first half of the 20th century in industrial and domestic applications. However, their atmospheric growth went unnoticed until the early 1970s, when they were discovered using gas chromatograph-electron capture detection (GC-ECD) instruments. Similar instrumentation formed the basis of global flask and in situ measurements commenced by NOAA and ALE/GAGE/AGAGE in the late 1970s. The combination of these networks, supported by a number of other laboratories, has been essential for following the tropospheric trends of ODSs. Additionally, ground-based remote sensing measurements within NDACC and aircraft-based observation programs have been crucial for measuring the evolution of the ODS abundances over the entire atmosphere. Maintaining these networks at least at their current state is vital for ensuring the on-going verification of the success of the Montreal Protocol.

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See detailComparison of mean age of air in five reanalyses using the BASCOE transport model
Chabrillat, S.; Vigouroux, C.; Christophe, Y.; Engel, A.; Errera, Q.; Minganti, Daniele; Monge-Sanz, B. M.; Segers, A.; Mahieu, Emmanuel

in Atmospheric Chemistry and Physics (2018), 18

We present a consistent intercomparison of the mean age of air (AoA) according to five modern reanalyses: the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim), the Japanese Meteorological Agency's Japanese 55-year Reanalysis (JRA-55), the National Centers for Environmental Prediction Climate Forecast System Reanalysis (CFSR) and the National Aeronautics and Space Administration's Modern Era Retrospective analysis for Research and Applications version 1 (MERRA) and version 2 (MERRA-2). The modeling tool is a kinematic transport model driven only by the surface pressure and wind fields. It is validated for ERA-I through a comparison with the AoA computed by another transport model. The five reanalyses deliver AoA which differs in the worst case by 1 year in the tropical lower stratosphere and more than 2 years in the upper stratosphere. At all latitudes and altitudes, MERRA-2 and MERRA provide the oldest values ( ∼ 5–6 years in midstratosphere at midlatitudes), while JRA-55 and CFSR provide the youngest values ( ∼ 4 years) and ERA-I delivers intermediate results. The spread of AoA at 50hPa is as large as the spread obtained in a comparison of chemistry–climate models. The differences between tropical and midlatitude AoA are in better agreement except for MERRA-2. Compared with in situ observations, they indicate that the upwelling is too fast in the tropical lower stratosphere. The spread between the five simulations in the northern midlatitudes is as large as the observational uncertainties in a multidecadal time series of balloon observations, i.e., approximately 2 years. No global impact of the Pinatubo eruption can be found in our simulations of AoA, contrary to a recent study which used a diabatic transport model driven by ERA-I and JRA-55 winds and heating rates. The time variations are also analyzed through multiple linear regression analyses taking into account the seasonal cycles, the quasi-biennial oscillation and the linear trends over four time periods. The amplitudes of AoA seasonal variations in the lower stratosphere are significantly larger when using MERRA and MERRA-2 than with the other reanalyses. The linear trends of AoA using ERA-I confirm those found by earlier model studies, especially for the period 2002–2012, where the dipole structure of the latitude–height distribution (positive in the northern midstratosphere and negative in the southern midstratosphere) also matches trends derived from satellite observations of SF6. Yet the linear trends vary substantially depending on the considered period. Over 2002–2015, the ERA-I results still show a dipole structure with positive trends in the Northern Hemisphere reaching up to 0.3yrdec−1. No reanalysis other than ERA-I finds any dipole structure of AoA trends. The signs of the trends depend strongly on the input reanalysis and on the considered period, with values above 10hPa varying between approximately −0.4 and 0.4yrdec−1. Using ERA-I and CFSR, the 2002–2015 trends are negative above 10hPa, but using the three other reanalyses these trends are positive. Over the whole period (1989–2015) each reanalysis delivers opposite trends; i.e., AoA is mostly increasing with CFSR and ERA-I but mostly decreasing with MERRA, JRA-55 and MERRA-2. In view of this large disagreement, we urge great caution for studies aiming to assess AoA trends derived only from reanalysis winds. We briefly discuss some possible causes for the dependency of AoA on the input reanalysis and highlight the need for complementary intercomparisons using diabatic transport models.

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See detailAtmospheric CO and CH4 time series and seasonal variations on Reunion Island from ground-based in situ and FTIR (NDACC and TCCON) measurements
Zhou, M.; Langerock, B.; Vigouroux, C.; Sha, M. K.; Ramonet, M.; Delmotte, M.; Mahieu, Emmanuel; Bader, Whitney; Hermans, C.; Kumps, N.; Metzger, J.-M.; Duflot, V.; Wang, Z.; Palm, M.; De Mazière, M.

in Atmospheric Chemistry and Physics (2018), 2018(18), 13881-13901

Atmospheric carbon monoxide (CO) and methane (CH4) mole fractions are measured by ground-based in situ cavity ring-down spectroscopy (CRDS) analyzers and Fourier transform infrared (FTIR) spectrometers at two sites (St Denis and Maïdo) on Reunion Island (21°S, 55°E) in the Indian Ocean. Currently, the FTIR Bruker IFS 125HR at St Denis records the direct solar spectra in the near-infrared range, contributing to the Total Carbon Column Observing Network (TCCON). The FTIR Bruker IFS 125HR at Maïdo records the direct solar spectra in the mid-infrared (MIR) range, contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). In order to understand the atmospheric CO and CH4 variability on Reunion Island, the time series and seasonal cycles of CO and CH4 from in situ and FTIR (NDACC and TCCON) measurements are analyzed. Meanwhile, the difference between the in situ and FTIR measurements are discussed. The CO seasonal cycles observed from the in situ measurements at Maïdo and FTIR retrievals at both St Denis and Maïdo are in good agreement with a peak in September–November, primarily driven by the emissions from biomass burning in Africa and South America. The dry-air column averaged mole fraction of CO (XCO) derived from the FTIR MIR spectra (NDACC) is about 15.7ppb larger than the CO mole fraction near the surface at Maïdo, because the air in the lower troposphere mainly comes from the Indian Ocean while the air in the middle and upper troposphere mainly comes from Africa and South America. The trend for CO on Reunion Island is unclear during the 2011–2017 period, and more data need to be collected to get a robust result. A very good agreement is observed in the tropospheric and stratospheric CH4 seasonal cycles between FTIR (NDACC and TCCON) measurements, and in situ and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite measurements, respectively. In the troposphere, the CH4 mole fraction is high in August–September and low in December–January, which is due to the OH seasonal variation. In the stratosphere, the CH4 mole fraction has its maximum in March–April and its minimum in August–October, which is dominated by vertical transport. In addition, the different CH4 mole fractions between the in situ, NDACC and TCCON CH4 measurements in the troposphere are discussed, and all measurements are in good agreement with the GEOS-Chem model simulation. The trend of XCH4 is 7.6±0.4ppbyr−1 from the TCCON measurements over the 2011 to 2017 time period, which is consistent with the CH4 trend of 7.4±0.5ppbyr−1 from the in situ measurements for the same time period at St Denis.

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See detailTropospheric Ozone Assessment Report: Present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation
Gaudel, A.; Cooper, O. R.; Ancellet, G.; Barret, B.; Boynard, A.; Burrows, J. P.; Clerbaux, C.; Coheur, P.-F.; Cuesta, J.; Cuevas, E.; Doniki, S.; Dufour, G.; Ebojie, F.; Foret, G.; Garcia, O.; Granados Muños, M. J.; Hannigan, J. W.; Hase, F.; Huang, G.; Hassler, B.; Hurtmans, D.; Jaffe, D.; Jones, N.; Kalabokas, P.; Kerridge, B.; Kulawik, S. S.; Latter, B.; Leblanc, T.; Le Flochmoën, E.; Lin, W.; Liu, Jian; Liu, X.; Mahieu, Emmanuel; McClure-Begley, A.; Neu, J. L.; Osman, M.; Palm, M.; Petetin, H.; Petropavlovskikh, I.; Querel, R.; Rahpoe, N.; Rozanov, A.; Schultz, M. G.; Schwab, J.; Siddans, R.; Smale, D.; Steinbacher, M.; Tanimoto, H.; Tarasick, D. W.; Thouret, V.; Thompson, A. M.; Trickl, T.; Weatherhead, E.; Wespes, C.; Worden, H. M.; Vigouroux, C.; Xu, X.; Zeng, G.; Ziemke, J.

in Elementa: Science of the Anthropocene (2018), 6(1), 39

The Tropospheric Ozone Assessment Report (TOAR) is an activity of the International Global Atmospheric Chemistry Project. This paper is a component of the report, focusing on the present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation. Utilizing the TOAR surface ozone database, several figures present the global distribution and trends of daytime average ozone at 2702 non-urban monitoring sites, highlighting the regions and seasons of the world with the greatest ozone levels. Similarly, ozonesonde and commercial aircraft observations reveal ozone’s distribution throughout the depth of the free troposphere. Long-term surface observations are limited in their global spatial coverage, but data from remote locations indicate that ozone in the 21st century is greater than during the 1970s and 1980s. While some remote sites and many sites in the heavily polluted regions of East Asia show ozone increases since 2000, many others show decreases and there is no clear global pattern for surface ozone changes since 2000. Two new satellite products provide detailed views of ozone in the lower troposphere across East Asia and Europe, revealing the full spatial extent of the spring and summer ozone enhancements across eastern China that cannot be assessed from limited surface observations. Sufficient data are now available (ozonesondes, satellite, aircraft) across the tropics from South America eastwards to the western Pacific Ocean, to indicate a likely tropospheric column ozone increase since the 1990s. The 2014–2016 mean tropospheric ozone burden (TOB) between 60˚N–60˚S from five satellite products is 300 Tg ± 4%. While this agreement is excellent, the products differ in their quantification of TOB trends and further work is required to reconcile the differences. Satellites can now estimate ozone’s global long-wave radiative effect, but evaluation is difficult due to limited in situ observations where the radiative effect is greatest.

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See detailGround-based FTIR retrievals of SF6 on Reunion Island
Zhou, M.; Langerock, B.; Vigouroux, C.; Wang, P.; Hermans, C.; Stiller, G.; Walker, K. A.; Dutton, G.; Mahieu, Emmanuel; De Mazière, M.

in Atmospheric Measurement Techniques (2018), 11

SF6 total columns were successfully retrieved from FTIR (Fourier transform infrared) measurements (Saint Denis and Maïdo) on Reunion Island (21º S, 55º E) between 2004 and 2016 using the SFIT4 algorithm: the retrieval strategy and the error budget were presented. The FTIR SF6 retrieval has independent information in only one individual layer, covering the whole of the troposphere and the lower stratosphere. The trend in SF6 was analysed based on the FTIR-retrieved dry-air column-averaged mole fractions (XSF6 ) on Reunion Island, the in situ measurements at America Samoa (SMO) and the collocated satellite measurements (Michelson Interferometer for Passive Atmospheric Sounding, MIPAS, and Atmospheric Chemistry Experiment Fourier Transform Spectrometer, ACE-FTS) in the southern tropics. The SF6 annual growth rate from FTIR retrievals is 0.265±0.013 pptv year-1 for 2004–2016, which is slightly weaker than that from the SMO in situ measurements (0.285±0.002 pptv year-1) for the same time period. The SF6 trend in the troposphere from MIPAS and ACE-FTS observations is also close to the ones from the FTIR retrievals and the SMO in situ measurements.

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See detailSurveillance de l'atmosphère terrestre depuis la station du Jungfraujoch : une épopée liégeoise entamée voici plus de 65 ans !
Mahieu, Emmanuel; Bader, Whitney; Bovy, Benoît; Demoulin, Philippe; Flock, Olivier; Franco, Bruno; Lejeune, Bernard; Prignon, Maxime; Roland, G; Servais, Christian

in Bulletin de la Société Géographique de Liège (2017), 68

It’s in the early 1950s that researchers from the University of Liège started to investigate the Earth’s atmosphere from the Jungfraujoch scientific station, in the Swiss Alps, at a time when concerns related to atmospheric composition changes were nonexistent. Since then, an infrared observational data base unique worldwide has been carefully collected. The exploitation of these observations has allowed constituting multi-decadal time series crucial for the characterization of the changes that affected our atmosphere and for the identification of their causes. In this paper, we first remind about the successive steps which led to establishing the observational program of the Liège team at the Jungfraujoch and we evoke important findings which justified its continuation. Then we present some recent results relevant to the Montreal and Kyoto Protocols, or related to the monitoring of air quality.

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See detailComparison of the GOSAT TANSO-FTS TIR CH4 volume mixing ratio vertical profiles with those measured by ACE-FTS, ESA MIPAS, IMK-IAA MIPAS, and 16 NDACC stations
Olsen, Kevin S; Strong, Kimberley; Walker, Kaley; Boone, Chris D; Raspollini, P; Bader, Whitney; Conway, Stephanie; Grutter, Michel; Hannigan, James W; Hase, Frank; Jones, Nicholas; de Mazière, Martine; Schneider, Matthias; Smale, Dan; Sussmann, Ralf; Saitoh, Naoko

in Atmospheric Measurement Techniques (2017), 10

The primary instrument on the Greenhouse gases Observing SATellite (GOSAT) is the Thermal And Near infrared Sensor for carbon Observations (TANSO) Fourier transform spectrometer (FTS). TANSO-FTS uses three short-wave infrared (SWIR) bands to retrieve total columns of CO2 and CH4 along its optical line of sight and one thermal infrared (TIR) channel to retrieve vertical profiles of CO2 and CH4 volume mixing ratios (VMRs) in the troposphere. We examine version 1 of the TANSO-FTS TIR CH4 product by comparing co-located CH4 VMR vertical profiles from two other remote-sensing FTS systems: the Canadian Space Agency's Atmospheric Chemistry Experiment FTS (ACE-FTS) on SCISAT (version 3.5) and the European Space Agency's Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat (ESA ML2PP version 6 and IMK-IAA reduced-resolution version V5R_CH4_224/225), as well as 16 ground stations with the Network for the Detection of Atmospheric Composition Change (NDACC). This work follows an initial inter-comparison study over the Arctic, which incorporated a ground-based FTS at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Canada, and focuses on tropospheric and lower-stratospheric measurements made at middle and tropical latitudes between 2009 and 2013 (mid-2012 for MIPAS). For comparison, vertical profiles from all instruments are interpolated onto a common pressure grid, and smoothing is applied to ACE-FTS, MIPAS, and NDACC vertical profiles. Smoothing is needed to account for differences between the vertical resolution of each instrument and differences in the dependence on a priori profiles. The smoothing operators use the TANSO-FTS a priori and averaging kernels in all cases. We present zonally averaged mean CH4 differences between each instrument and TANSO-FTS with and without smoothing, and we examine their information content, their sensitive altitude range, their correlation, their a priori dependence, and the variability within each data set. Partial columns are calculated from the VMR vertical profiles, and their correlations are examined. We find that the TANSO-FTS vertical profiles agree with the ACE-FTS and both MIPAS retrievals' vertical profiles within 4 % (± ∼  40 ppbv) below 15 km when smoothing is applied to the profiles from instruments with finer vertical resolution but that the relative differences can increase to on the order of 25 % when no smoothing is applied. Computed partial columns are tightly correlated for each pair of data sets. We investigate whether the difference between TANSO-FTS and other CH4 VMR data products varies with latitude. Our study reveals a small dependence of around 0.1 % per 10 degrees latitude, with smaller differences over the tropics and greater differences towards the poles.

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See detailAn update on ozone profile trends for the period 2000 to 2016
Steinbrecht, Wolfgang; Froidevaux, Lucien; Fuller, Ryan; Wang, Ray; Anderson, John; Roth, Chris; Bourassa, Adam; Degenstein, Doug; Damadeo, Robert; Zawodny, Joseph; Frith, Stacey; McPeters, Richard; Bhartia, Pawan; Wild, Jeannette; Long, Craig; Davis, Sean; Rosenlof, Karen; Sofieva, Viktoria; Walker, Kaley; Rahpoe, Nabiz; Rozanov, Alexei; Weber, Mark; Laeng, Alexandra; von Clarmann, Thomas; Stiller, Gabriele; Kramarova, Natalya; Godin-Beekmann, Sophie; Leblanc, Thierry; Querel, Richard; Swart, Daan; Boyd, Ian; Hocke, Klemens; Kämpfer, Niklaus; Maillard Barras, Eliane; Moreira, Lorena; Nedoluha, Gerald; Vigouroux, Corinne; Blumenstock, Thomas; Schneider, Matthias; Garcìa, Omaira; Jones, Nicholas; Mahieu, Emmanuel; Smale, Dan; Kotkamp, Michael; Robinson, John; Petropavlovskikh, Irina; Harris, Neil; Hassler, Birgit; Hubert, Daan; Tummon, Fiona

in Atmospheric Chemistry and Physics (2017), 17(17), 10675-10690

Ozone profile trends over the period 2000 to 2016 from several merged satellite ozone data sets and from ground-based data by four techniques at stations of the Network for the Detection of Atmospheric Composition Change indicate significant ozone increases in the upper stratosphere, between 35 and 48 km altitude (5 and 1 hPa). Near 2 hPa (42 km), ozone has been increasing by about 1.5 % per decade in the tropics (20°S to 20°N), and by 2 to 2.5 % per decade in the 35° to 60° latitude bands of both hemispheres. At levels below 35 km (5 hPa), 2000 to 2016 ozone trends are smaller and not statistically significant. The observed trend profiles are consistent with expectations from chemistry climate model simulations. Using three to four more years of observations and updated data sets, this study confirms positive trends of upper stratospheric ozone already reported, e.g., in the WMO/UNEP Ozone Assessment 2014, or by Harris et al. (2015). The additional years, and the fact that nearly all individual data sets indicate these increases, give enhanced confidence. Nevertheless, a thorough analysis of possible drifts and differences between various data sources is still required, as is a detailed attribution of the observed increases to declining ozone depleting substances and to stratospheric cooling. Ongoing quality observations from multiple independent platforms are key for verifying that recovery of the ozone layer continues as expected.

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See detailValidation of MOPITT carbon monoxide using ground-based Fourier transform infrared spectrometer data from NDACC
Buchholz, R. R.; Deeter, M. N.; Worden, H. M.; Gille, J.; Edwards, D. P.; Hannigan, J. W.; Jones, N. B.; Paton-Walsh, C.; Griffith, D. W. T.; Smale, D.; Robinson, J.; Strong, K.; Conway, S.; Sussmann, R.; Hase, F.; Blumenstock, T.; Mahieu, Emmanuel; Langerock, B.

in Atmospheric Measurement Techniques (2017), 10(5), 1927--1956

The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument provides the longest continuous dataset of carbon monoxide (CO) from space. We perform the first validation of MOPITT version 6 retrievals using total column CO measurements from ground-based remote-sensing Fourier transform infrared spectrometers (FTSs). Validation uses data recorded at 14 stations, that span a wide range of latitudes (80°N to 78°S), in the Network for the Detection of Atmospheric Composition Change (NDACC). MOPITT measurements are spatially co-located with each station, and different vertical sensitivities between instruments are accounted for by using MOPITT averaging kernels (AKs). All three MOPITT retrieval types are analyzed: thermal infrared (TIR-only), joint thermal and near infrared (TIR–NIR), and near infrared (NIR-only). Generally, MOPITT measurements overestimate CO relative to FTS measurements, but the bias is typically less than 10%. Mean bias is 2.4% for TIR-only, 5.1% for TIR–NIR, and 6.5% for NIR-only. The TIR–NIR and NIR-only products consistently produce a larger bias and lower correlation than the TIR-only. Validation performance of MOPITT for TIR-only and TIR–NIR retrievals over land or water scenes is equivalent. The four MOPITT detector element pixels are validated separately to account for their different uncertainty characteristics. Pixel 1 produces the highest standard deviation and lowest correlation for all three MOPITT products. However, for TIR-only and TIR–NIR, the error-weighted average that includes all four pixels often provides the best correlation, indicating compensating pixel biases and well-captured error characteristics. We find that MOPITT bias does not depend on latitude but rather is influenced by the proximity to rapidly changing atmospheric CO. MOPITT bias drift has been bound geographically to within ±0.5%/yr or lower at almost all locations.

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See detailRevisiting global fossil fuel and biofuel emissions of ethane
Tzompa-Sosa, Z. A.; Mahieu, Emmanuel; Franco, Bruno; Keller, C. A.; Turner, A. J.; Helmig, D.; Fried, A.; Richter, D.; Weibring, P.; Walega, J.; Yacovitch, T. I.; Herndon, S. C.; Blake, D. R.; Hase, F.; Hannigan, J. W.; Conway, S.; Strong, K.; Schneider, M.; Fischer, E. V.

in Journal of Geophysical Research. Atmospheres (2017), 122(4), 2493--2512

Recent measurements over the Northern Hemisphere indicate that the long-term decline in the atmospheric burden of ethane (C2H6) has ended and the abundance increased dramatically between 2010 and 2014. The rise in C2H6 atmospheric abundances has been attributed to oil and natural gas extraction in North America. Existing global C2H6 emission inventories are based on outdated activity maps that do not account for current oil and natural gas exploitation regions. We present an updated global C2H6 emission inventory based on 2010 satellite-derived CH4 fluxes with adjusted C2H6 emissions over the U.S. from the National Emission Inventory (NEI 2011). We contrast our global 2010 C2H6 emission inventory with one developed for 2001. The C2H6 difference between global anthropogenic emissions is subtle (7.9 versus 7.2 Tg yr−1), but the spatial distribution of the emissions is distinct. In the 2010 C2H6 inventory, fossil fuel sources in the Northern Hemisphere represent half of global C2H6 emissions and 95% of global fossil fuel emissions. Over the U.S., unadjusted NEI 2011 C2H6 emissions produce mixing ratios that are 14–50% of those observed by aircraft observations (2008–2014). When the NEI 2011 C2H6 emission totals are scaled by a factor of 1.4, the Goddard Earth Observing System Chem model largely reproduces a regional suite of observations, with the exception of the central U.S., where it continues to underpredict observed mixing ratios in the lower troposphere. We estimate monthly mean contributions of fossil fuel C2H6 emissions to ozone and peroxyacetyl nitrate surface mixing ratios over North America of ~1% and ~8%, respectively.

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See detailThe recent increase of atmospheric methane from 10 years of ground-based NDACC FTIR observations since 2005
Bader, Whitney; Bovy, Benoît; Conway, Stephanie; Strong, Kimberly; Smale, Dan; Turner, Alexander J.; Blumenstock, Thomas; Boone, Chris; Coulon, Ancelin; Garcia, Omaira; Griffith, David W. T.; Hase, Franck; Haussmann, Petra; Jones, Nicholas; Krummel, Paul; Murata; Morino, Isamu; Nakajima, Hideaki; O'Doherty, Simon; Paton-Walsh, Clare; Robinson, John; Sandrin, Rodrigue; Schneider, Matthias; Servais, Christian; Sussmann, Ralf; Mahieu, Emmanuel

in Atmospheric Chemistry and Physics (2017)

Changes of atmospheric methane total columns (CH4/ since 2005 have been evaluated using Fourier transform infrared (FTIR) solar observations carried out at 10 ground-based sites, affiliated to the Network for Detection of Atmospheric Composition Change (NDACC). From this, we find an increase of atmospheric methane total columns of 0.31±0.03 %/year (2-sigma level of uncertainty) for the 2005–2014 period. Comparisons with in situ methane measurements at both local and global scales show good 10 agreement. We used the GEOS-Chem chemical transport model tagged simulation, which accounts for the contribution of each emission source and one sink in the total methane, simulated over 2005–2012. After regridding according to NDACC vertical layering using a conservative 15 regridding scheme and smoothing by convolving with respective FTIR seasonal averaging kernels, the GEOS-Chem simulation shows an increase of atmospheric methane total columns of 0.35±0.03 %/year between 2005 and 2012, which is in agreement with NDACC measurements over the same time period (0.30±0.04 %/year, averaged over 10 stations). Analysis of the GEOS-Chem-tagged simulation allows us to quantify the contribution of each tracer to the global methane change since 2005. We find that natural sources such as wetlands and biomass burning contribute to the interannual variability of methane. However, anthropogenic emissions, such as coal mining, and gas and oil transport and exploration, which are mainly emitted in the Northern Hemisphere and act as secondary contributors to the global budget of methane, have played a major role in the increase of atmospheric methane observed since 2005. Based on the GEOS-Chem-tagged simulation, we discuss possible cause(s) for the increase of methane since 2005, which is still unexplained.

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See detailTropospheric water vapour isotopologue data (H216O, H218O and HD16O) as obtained from NDACC/FTIR solar absorption spectra
Barthlott, Sabine; Schneider, Matthias; Hase, Frank; Blumenstock, Thomas; Kiel, Matthäus; Dubravica, Darko; García, Omaira E.; Sepúlveda, Eliezer; Mengistu Tsidu, Gizaw; Takele Kenea, Samuel; Grutter, Michel; Plaza-Medina, Eddy F.; Stremme, Wolfgang; Strong, Kim; Weaver, Dan; Palm, Mathias; Warneke, Thorsten; Notholt, Justus; Mahieu, Emmanuel; Servais, Christian; Jones, Nicholas; Griffith, David W. T.; Smale, Dan; Robinson, John

in Earth System Science Data (2017), 9

We report on the ground-based FTIR (Fourier Transform InfraRed) tropospheric water vapour isotopologue remote sensing data that have been recently made available via the database of NDACC (Network for the Detection of Atmospheric Composition Change; ftp://ftp.cpc.ncep.noaa.gov/ndacc/MUSICA/) and via doi:10.5281/zenodo.48902. Currently, data are available for 12 globally distributed stations. They have been centrally retrieved and quality filtered in the framework of the MUSICA project (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water). We explain particularities of retrieving the water vapour isotopologue state (vertical distribution of H162O, H182O and HD16O) and reveal the need for a new meta-data template for archiving FTIR isotopologue data. We describe the format of different data components and give recommendations for correct data usage. Data are provided as two data types. The first type is best-suited for tropospheric water vapour distribution studies disregarding different isotopologues (comparison with radiosonde data, analyses of water vapour variability and trends, etc.). The second type is needed for analysing moisture pathways by means of {H2O,delta-D}-pair distributions.

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See detailOptimized approach to retrieve information on atmospheric carbonyl sulfide (OCS) above the Jungfraujoch station and change in its abundance since 1995
Lejeune, Bernard; Mahieu, Emmanuel; Vollmer, M. K.; Reimann, S.; Bernath, P. F.; Boone, C. D.; Walker, K. A.; Servais, Christian

in Journal of Quantitative Spectroscopy and Radiative Transfer (2017), 186

In this paper, we present an optimized retrieval strategy for carbonyl sulfide (OCS), using Fourier transform infrared (FTIR) solar observations made at the high-altitude Jungfraujoch station in the Swiss Alps. More than 200 lines of the nu3 fundamental band of OCS have been systematically evaluated and we selected 4 microwindows on the basis of objective criteria minimizing the effect of interferences, mainly by solar features, carbon dioxide and water vapor absorption lines, while maximizing the information content. Implementation of this new retrieval strategy provided an extended time series of the OCS abundance spanning the 1995-2015 time period, for the study of the long-term trend and seasonal variation of OCS in the free troposphere and stratosphere. Three distinct periods characterize the evolution of the tropospheric partial columns: a first decreasing period (1995-2002), an intermediate increasing period (2002-2008), and the more recent period (2008-2015) which shows no significant trend. Our FTIR tropospheric and stratospheric time series are compared with new in situ gas chromatography mass spectrometry (GCMS) measurements performed by Empa (Laboratory for Air Pollution/Environmental Technology) at the Jungfraujoch since 2008, and with space-borne solar occultation observations by the ACE-FTS instrument on-board the SCISAT satellite, respectively, and they show good agreement. The OCS signal recorded above Jungfraujoch appears to be closely related to anthropogenic sulfur emissions.

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See detailModel Sensitivity Studies of the Decrease in Atmospheric Carbon Tetrachloride
Chipperfield, M. P.; Liang, Q.; Rigby, M.; Hossaini, R.; Montzka, S. A.; Dhomse, S.; Feng, W.; Prinn, R. G.; Weiss, R. F.; Harth, C. M.; Salameh, P. K.; Mühle, J.; O'Doherty, S.; Young, D.; Simmonds, P. G.; Krummel, P. B.; Fraser, P. J.; Steele, L. P.; Happell, J. D.; Rhew, R. C.; Butler, J.; Yvon-Lewis, S. A.; Hall, B.; Nance, D.; Moore, F.; Miller, B. R.; Elkins, J. W.; Harrison, J. J.; Boone, C. D.; Atlas, E. L.; Mahieu, Emmanuel

in Atmospheric Chemistry and Physics (2016), 16

Carbon tetrachloride is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this decrease is known to be slower than expected based on reported CCl4 emissions and its estimated overall atmospheric lifetime. Here we use a three-dimensional (3-D) chemical transport model to investigate the impact on its predicted decay of uncertainties in the rates at which CCl4 is removed from the atmosphere by photolysis, by ocean uptake and by degradation in soils. The largest sink is atmospheric photolysis (76% of total) but a reported 10% uncertainty in its combined photolysis cross-section and quantum yield has only a modest impact on the modelled rate of CCl4 decay. This is partly due to the limiting effect of the rate of transport of CCl4 from the main tropospheric reservoir to the stratosphere where photolytic loss occurs. The model suggests large interannual variability in the magnitude of this stratospheric photolysis sink caused by variations in transport. The impact of uncertainty in the minor soil sink (9% of total) is also relatively small. In contrast, the model shows that uncertainty in ocean loss (15% of total) has the largest impact on modelled CCl4 decay due to its sizeable contribution to CCl4 loss and large uncertainty range (157 to 313 years). With an assumed CCl4 emission rate of 39 Gg/yr, the reference simulation with best estimate of loss processes still underestimates the observed CCl4 (overestimates the decay) over the past two decades but to a smaller extent than previous studies. Changes to the rate of CCl4 loss processes, in line with known uncertainties, could bring the model into agreement with in situ surface and remote-sensing measurements, as could an increase in emissions to around 45 Gg/yr. Further progress in constraining the CCl4 budget is partly limited by systematic biases between observational datasets. For example, surface observations from the NOAA network are larger than from the AGAGE network but have shown a steeper decreasing trend over the past two decades. These differences imply a difference in emissions which is significant relative to uncertainties in the magnitudes of the CCl4 sinks.

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See detailFirst characterization and validation of FORLI-HNO3 vertical profiles retrieved from IASI/Metop
Ronsmans, G.; Langerock, B.; Wespes, C.; Hannigan, J. W.; Hase, F.; Kerzenmacher, T.; Mahieu, Emmanuel; Schneider, M.; Smale, D.; Hurtmans, D.; De Mazière, M.; Clerbaux, C.; Coheur, P.-F.

in Atmospheric Measurement Techniques (2016), 16

Knowing the spatial and seasonal distributions of nitric acid (HNO3) around the globe is of great interest to apprehend the processes regulating stratospheric ozone, especially in the polar regions. Thanks to its unprecedented spatial and temporal sampling, the nadir-viewing Infrared Atmospheric Sounding Interferometer (IASI) allows sounding the atmosphere twice a day globally, with good spectral resolution and low noise. With the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, we are retrieving, in near-real time, columns as well as vertical profiles of several atmospheric species, amongst which is HNO3. We present in this paper the first characterization of the FORLI-HNO3 profile products, in terms of vertical sensitivity and error budgets. We show that the sensitivity of IASI to HNO3 is highest in the lower stratosphere (10–20km), where the largest amounts of HNO3 are found, but that the vertical sensitivity of IASI only allows one level of information on the profile (DOFS 1). The sensitivity near the surface is negligible in most cases, and for this reason, a partial column (5–35km) is used for the analyses. Both vertical profiles and partial columns are compared to FTIR ground-based measurements from the Network for the Detection of Atmospheric Composition Change (NDACC) to characterize the accuracy and precision of the FORLI-HNO3 product. The profile validation is conducted through the smoothing of the raw FTIR profiles by the IASI averaging kernels and gives good results, with a slight overestimation of IASI measurements in the Upper Troposphere-Lower Stratosphere (UTLS) at the 6 chosen stations (Thule, Kiruna, Jungfraujoch, Izaña, Lauder and Arrival Heights). The validation of the partial columns (5–35km) is also conclusive with a mean correlation of 0.93 between IASI and the FTIR measurements. An initial survey of the HNO3 spatial and seasonal variabilities obtained from IASI measurements for a one year (2011) data set shows that the expected latitudinal gradient of concentrations from low to high latitudes and the large seasonal variability in polar regions (cycle amplitude around 30% of the seasonal signal, peak-to-peak) are well represented with IASI data.

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See detailSeasonal variability of surface and column carbon monoxide over megacity Paris, high-altitude Jungfraujoch and Southern Hemispheric Wollongong stations
Té, Y; Jeseck, P; Franco, Bruno; Mahieu, Emmanuel; Jones, N; Paton-Walsh, C; Griffith, D W T; Buchholz, R R; Hadji-Lazaro, J; Hurtmans, D; Janssen, C

in Atmospheric Chemistry and Physics (2016), 16

This paper studies the seasonal variation of surface and column CO at three different sites (Paris, Jungfraujoch and Wollongong), with an emphasis on establishing a link between the CO vertical distribution and the nature of CO emission sources. We find the first evidence of a time lag between surface and free tropospheric CO seasonal variations in the Northern Hemisphere. The CO seasonal variability obtained from the total columns and free tropospheric partial columns shows a maximum around March–April and a minimum around September–October in the Northern Hemisphere (Paris and Jungfraujoch). In the Southern Hemisphere (Wollongong) this seasonal variability is shifted by about 6 months. Satellite observations by the IASI–MetOp (Infrared Atmospheric Sounding Interferometer) and MOPITT (Measurements Of Pollution In The Troposphere) instruments confirm this seasonality. Ground-based FTIR (Fourier transform infrared) measurements provide useful complementary information due to good sensitivity in the boundary layer. In situ surface measurements of CO volume mixing ratios at the Paris and Jungfraujoch sites reveal a time lag of the near-surface seasonal variability of about 2 months with respect to the total column variability at the same sites. The chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model) is employed to interpret our observations. GEOS-Chem sensitivity runs identify the emission sources influencing the seasonal variation of CO. At both Paris and Jungfraujoch, the surface seasonality is mainly driven by anthropogenic emissions, while the total column seasonality is also controlled by air masses transported from distant sources. At Wollongong, where the CO seasonality is mainly affected by biomass burning, no time shift is observed between surface measurements and total column data.

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See detailIntercomparison of in-situ NDIR and column FTIR measurements of CO2 at Jungfraujoch
Schibig, M. F.; Mahieu, Emmanuel; Henne, S.; Lejeune, Bernard; Leuenberger, M. C.

in Atmospheric Chemistry and Physics (2016), 16(15), 9935--9949

We compare two CO2 time series measured at the High Alpine Research Station Jungfraujoch, Switzerland (3580 m a.s.l.), in the period from 2005 to 2013 with an in situ surface measurement system using a nondispersive infrared analyzer (NDIR) and a ground-based remote sensing system using solar absorption Fourier transform infrared (FTIR) spectrometry. Although the two data sets show an absolute shift of about 13 ppm, the slopes of the annual CO2 increase are in good agreement within their uncertainties. They are 2.04±0.07 and 1.97±0.05 ppm yr-1 for the FTIR and the NDIR systems, respectively. The seasonality of the FTIR and the NDIR systems is 4.46±1.11 and 10.10±0.73 ppm, respectively. The difference is caused by a dampening of the CO2 signal with increasing altitude due to mixing processes. Whereas the minima of both data series occur in the middle of August, the maxima of the two data sets differ by about 10 weeks; the maximum of the FTIR measurements is in the middle of January, and the maximum of the NDIR measurements is found at the end of March. Sensitivity analyses revealed that the air masses measured by the NDIR system at the surface of Jungfraujoch are mainly influenced by central Europe, whereas the air masses measured by the FTIR system in the column above Jungfraujoch are influenced by regions as far west as the Caribbean and the USA. The correlation between the hourly averaged CO2 values of the NDIR system and the individual FTIR CO2 measurements is 0.820, which is very encouraging given the largely different sampling volumes. Further correlation analyses showed, that the correlation is mainly driven by the annual CO2 increase and to a lesser degree by the seasonality. Both systems are suitable to monitor the long-term CO2 increase, because this signal is represented in the whole atmosphere due to mixing.

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See detailHCOOH distributions from IASI for 2008-2014: comparison with ground-based FTIR measurements and a global chemistry-transport model
Pommier, M.; Clerbaux, C.; Coheur, P.-F.; Mahieu, Emmanuel; Müller, J.-F.; Paton-Walsh, C.; Stavrakou, T.; Vigouroux, C.

in Atmospheric Chemistry and Physics (2016), 16

Formic acid (HCOOH) is one of the most abundant volatile organic compounds in the atmosphere. It is a major contributor to rain acidity in remote areas. There are, however, large uncertainties on the sources and sinks of HCOOH and therefore HCOOH is misrepresented by global chemistry-transport models. This work presents global distributions from 2008 to 2014 as derived from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI), based on conversion factors between brightness temperature differences and representative retrieved total columns over seven regions: Northern Africa, southern Africa, Amazonia, Atlantic, Australia, Pacific, and Russia. The dependence of the measured HCOOH signal on the thermal contrast is taken into account in the conversion method. This conversion presents errors lower than 20 % for total columns ranging between 0.5 and 1 × 1016 molec/cm2 but reaches higher values, up to 78 %, for columns that are lower than 0.3 × 1016 molec/cm2. Signatures from biomass burning events are highlighted, such as in the Southern Hemisphere and in Russia, as well as biogenic emission sources, e.g., over the eastern USA. A comparison between 2008 and 2014 with ground-based Fourier transform infrared spectroscopy (FTIR) measurements obtained at four locations (Maido and Saint-Denis at La Réunion, Jungfraujoch, and Wollongong) is shown. Although IASI columns are found to correlate well with FTIR data, a large bias (> 100 %) is found over the two sites at La Réunion. A better agreement is found at Wollongong with a negligible bias. The comparison also highlights the difficulty of retrieving total columns from IASI measurements over mountainous regions such as Jungfraujoch. A comparison of the retrieved columns with the global chemistry-transport model IMAGESv2 is also presented, showing good representation of the seasonal and interannual cycles over America, Australia, Asia, and Siberia. A global model underestimation of the distribution and a misrepresentation of the seasonal cycle over India are also found. A small positive trend in the IASI columns is observed over Australia, Amazonia, and India over the 2008–2014 period (from 0.7 to 1.5 %/year), while a decrease of ∼ 0.8 %/year is measured over Siberia.

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See detailSPARC Report on the Mystery of Carbon Tetrachloride
Ahmadzai, H; Bock, R P; Burkholder, J B; Butler, J H; Chatterjee, A; Chipperfield, M P; Daniel, J S; Derek, N; Fleming, E L; Fraser, P J; Graziosi, F; Hall, B; Hannigan, J W; Happell, J; Harrison, J J; Hu, J; Hu, L; Jucks, K W; Kinnison, D E; Kuijpers, L; Kurylo, M J; Lezeaux, O; Liang, Q; Lupo, F; Mahieu, Emmanuel; Maione, M; McCulloch, A; Montzka, S A; Newman, P A; Odabasi, M; Ohnishi, K; Park, S; Reimann, S; Rhew, R C; Rigby, M; Sherry, D; Simpson, I J; Singh, H B; Suntharalingam, P; Tummon, F; Tellaexte, I U; von Clarmann, T; Weiss, R F; Yao, B; Yvon-Lewis, S A; Zhou, L

in Liang, Qing; Newman, Paul A; Reimann, Stefan (Eds.) SPARC Report on the Mystery of Carbon Tetrachloride (2016)

The Montreal Protocol (MP) controls the production and consumption of carbon tetrachloride (CCl4 or CTC) and other ozone-depleting substances (ODSs) for emissive uses. CCl4 is a major ODS, accounting for about 12% of the globally averaged inorganic chlorine and bromine in the stratosphere, compared to 14% for CFC-12 in 2012. In spite of the MP controls, there are large ongoing emissions of CCl4 into the atmosphere. Estimates of emissions from various techniques ought to yield similar numbers. However, the recent WMO/UNEP Scientific Assessment of Ozone Depletion [WMO, 2014] estimated a 2007-2012 CCl4 bottom-up emission of 1-4 Gg/year (1-4 kilotonnes/year), based on country-by-country reports to UNEP, and a global top-down emissions estimate of 57 Gg/ year, based on atmospheric measurements. This 54 Gg/year difference has not been explained. In order to assess the current knowledge on global CCl4 sources and sinks, stakeholders from industrial, governmental, and the scientific communities came together at the “Solving the Mystery of Carbon Tetrachloride” workshop, which was held from 4-6 October 2015 at Empa in Dübendorf, Switzerland. During this workshop, several new findings were brought forward by the participants on CCl4 emissions and related science. • Anthropogenic production and consumption for feedstock and process agent uses (e.g., as approved solvents) are reported to UNEP under the MP. Based on these numbers, global bottom-up emissions of 3 (0-8) Gg/year are estimated for 2007-2013 in this report. This number is also reasonably consistent with this report’s new industry-based bottom-up estimate for fugitive emissions of 2 Gg/year. • By-product emissions from chloromethanes and perchloroethylene plants are newly proposed in this report as significant CCl4 sources, with global emissions estimated from these plants to be 13 Gg/year in 2014. • This report updates the anthropogenic CCl4 emissions estimation as a maximum of ~25 Gg/year. This number is derived by combining the above fugitive and by-product emissions (2 Gg/year and 13 Gg/year, respectively) with 10 Gg/year from legacy emissions plus potential unreported inadvertent emissions from other sources. • Ongoing atmospheric CCl4 measurements within global networks have been exploited for assessing regional emissions. In addition to existing emissions estimates from China and Australia, the workshop prompted research on emissions in the U.S. and Europe. The sum of these four regional emissions is estimated as 21±7.5a Gg/year, but this is not a complete global accounting. These regional top-down emissions estimates also show that most of the CCl4 emissions originate from chemical industrial regions, and are not linked to major population centres. • The total CCl4 lifetime is critical for calculating top-down global emissions. CCl4 is destroyed in the stratosphere, oceans, and soils, complicating the total lifetime estimate. The atmospheric lifetime with respect to stratospheric loss was recently revised to 44 (36-58) years, and remains unchanged in this report. New findings from additional measurement campaigns and reanalysis of physical parameters lead to changes in the ocean lifetime from 94 years to 210 (157-313) years, and in the soil lifetime from 195 years to 375 (288-536) years. • These revised lifetimes lead to an increase of the total lifetime from 26 years in WMO [2014] to 33 (28-41) years. Consequently, CCl4 is lost at a slower rate from the atmosphere. With this new total lifetime, the global top-down emissions calculation decreases from 57 (40-74) Gg/year in WMO [2014] to 40 (25-55) Gg/year. This estimate is relatively consistent with the independent gradient top-down emissions of 30 (25-35) Gg/year, based upon differences between atmospheric measurements of CCl4 in the Northern and Southern Hemispheres. In addition, this new total lifetime implies an upper limit of 3-4 Gg/year of natural emissions, based upon newly reported observations of old air in firn snow. These new CCl4 emissions estimates from the workshop make considerable progress toward closing the emissions discrepancy. The new industrial bottom-up emissions estimate (15 Gg/year total) includes emissions from chloromethanes plants (13 Gg/year) and feedstock fugitive emissions (2 Gg/year). When combined with legacy emissions and unreported inadvertent emissions, this could be up to 25 Gg/year. Top-down emissions estimates are: global 40 (25-55) Gg/year, gradient 30 (25-35) Gg/year, and regional 21 (14-28) Gg/year. While the new bottom-up value is still less than the aggregated top-down values, these estimates reconcile the CCl4 budget discrepancy when considered at the edges of their uncertainties.

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See detailReversal of global atmospheric ethane and propane trends largely due to US oil and natural gas production
Helmig, Detlev; Rossabi, Samuel; Hueber, Jacques; Tans, Pieter; Montzka, Stephen A.; Masarie, Ken; Thoning, Kirk; Plass-Duelmer, Christian; Claude, Anja; Carpenter, Lucy J.; Lewis, Alastair C.; Punjabi, Shalini; Reimann, Stefan; Vollmer, Martin K.; Steinbrecher, Rainer; Hannigan, James W.; Emmons, Louisa K.; Mahieu, Emmanuel; Franco, Bruno; Smale, Dan; Pozzer, Andrea

in Nature Geoscience (2016)

Non-methane hydrocarbons such as ethane are important precursors to tropospheric ozone and aerosols. Using data from a global surface network and atmospheric column observations we show that the steady decline in ethane concentrations that began in the 1970s halted between 2005 and 2010 in most of the Northern Hemisphere, and has since reversed. We calculate a yearly increase in ethane emissions in the Northern Hemisphere of 0.42 (+/-0.19) Tg/yr between mid-2009 and mid-2014. The largest increases in ethane and for the shorter-lived propane are seen over the central and eastern USA, with a spatial distribution that suggests North American oil and natural gas development as the primary source of increasing emissions. By including other co-emitted oil and natural gas non-methane hydrocarbons, we estimate a Northern Hemisphere total non-methane hydrocarbon yearly emission increase of 1.2 (+/-0.8) Tg/yr. Atmospheric chemical transport modelling suggests that these emissions could augment summertime mean surface ozone by several nanomoles per mole near oil and natural gas production regions. Methane/ethane oil and natural gas emission ratios suggest a significant increase in associated methane emissions; however, this increase is inconsistent with observed leak rates in production regions and changes in methane’s global isotopic ratio.

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See detailEvaluating ethane and methane emissions associated with the development of oil and natural gas extraction in North America
Franco, Bruno; Mahieu, Emmanuel; Emmons, L. K.; Tzompa-Sosa, Z. A.; Fischer, E. V.; Sudo, K.; Bovy, Benoît; Conway, S.; Griffin, D.; Hannigan, J. W.; Strong, K.; Walker, K. A.

in Environmental Research Letters (2016), 11(4), 044010

Sharp rises in the atmospheric abundance of ethane (C2H6) have been detected from 2009 onwards in the Northern Hemisphere as a result of the unprecedented growth in the exploitation of shale gas and tight oil reservoirs in North America. Using time series of C2H6 total columns derived from ground-based FTIR observations made at five selected NDACC sites, we characterize the recent C2H6 evolution and determine growth rates of ~5%/yr at mid-latitudes and of ~3%/yr at remote sites. Results from CAM-chem simulations with the HTAP2 bottom-up inventory for anthropogenic emissions are found to greatly underestimate the current C2H6 abundances. Doubling global emissions is required to reconcile the simulations and the observations prior to 2009. We further estimate that North American anthropogenic C2H6 emissions have increased from 1.6 Tg/yr in 2008 to 2.8 Tg/yr in 2014, i.e. by 75% over these six years. We also completed a second simulation with new top-down emissions of C2H6 from North American oil and gas activities, biofuel consumption and biomass burning, inferred from space-borne observations of methane (CH4) from GOSAT. In this simulation, GEOS-Chem is able to reproduce FTIR measurements at the mid-latitudinal sites, underscoring the impact of the North American oil and gas development on the current C2H6 abundance. Finally we estimate that the North American oil and gas emissions of CH4, a major greenhouse gas, grew from 20 to 35 Tg/yr over the period 2008 to 2014, in association with the recent C2H6 rise.

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See detailDiurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N
Franco, Bruno; Marais, Eloise A.; Bovy, Benoît; Bader, Whitney; Lejeune, Bernard; Roland, Ginette; Servais, Christian; Mahieu, Emmanuel

in Atmospheric Chemistry and Physics (2016), 16

Only very few long-term records of formaldehyde (HCHO) exist that are suitable for trend analysis. Furthermore, many uncertainties remain as to its diurnal cycle, representing a large short-term variability superimposed on seasonal and inter-annual variations that should be accounted for when comparing ground-based observations to e.g., model results. In this study, we derive a multi-decadal time series (January 1988 – June 2015) of HCHO total columns from ground-based high-resolution Fourier transform infrared (FTIR) solar spectra recorded at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.), allowing for the characterization of the mid-latitudinal atmosphere for background conditions. First we investigate the HCHO diurnal variation, peaking around noontime and mainly driven by the intra-day insolation modulation and methane (CH4) oxidation. We also characterize quantitatively the diurnal cycles by adjusting a parametric model to the observations, which links the daytime to the HCHO columns according to the monthly intra-day regimes. It is then employed to scale all the individual FTIR measurements on a given daytime in order to remove the effect of the intra-day modulation for improving the trend determination and the comparison with HCHO columns simulated by the state-of-the-art chemical transport model GEOS-Chem v9-02. Such a parametric model will be useful to scale the Jungfraujoch HCHO columns on satellite overpass times in the framework of future calibration/validation efforts of space borne sensors. GEOS-Chem sensitivity tests suggest then that the seasonal and inter-annual HCHO column variations above Jungfraujoch are predominantly led by the atmospheric CH4 oxidation, with a maximum contribution of 25 % from the anthropogenic non-methane volatile organic compound precursors during wintertime. Finally, trend analysis of the so-scaled 27-year FTIR time series reveals a long-term evolution of the HCHO columns in the remote troposphere to be related with the atmospheric CH4 fluctuations and the short-term OH variability: +2.9 %/yr between 1988 and 1995, -3.7 %/yr over 1996-2002 and +0.8/% yr from 2003 onwards.

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See detailStratospheric aerosol - Observations, processes, and impact on climate
Kremser, Stefanie; Thomason, Larry W.; von Hobe, Marc; Hermann, Markus; Deshler, Terry; Timmreck, Claudia; Toohey, Matthew; Stenke, Andrea; Schwarz, Joshua P.; Weigel, Ralf; Fueglistaler, Stephan; Prata, Fred J.; Vernier, Jean-Paul; Schlager, Hans; Barnes, John E.; Antuña-Marrero, Juan-Carlos; Fairlie, Duncan; Palm, Mathias; Mahieu, Emmanuel; Notholt, Justus; Rex, Markus; Bingen, Christine; Vanhellemont, Filip; Bourassa, Adam; Plane, John M. C.; Klocke, Daniel; Carn, Simon A.; Clarisse, Lieven; Trickl, Thomas; Neely, Ryan; James, Alexander D.; Rieger, Landon; Wilson, James C.; Meland, Brian

in Reviews of Geophysics (2016)

Interest in stratospheric aerosol and its role in climate has increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space-based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any non-volcanically driven change, making them difficult to understand. While the role of carbonyl sulfide (OCS) as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide (SO2) emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of non-sulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes.

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See detailRetrieval of HCFC-142b (CH3CClF2) from ground-based high-resolution infrared solar spectra: Atmospheric increase since 1989 and comparison with surface and satellite measurements
Mahieu, Emmanuel; Lejeune, Bernard; Bovy, Benoît; Servais, Christian; Toon, Geoffrey C.; Bernath, Peter F.; Boone, Christopher D.; Walker, Kaley A.; Reimann, Stefan; Vollmer, Martin K.; O’Doherty, Simon

in Journal of Quantitative Spectroscopy and Radiative Transfer (2016)

We have developed an approach for retrieving HCFC-142b (CH3CClF2) from ground-based high-resolution infrared solar spectra, using its ν7 band Q branch in the 900–906 cm-1 interval. Interferences by HNO3, CO2 and H2O have to be accounted for. Application of this approach to observations recorded within the framework of long-term monitoring activities carried out at the northern mid-latitude, high-altitude Jungfraujoch station in Switzerland (46.5°N, 8.0°E, 3580 m above sea level) has provided a total column times series spanning the 1989 to mid-2015 time period. A fit to the HCFC-142b daily mean total column time series shows a statistically-significant long-term trend of (1.23±0.08×1013 molec cm-2) per year from 2000 to 2010, at the 2-σ confidence level. This corresponds to a significant atmospheric accumulation of (0.94±0.06) ppt (1 ppt=10-12) per year for the mean tropospheric mixing ratio, at the 2−σ confidence level. Over the subsequent time period (2010–2014), we note a significant slowing down in the HCFC-142b buildup. Our ground-based FTIR (Fourier Transform Infrared) results are compared with relevant data sets derived from surface in situ measurements at the Mace Head and Jungfraujoch sites of the AGAGE (Advanced Global Atmospheric Gases Experiment) network and from occultation measurements by the ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) instrument on-board the SCISAT satellite.

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See detailTowards understanding the variability in biospheric CO2 fluxes: using FTIR spectrometry and a chemical transport model to investigate the sources and sinks of carbonyl sulfide and its link to CO2
Wang, Y.; Deutscher, N. M.; Palm, M.; Warneke, T.; Notholt, J.; Baker, I.; Berry, J.; Suntharalingam, P.; Jones, N.; Mahieu, Emmanuel; Lejeune, Bernard; Hannigan, J.; Conway, S.; Mendonca, J.; Strong, K.; Campbell, J. E.; Wolf, A.; Kremser, S.

in Atmospheric Chemistry and Physics (2016), 16

Understanding carbon dioxide (CO2) biospheric processes is of great importance because the terrestrial exchange drives the seasonal and interannual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake) and respiration (production). Carbonyl sulfide (OCS) could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential means to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR) spectrometry allows for the retrievals of the atmospheric concentrations of both CO2 and OCS from measured solar absorption spectra. Here, we investigate co-located and quasi-simultaneous FTIR measurements of OCS and CO2 performed at five selected sites located in the Northern Hemisphere. These measurements are compared to simulations of OCS and CO2 using a chemical transport model (GEOS-Chem). The coupled biospheric fluxes of OCS and CO2 from the simple biosphere model (SiB) are used in the study. The CO2 simulation with SiB fluxes agrees with the measurements well, while the OCS simulation reproduced a weaker drawdown than FTIR measurements at selected sites, and a smaller latitudinal gradient in the Northern Hemisphere during growing season when comparing with HIPPO (HIAPER Pole-to-Pole Observations) data spanning both hemispheres. An offset in the timing of the seasonal cycle minimum between SiB simulation and measurements is also seen. Using OCS as a photosynthesis proxy can help to understand how the biospheric processes are reproduced in models and to further understand the carbon cycle in the real world.

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See detailRetrieval of ammonia from ground-based FTIR solar spectra
Dammers, Enrico; Vigouroux, C; Palm, M; Mahieu, Emmanuel; Warneke, T; Smale, D; Langerock, B; Franco, Bruno; Van Damme, M; Schaap, M; Notholt, J; Erisman, J W

in Atmospheric Chemistry and Physics (2015), 15

We present a retrieval method for ammonia (NH3) total columns from ground-based Fourier Transform InfraRed (FTIR) observations. Observations from Bremen (53.10° N, 8.85° E), Lauder (45.04° S, 169.68° E), Reunion (20.9° S, 55.50° E) and Jungfraujoch (46.55° N, 7.98° E) were used to illustrate the capabilities of the method. NH3 mean total columns ranging three orders of magnitude were obtained with higher values at Bremen (mean of 13.47 × 1015 molecules cm-2) to the lower values at Jungfraujoch (mean of 0.18 × 1015 molecules cm-2). In conditions with high surface concentrations of ammonia, as in Bremen, it is possible to retrieve information on the vertical gradient as two layers can be discriminated. The retrieval there is most sensitive to ammonia in the planetary boundary layer, where the trace gas concentration is highest. For conditions with low concentrations only the total column can be retrieved. Combining the systematic and random errors we have a mean total error of 26 % for all spectra measured at Bremen (Number of spectra (N) = 554), 30 % for all spectra from Lauder (N =2412), 25 % for spectra from Reunion (N =1262) and 34 % for spectra measured at Jungfraujoch (N =2702). The error is dominated by the systematic uncertainties in the spectroscopy parameters. Station specific seasonal cycles were found to be consistent with known seasonal cycles of the dominant ammonia sources in the station surroundings. The developed retrieval methodology from FTIR-instruments provides a new way to obtain highly time-resolved measurements of ammonia burdens. FTIR-NH3 observations will be useful for understanding the dynamics of ammonia concentrations in the atmosphere and for satellite and model validation. It will also provide additional information to constrain the global ammonia budget.

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See detailPositive trends in Southern Hemisphere carbonyl sulfide
Kremser, Stefanie; Jones, Nicholas B.; Palm, Mathias; Lejeune, Bernard; Wang, Yuting; Smale, Dan; Deutscher, Nicholas M.

in Geophysical Research Letters (2015), 42

Transport of carbonyl sulfide (OCS) from the troposphere to the stratosphere contributes sulfur to the stratospheric aerosol layer, which reflects incoming short-wave solar radiation, cooling the climate system. Previous analyses of OCS observations have shown no significant trend, suggesting that OCS is unlikely to be a major contributor to the reported increases in stratospheric aerosol loading and indicating a balanced OCS budget. Here we present analyses of ground-based Fourier transform spectrometer measurements of OCS at three Southern Hemisphere sites spanning 34.45°S to 77.80°S. At all three sites statistically significant positive trends are seen from 2001 to 2014 with an observed overall trend in total column OCS at Wollongong of 0.73 ± 0.03%/yr, at Lauder of 0.43 ± 0.02%/yr, and at Arrival Heights of 0.45 ± 0.05%/yr. These observed trends in OCS imply that the OCS budget is not balanced and could contribute to constraints on current estimates of sources and sinks.

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See detailAcetylene (C2H2) and hydrogen cyanide (HCN) from IASI satellite observations: global distributions, validation, and comparison with model
Duflot, V.; Wespes, C.; Clarisse, L.; Hurtmans, D.; Ngadi, Y.; Jones, N.; Paton-Walsh, C.; Hadji-Lazaro, J.; Vigouroux, C.; De Mazière, M.; Metzger, J.-M.; Mahieu, Emmanuel; Servais, Christian; Hase, F.; Schneider, M.; Clerbaux, C.; Coheur, P.-F.

in Atmospheric Chemistry and Physics (2015), 15

We present global distributions of C2H2 and hydrogen cyanide (HCN) total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI) for the years 2008–2010. These distributions are obtained with a fast method allowing to retrieve C2H2 abundance globally with a 5% precision and HCN abundance in the tropical (subtropical) belt with a 10% (25 %) precision. IASI data are compared for validation purposes with ground-based Fourier transform infrared (FTIR) spectrometer measurements at four selected stations. We show that there is an overall agreement between the ground-based and space measurements with correlation coefficients for daily mean measurements ranging from 0.28 to 0.81, depending on the site. Global C2H2 and subtropical HCN abundances retrieved from IASI spectra show the expected seasonality linked to variations in the anthropogenic emissions and seasonal biomass burning activity, as well as exceptional events, and are in good agreement with previous spaceborne studies. Total columns simulated by the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) are compared to the ground-based FTIR measurements at the four selected stations. The model is able to capture the seasonality in the two species in most of the cases, with correlation coefficients for daily mean measurements ranging from 0.50 to 0.86, depending on the site. IASI measurements are also compared to the distributions from MOZART-4. Seasonal cycles observed from satellite data are reasonably well reproduced by the model with correlation coefficients ranging from -0.31 to 0.93 for C2H2 daily means, and from 0.09 to 0.86 for HCN daily means, depending on the considered region. However, the anthropogenic (biomass burning) emissions used in the model seem to be overestimated (underestimated), and a negative global mean bias of 1% (16 %) of the model relative to the satellite observations was found for C2H2 (HCN).

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See detailPast changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends
Harris, N. R. P.; Hassler, B.; Tummon, F.; Bodeker, G. E.; Hubert, D.; Petropavlovskikh, I.; Steinbrecht, W.; Anderson, J.; Bhartia, P. K.; Boone, C. D.; Bourassa, A.; Davis, S. M.; Degenstein, D.; Delcloo, A.; Frith, S. M.; Froidevaux, L.; Godin-Beekmann, S.; Jones, N.; Kurylo, M. J.; Kyrölä, E.; Laine, M.; Leblanc, S. T.; Lambert, J.-C.; Liley, B.; Mahieu, Emmanuel; Maycock, A.; De Mazière, M.; Parrish, A.; Querel, R.; Rosenlof, K. H.; Roth, C.; Sioris, C.; Staehelin, J.; Stolarski, R. S.; Stübi, R.; Tamminen, J.; Vigouroux, C.; Walker, K.A.; Wang, H. J.; Wild, J.; Zawodny, J. M.

in Atmospheric Chemistry and Physics (2015), 15(17), 9965--9982

Trends in the vertical distribution of ozone are reported and compared for a number of new and recently revised data sets. The amount of ozone-depleting compounds in the stratosphere (as measured by equivalent effective stratospheric chlorine – EESC) was maximised in the second half of the 1990s. We examine the periods before and after the peak to see if any change in trend is discernible in the ozone record that might be attributable to a change in the EESC trend, though no attribution is attempted. Prior to 1998, trends in the upper stratosphere (~45 km, 4 hPa) are found to be -5 to -10% per decade at mid-latitudes and closer to -5% per decade in the tropics. No trends are found in the mid-stratosphere (28 km, 30 hPa). Negative trends are seen in the lower stratosphere at mid-latitudes in both hemispheres and in the deep tropics. However, it is hard to be categorical about the trends in the lower stratosphere for three reasons: (i) there are fewer measurements, (ii) the data quality is poorer, and (iii) the measurements in the 1990s are perturbed by aerosols from the Mt Pinatubo eruption in 1991. These findings are similar to those reported previously even though the measurements for the main satellite and groundbased records have been revised. There is no sign of a continued negative trend in the upper stratosphere since 1998: instead there is a hint of an average positive trend of ~2% per decade in mid-latitudes and ~3% per decade in the tropics. The significance of these upward trends is investigated using different assumptions of the independence of the trend estimates found from different data sets. The averaged upward trends are significant if the trends derived from various data sets are assumed to be independent (as in Pawson et al., 2014) but are generally not significant if the trends are not independent. This occurs because many of the underlying measurement records are used in more than one merged data set. At this point it is not possible to say which assumption is best. Including an estimate of the drift of the overall ozone observing system decreases the significance of the trends. The significance will become clearer as (i) more years are added to the observational record, (ii) further improvements are made to the historic ozone record (e.g. through algorithm development), and (iii) the data merging techniques are refined, particularly through a more rigorous treatment of uncertainties.

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See detailValidation of SCIAMACHY HDO/H2O measurements using the TCCON and NDACC-MUSICA networks
Scheepmaker, R. A.; Frankenberg, C.; Deutscher, N. M.; Schneider, M.; Barthlott, S.; Blumenstock, T.; Garcia, O. E.; Hase, F.; Jones, N.; Mahieu, Emmanuel; Notholt, J.; Velazco, V.; Landgraf, J.; Aben, I.

in Atmospheric Measurement Techniques (2015), 8(4), 1799-1818

Measurements of the atmospheric HDO/H2O ratio help us to better understand the hydrological cycle and improve models to correctly simulate tropospheric humidity and therefore climate change. We present an updated version of the column-averaged HDO/H2O ratio data set from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The data set is extended with 2 additional years, now covering 2003–2007, and is validated against co-located ground-based total column δD measurements from Fourier transform spectrometers (FTS) of the Total Carbon Column Observing Network (TCCON) and the Network for the Detection of Atmospheric Composition Change (NDACC, produced within the framework of the MUSICA project). Even though the time overlap among the available data is not yet ideal, we determined a mean negative bias in SCIAMACHY δD of −35 ± 30‰ compared to TCCON and −69 ± 15‰ compared to MUSICA (the uncertainty indicating the station-to-station standard deviation). The bias shows a latitudinal dependency, being largest (∼ −60 to −80‰) at the highest latitudes and smallest (∼ −20 to −30‰) at the lowest latitudes. We have tested the impact of an offset correction to the SCIAMACHY HDO and H2O columns. This correction leads to a humidity- and latitude-dependent shift in δD and an improvement of the bias by 27‰, although it does not lead to an improved correlation with the FTS measurements nor to a strong reduction of the latitudinal dependency of the bias. The correction might be an improvement for dry, high-altitude areas, such as the Tibetan Plateau and the Andes region. For these areas, however, validation is currently impossible due to a lack of ground stations. The mean standard deviation of single-sounding SCIAMACHY–FTS differences is ∼ 115‰, which is reduced by a factor ∼ 2 when we consider monthly means. When we relax the strict matching of individual measurements and focus on the mean seasonalities using all available FTS data, we find that the correlation coefficients between SCIAMACHY and the FTS networks improve from 0.2 to 0.7–0.8. Certain ground stations show a clear asymmetry in δD during the transition from the dry to the wet season and back, which is also detected by SCIAMACHY. This asymmetry points to a transition in the source region temperature or location of the water vapour and shows the added information that HDO/H2O measurements provide when used in combination with variations in humidity.

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See detailRetrievals of formaldehyde from ground-based FTIR and MAX-DOAS observations at the Jungfraujoch station and comparisons with GEOS-Chem and IMAGES model simulations
Franco, Bruno; Hendrick, François; Van Roozendael, Michel; Müller, Jean-François; Stavrakou, Trisevgeni; Marais, Eloise; Bovy, Benoît; Bader, Whitney; Fayt, Caroline; Hermans, Christian; Lejeune, Bernard; Pinardi, Gaia; Servais, Christian; Mahieu, Emmanuel

in Atmospheric Measurement Techniques (2015), 8

As an ubiquitous product of the oxidation of many volatile organic compounds (VOCs), formaldehyde (HCHO) plays a key role as a short-lived and reactive intermediate in the atmospheric photo-oxidation pathways leading to the formation of tropospheric ozone and secondary organic aerosols. In this study, HCHO profiles have been successfully retrieved from ground-based Fourier transform infrared (FTIR) solar spectra and UV-visible Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) scans recorded during the July 2010–December 2012 time period at the Jungfraujoch station (Swiss Alps, 46.5° N, 8.0° E, 3580m a.s.l.). Analysis of the retrieved products has revealed different vertical sensitivity between both remote sensing techniques. Furthermore, HCHO amounts simulated by two state-of-the-art chemical transport models (CTMs), GEOSChem and IMAGES v2, have been compared to FTIR total columns and MAX-DOAS 3.6–8 km partial columns, accounting for the respective vertical resolution of each ground-based instrument. Using the CTM outputs as the intermediate, FTIR and MAX-DOAS retrievals have shown consistent seasonal modulations of HCHO throughout the investigated period, characterized by summertime maximum and wintertime minimum. Such comparisons have also highlighted that FTIR and MAX-DOAS provide complementary products for the HCHO retrieval above the Jungfraujoch station. Finally, tests have revealed that the updated IR parameters from the HITRAN 2012 database have a cumulative effect and significantly decrease the retrieved HCHO columns with respect to the use of the HITRAN 2008 compilation.

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See detailImproved spectral fitting of nitrogen dioxide from OMI in the 405-465 nm window
van Geffen, J H G M; Boersma, K F; Van Roozendael, M; Hendrick, F; Mahieu, Emmanuel; De Smedt, I; Sneep, M; Veefkind, J P

in Atmospheric Measurement Techniques (2015), 8

An improved nitrogen dioxide (NO2) slant column density retrieval for the Ozone Monitoring Instrument (OMI) in the 405–465 nm spectral region is presented. Since the launch of OMI on board NASA’s EOS-Aura satellite in 2004, differential optical absorption spectroscopy (DOAS) retrievals of NO2 slant column densities have been the starting point for the KNMI DOMINO and NASA SP NO2 vertical column data as well as the OMI NO2 data of some other institutes. However, recent intercomparisons between NO2 retrievals from OMI and other UV/Vis and limb spectrometers, as well as ground-based measurements, suggest that OMI stratospheric NO2 is biased high. This study revises and, for the first time, fully documents the OMI NO2 retrieval in detail. The representation of the OMI slit function to convolve high-resolution reference spectra onto the relevant spectral grid is improved. The window used for the wavelength calibration is optimised, leading to much-reduced fitting errors. Ozone and water vapour spectra used in the fit are updated, reflecting the recently improved knowledge of their absorption cross section in the literature. The improved spectral fit also accounts for absorption by the O2–O2 collision complex and by liquid water over clearwater areas. The main changes in the improved spectral fitting result from the updates related to the wavelength calibration: the RMS error of the fit is reduced by 23% and the NO2 slant column by 0.85 1015 molec cm-2, independent of latitude, solar zenith angle and NO2 value. Including O2–O2 and liquid water absorption and updating the O3 and water vapour cross-section spectra further reduces NO2 slant columns on average by 0.35 1015 molec cm-2, accompanied by a further 9% reduction in the RMS error of the fit. The improved OMI NO2 slant columns are consistent with independent NO2 retrievals from other instruments to within a range that can be explained by photochemically driven diurnal increases in stratospheric NO2 and by small differences in fitting window and approach. The revisions indicate that current OMI NO2 slant columns suffered mostly from an additive positive offset, which is removed by the improved wavelength calibration and representation of the OMI slit function. It is therefore anticipated that the improved NO2 slant columns are most important to retrievals of spatially homogeneous stratospheric NO2 rather than to heterogeneous tropospheric NO2.

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See detailRetrieval of ethane from ground-based FTIR solar spectra using improved spectroscopy: recent burden increase above Jungfraujoch
Franco, Bruno; Bader, Whitney; Toon, G. C.; Bray, C.; Perrin, A.; Fischer, E. V.; Sudo, K.; Boone, C. D.; Bovy, Benoît; Lejeune, Bernard; Servais, Christian; Mahieu, Emmanuel

in Journal of Quantitative Spectroscopy and Radiative Transfer (2015), 160(C), 36-49

An improved spectroscopy is used to implement and optimize the retrieval strategy of ethane (C2H6) from ground-based Fourier Transform Infrared (FTIR) solar spectra recorded at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5° N, 8.0° E, 3580m a.s.l.). The improved spectroscopic parameters include C2H6 pseudo-lines in the 2720-3100 cm-1 range and updated line parameters for methyl chloride and ozone. These improved spectroscopic parameters allow for substantial reduction of the fitting residuals as well as enhanced information content. They also contribute to limiting oscillations responsible for ungeophysical negative mixing ratio profiles. This strategy has been successfully applied to the Jungfraujoch solar spectra available from 1994 onwards. The resulting time series is compared with C2H6 total columns simulated by the state-of-the-art chemical transport model GEOS-Chem. Despite very consistent seasonal cycles between both data sets, a negative systematic bias relative to the FTIR observations suggests that C2H6 emissions are underestimated in the current inventories implemented in GEOS-Chem. Finally, C2H6 trends are derived from the FTIR time series, revealing a statistically-significant sharp increase of the C2H6 burden in the remote atmosphere above Jungfraujoch since 2009. Evaluating cause of this change in the C2H6 burden, which may be related to the recent massive growth of shale gas exploitation in North America, is of primary importance for atmospheric composition and air quality in the Northern Hemisphere.

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See detailUsing XCO2 retrievals for assessing the long-term consistency of NDACC/FTIR data sets
Barthlott, S; Schneider, M; Hase, F; Wiegele, A; Christner, E; Gonzalez, Y; Blumenstock, T; Dohe, S; Garcia, O E; Sepulveda, E; Strong, K; Mendonca, J; Weaver, D; Palm, M; Deutscher, N M; Warneke, T; Notholt, J; Lejeune, Bernard; Mahieu, Emmanuel; Jones, N; Griffith, D W T; Velazco, V A; Smale, D; Robinson, J; Kivi, R; Heikkinen, P; Raffalski, U

in Atmospheric Measurement Techniques (2015), 8

Within the NDACC (Network for the Detection of Atmospheric Composition Change), more than 20 FTIR (Fourier-transform infrared) spectrometers, spread worldwide, provide long-term data records of many atmospheric trace gases. We present a method that uses measured and modelled XCO2 for assessing the consistency of these NDACC data records. Our XCO2 retrieval setup is kept simple so that it can easily be adopted for any NDACC/FTIR-like measurement made since the late 1950s. By a comparison to coincident TCCON (Total Carbon Column Observing Network) measurements, we empirically demonstrate the useful quality of this suggested NDACC XCO2 product (empirically obtained scatter between TCCON and NDACC is about 4‰ for daily mean as well as monthly mean comparisons, and the bias is 25 ‰). Our XCO2 model is a simple regression model fitted to CarbonTracker results and the Mauna Loa CO2 in situ records. A comparison to TCCON data suggests an uncertainty of the model for monthly mean data of below 3 ‰. We apply the method to the NDACC/FTIR spectra that are used within the project MUSICA (multi-platform remote sensing of isotopologues for investigating the cycle of atmospheric water) and demonstrate that there is a good consistency for these globally representative set of spectra measured since 1996: the scatter between the modelled and measured XCO2 on a yearly time scale is only 3 ‰.

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See detailTrends of ozone total columns and vertical distribution from FTIR observations at eight NDACC stations around the globe
Vigouroux, C; Blumenstock, T; Coffey, M; Errera, Q; Garcia, O; Jones, N B; Hannigan, J W; Hase, F; Liley, B; Mahieu, Emmanuel; Mellqvist, J; Notholt, J; Palm, M; Persson, G; Schneider, M; Servais, Christian; Smale, D; Thölix, L; De Mazière, M

in Atmospheric Chemistry and Physics (2015), 15

Ground-based Fourier transform infrared (FTIR) measurements of solar absorption spectra can provide ozone total columns with a precision of 2 % but also independent partial column amounts in about four vertical layers, one in the troposphere and three in the stratosphere up to about 45 km, with a precision of 5–6 %. We use eight of the Network for the Detection of Atmospheric Composition Change (NDACC) stations having a long-term time series of FTIR ozone measurements to study the total and vertical ozone trends and variability, namely, Ny-Ålesund (79ºN), Thule (77ºN), Kiruna (68ºN), Harestua (60ºN), Jungfraujoch (47ºN), Izaña (28ºN), Wollongong (34ºS) and Lauder (45ºS). The length of the FTIR time series varies by station but is typically from about 1995 to present. We applied to the monthly means of the ozone total and four partial columns a stepwise multiple regression model including the following proxies: solar cycle, quasi-biennial oscillation (QBO), El Niño–Southern Oscillation (ENSO), Arctic and Antarctic Oscillation (AO/AAO), tropopause pressure (TP), equivalent latitude (EL), Eliassen–Palm flux (EPF), and volume of polar stratospheric clouds (VPSC). At the Arctic stations, the trends are found mostly negative in the troposphere and lower stratosphere, very mixed in the middle stratosphere, positive in the upper stratosphere due to a large increase in the 1995–2003 period, and non-significant when considering the total columns. The trends for mid-latitude and subtropical stations are all non-significant, except at Lauder in the troposphere and upper stratosphere and at Wollongong for the total columns and the lower and middle stratospheric columns where they are found positive. At Jungfraujoch, the upper stratospheric trend is close to significance (+0.9 ± 1.0 %/decade). Therefore, some signs of the onset of ozone mid-latitude recovery are observed only in the Southern Hemisphere, while a few more years seem to be needed to observe it at the northern mid-latitude station.

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See detailUpdate on Ozone-Depleting Substances (ODSs) and Other Gases of Interest to the Montreal Protocol
Carpenter, L. J.; Reimann, S.; Burkholder, J. B.; Clerbaux, C.; Hall, B. D.; Hossaini, R.; Laube, J. C.; Yvon-Lewis, S. A.; Engel, A.; Montzka, S. A.; Blake, D. R.; Dorf, M.; Dutton, G. S.; Fraser, P. J.; Froidevaux, L.; Hendrick, F.; Hu, J.; Jones, A.; Krummel, P. B.; Kuijpers, L. J. M.; Kurylo, M. J.; Liang, Q.; Mahieu, Emmanuel; Mühle, J.; O'Doherty, S.; Ohnishi, K.; Orkin, V. L.; Pfeilsticker, K.; Rigby, M.; Simpson, I. J.; Yokouchi, Y.

in Nohende Ajavon, Ayité-Lô; Newman, Paul. A.; Pyle, John A.; Ravishankara, A. R. (Eds.) Scientific Assessment of Ozone Depletion: 2014 (2014)

The amended and adjusted Montreal Protocol has continued to reduce emissions and atmospheric abundances of most controlled ozone-depleting substances. By 2012, the total combined abundance of anthropogenic ODSs in the troposphere (measured as Equivalent Chlorine) had decreased by nearly 10% from its peak value in 1994.

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See detailLong-term evolution and seasonal modulation of methanol above Jungfraujoch (46.5°N, 8.0°E): Optimisation of the retrieval strategy, comparison with model and independant observations
Bader, Whitney; Stavrakou, T; Muller, J-F; Reimann, S; Boone, C.D.; Harrison, J.J.; Flock, Olivier; Bovy, Benoît; Franco, Bruno; Lejeune, Bernard; Servais, Christian; Mahieu, Emmanuel

in Atmospheric Measurement Techniques (2014), 7

Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5° N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected υ8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995–2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June–July, minimum columns in winter and a peak-to-peak amplitude of 130%. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations.

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See detailRecent Northern Hemisphere stratospheric HCl increase due to atmospheric circulation changes
Mahieu, Emmanuel; Chipperfield, M. P.; Notholt, J.; Reddmann, T.; Anderson, J.; Bernath, P. F.; Blumenstock, T.; Coffey, M. T.; Dhomse, S. S.; Feng, W.; Franco, Bruno; Froidevaux, L.; Griffith, D. W. T.; Hannigan, J. W.; Hase, F.; Hossaini, R.; Jones, N. B.; Morino, I.; Murata, I.; Nakajima, H.; Palm, M.; Paton-Walsh, C.; Russell III, J. M.; Schneider, M.; Servais, Christian; Smale, D.; Walker, K. A.

in Nature (2014), 515(7525), 104--107

The abundance of chlorine in the Earth’s atmosphere increased considerably during the 1970s to 1990s, following large emissions of anthropogenic long-lived chlorine-containing source gases, notably the chlorofluorocarbons. The chemical inertness of chlorofluorocarbons allows their transport and mixing throughout the troposphere on a global scale[1], before they reach the stratosphere where they release chlorine atoms that cause ozone depletion[2]. The large ozone loss over Antarctica[3] was the key observation that stimulated the definition and signing in 1987 of the Montreal Protocol, an international treaty establishing a schedule to reduce the production of the major chlorine- and bromine-containing halocarbons. Owing to its implementation, the near-surface total chlorine concentration showed a maximum in 1993, followed by a decrease of half a per cent to one per cent per year[4], in line with expectations. Remote-sensing data have revealed a peak in stratospheric chlorine after 1996[5], then a decrease of close to one per cent per year[6,7], in agreement with the surface observations of the chlorine source gases and model calculations[7]. Here we present ground-based and satellite data that show a recent and significant increase, at the 2σ level, in hydrogen chloride (HCl), the main stratospheric chlorine reservoir, starting around 2007 in the lower stratosphere of the Northern Hemisphere, in contrast with the ongoing monotonic decrease of near-surface source gases. Using model simulations, we attribute this trend anomaly to a slowdown in the Northern Hemisphere atmospheric circulation, occurring over several consecutive years, transporting more aged air to the lower stratosphere, and characterized by a larger relative conversion of source gases to HCl. This short-term dynamical variability will also affect other stratospheric tracers and needs to be accounted for when studying the evolution of the stratospheric ozone layer.

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See detailSelf-broadening coefficients and improved line intensities for the ν7 band of ethylene near 10.5 μm, and impact on ethylene retrievals from Jungfraujoch solar spectra
Vander Auwera, Jean; Fayt, A; Tudorie, M; Rotger, M; Boudon, V; Franco, Bruno; Mahieu, Emmanuel

in Journal of Quantitative Spectroscopy and Radiative Transfer (2014), 148

Relying on high-resolution Fourier transform infrared (FTIR) spectra, the present work involved extensive measurements of individual line intensities and self broadening coefficients for the nu7 band of 12C2H4. The measured self broadening coefficients exhibit a dependence on both J and Ka. Compared to the corresponding information available in the latest edition of the HITRAN spectroscopic database, the measured line intensities were found to be higher by about 10 % for high J lines in the P branch and lower by about 5 % for high J lines of the R branch, varying between these two limits roughly linearly with the line positions. The impact of the presently measured line intensities on retrievals of atmospheric ethylene in the 949.0-952.0 cm-1 microwindow was evaluated using a subset of ground-based high-resolution FTIR solar spectra recorded at the Jungfraujoch station. The use of HITRAN 2012 with line intensities modified to match the present measurements led to a systematic reduction of the measured total columns of ethylene by -4.1+/-0.1 %.

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See detailSpectrometric monitoring of atmospheric carbon tetrafluoride (CF4) above the Jungfraujoch station since 1989: evidence of continued increase but at a slowing rate
Mahieu, Emmanuel; Zander, Rodolphe; Toon, G. C.; Vollmer, M. K.; Reimann, S.; Mühle, J.; Bader, Whitney; Bovy, Benoît; Lejeune, Bernard; Servais, Christian; Demoulin, Philippe; Roland, G.; Bernath, P. F.; Boone, C. D.; Walker, K. A.; Duchatelet, P.

in Atmospheric Measurement Techniques (2014), 7

The long-term evolution of the vertical column abundance of carbon tetrafluoride (CF4) above the high-altitude Jungfraujoch station (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.) has been derived from the spectrometric analysis of Fourier transform infrared solar spectra recorded at that site between 1989 and 2012. The investigation is based on a multi-microwindow approach, two encompassing pairs of absorption lines belonging to the R-branch of the strong ν3 band of CF4 centered at 1283 cm−1, and two additional ones to optimally account for weak but overlapping HNO3 interferences. The analysis reveals a steady accumulation of the very long-lived CF4 above the Jungfraujoch at mean rates of (1.38 ± 0.11) × 1013 molec cm−2 yr−1 from 1989 to 1997, and (0.98 ± 0.02) × 1013 molec cm−2 yr−1 from 1998 to 2012, which correspond to linear growth rates of 1.71 ± 0.14 and 1.04 ± 0.02% yr−1 respectively referenced to 1989 and 1998. Related global CF4 anthropogenic emissions required to sustain these mean increases correspond to 15.8 ± 1.3 and 11.1 ± 0.2 Gg yr−1 over the above specified time intervals. Findings reported here are compared and discussed with respect to relevant northern mid-latitude results obtained remotely from space and balloons as well as in situ at the ground, including new gas chromatography mass spectrometry measurements performed at the Jungfraujoch since 2010.

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See detailMeasurements of hydrogen cyanide (HCN) and acetylene (C2H2) from the Infrared Atmospheric Sounding Interferometer (IASI)
Duflot, V.; Hurtmans, D.; Clarisse, L.; R'honi, Y.; Vigouroux, C.; De Mazière, M.; Mahieu, Emmanuel; Servais, Christian; Clerbaux, C.; Coheur, P.-F.

in Atmospheric Measurement Techniques (2013), 6

Hydrogen cyanide (HCN) and acetylene (C2H2) are ubiquitous atmospheric trace gases with medium lifetime, which are frequently used as indicators of combustion sources and as tracers for atmospheric transport and chemistry. Because of their weak infrared absorption, overlapped by the CO2 Q branch near 720 cm−1, nadir sounders have up to now failed to measure these gases routinely. Taking into account CO2 line mixing, we provide for the first time extensive measurements of HCN and C2H2 total columns at Reunion Island (21° S, 55° E) and Jungfraujoch (46° N, 8° E) in 2009–2010 using observations from the Infrared Atmospheric Sounding Interferometer (IASI). A first order comparison with local ground-based Fourier transform InfraRed (FTIR) measurements has been carried out allowing tests of seasonal consistency which is reasonably captured, except for HCN at Jungfraujoch. The IASI data shows a greater tendency to high C2H2 values. We also examine a nonspecific biomass burning plume over austral Africa and show that the emission ratios with respect to CO agree with previously reported values.

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See detailRecent trend anomaly of hydrogen chloride (HCl) at northern mid-latitudes derived from Jungfraujoch, HALOE and ACE-FTS Infrared solar observations
Mahieu, Emmanuel; Zander, Rodolphe; Bernath, Peter F.; Boone, Christopher D.; Walker, Kaley A.

in Bernath, Peter F. (Ed.) The Atmospheric Chemistry Experiment ACE at 10: A Solar Occultation Anthology (2013)

In this contribution, we analyze infrared solar observations recorded from the ground at the Jungfraujoch station and from space with the HALOE and the ACE-FTS instruments to derive time series of stratospheric columns of hydrogen chloride (HCl) at Northern mid-latitudes. We investigate the Jungfraujoch and the composite satellite time series to characterize the evolution of HCl over the last 15 years, i.e. after its peak loading which occurred in 1996 in this region of the Earth’s atmosphere. Trends derived from both data sets are compared and possible causes for the recent change in the stratospheric HCl buildup are evoked.

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See detailGround-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA
Schneider, M.; Barthlott, S.; Hase, F.; González, Y.; Yoshimura, K.; García, O.E.; Sepúlveda, E.; Gomez-Pelaez, A.; Gisi, M.; Kohlhepp, R.; Dohe, S.; Blumenstock, T.; Wiegele, A.; Christner, E.; Strong, K.; Weaver, D.; Palm, M.; Deutscher, N.M.; Warneke, T.; Notholt, J.; Lejeune, Bernard; Demoulin, Philippe; Jones, N.; Griffith, D.W.T.; Smale, D.; Robinson, J.

in Atmospheric Measurement Techniques (2012), 5(2012), 3007-3027

Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change). We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere) to 8 km (in the upper troposphere) and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and the cross-dependence on humidity are the leading error sources. We introduce an a posteriori correction method of the cross-dependence on humidity, and we recommend applying it to isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model). We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle.

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See detailValidation of IASI FORLI carbon monoxide retrievals using FTIR data from NDACC
Kerzenmacher, T; Dils, B; Kumps, N; Blumenstock, T; Clerbaux, C; Coheur, P.-F.; Demoulin, Philippe; Garcia, O; George, M; Griffith, DWT; Hase, F; Hadji-Lazaro, J; Hurtmans, D; Jones, N; Mahieu, Emmanuel; Notholt, J; Paton-Walsh, C; Raffalski, U; Ridder, T; Schneider, M; Servais, Christian; De Mazière, M

in Atmospheric Measurement Techniques (2012), 5

Carbon monoxide (CO) is retrieved daily and globally from space-borne IASI radiance spectra using the Fast Optimal Retrievals on Layers for IASI (FORLI) software developed at the Université Libre de Bruxelles (ULB). The IASI CO total column product for 2008 from the most recent FORLI retrieval version (20100815) is evaluated using correlative CO profile products retrieved from groundbased solar absorption Fourier transform infrared (FTIR) observations at the following FTIR spectrometer sites from the Network for the Detection of Atmospheric Composition Change (NDACC): Ny-Alesund, Kiruna, Bremen, Jungfraujoch, Izana and Wollongong. In order to have good statistics for the comparisons, we included all IASI data from the same day, within a 100 km radius around the ground-based stations. The individual ground-based data were adjusted to the lowest altitude of the co-located IASI CO profiles. To account for the different vertical resolutions and sensitivities of the ground-based and satellite measurements, the averaging kernels associated with the various retrieved products have been used to properly smooth coincident data products. It has been found that the IASI CO total column products compare well on average with the co-located ground-based FTIR total columns at the selected NDACC sites and that there is no significant bias for the mean values at all stations.

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See detailAnalysis of stratospheric NO2 trends above Jungfraujoch using ground-based UV-visible, FTIR, and satellite nadir observations
Hendrick, F; Mahieu, Emmanuel; Bodeker, G E; Boersma, K F; Chipperfield, M P; De Mazière, M; De Smedt, I; Demoulin, Philippe; Fayt, C; Hermans, C; Kreher, K; Lejeune, Bernard; Pinardi, G; Servais, Christian; Stübi, R; van der A, R; Vernier, J-P; Van Roozendael, M

in Atmospheric Chemistry and Physics (2012), 12

The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5°N, 8.0°E) is assessed using ground-based FTIR and zenith-scattered visible sunlight SAOZ measurements over the period 1990 to 2009 as well as a composite satellite nadir data set constructed from ERS-2/GOME, ENVISAT/SCIAMACHY, and METOP-A/GOME-2 observations over the 1996–2009 period. To calculate the trends, a linear least squares regression model including explanatory variables for a linear trend, the mean annual cycle, the quasi-biennial oscillation (QBO), solar activity, and stratospheric aerosol loading is used. For the 1990–2009 period, statistically indistinguishable trends of -3.7±1.1%/decade and -3.6±0.9%/decade are derived for the SAOZ and FTIR NO2 column time series, respectively. SAOZ, FTIR, and satellite nadir data sets show a similar decrease over the 1996–2009 period, with trends of -2.4±1.1%/decade, -4.3±1.4%/decade, and -3.6±2.2%/decade, respectively. The fact that these declines are opposite in sign to the globally observed +2.5%/decade trend in N2O, suggests that factors other than N2O are driving the evolution of stratospheric NO2 at northern mid-latitudes. Possible causes of the decrease in stratospheric NO2 columns have been investigated. The most likely cause is a change in the NO2/NO partitioning in favor of NO, due to a possible stratospheric cooling and a decrease in stratospheric chlorine content, the latter being further confirmed by the negative trend in the ClONO2 column derived from FTIR observations at Jungfraujoch. Decreasing ClO concentrations slows the NO+ ClO -> NO2 + Cl reaction and a stratospheric cooling slows the NO+O3 -> NO2 +O2 reaction, leaving more NOx in the form of NO. The slightly positive trends in ozone estimated from ground- and satellitebased data sets are also consistent with the decrease of NO2 through the NO2 +O3 -> NO3 +O2 reaction. Finally, we cannot rule out the possibility that a strengthening of the Dobson-Brewer circulation, which reduces the time available for N2O photolysis in the stratosphere, could also contribute to the observed decline in stratospheric NO2 above Jungfraujoch.

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See detailObserved and simulated time evolution of HCl, ClONO2, and HF total column abundances
Kohlhepp, R; Ruhnke, R; Chipperfield, M P; De Mazière, M; Notholt, J; Barthlott, S; Batchelor, R L; Blatherwick, R D; Blumenstock, Th; Coffey, M T; Demoulin, Philippe; Fast, H; Feng, W; Goldman, A; Griffith, D W T; Hamann, K; Hannigan, J W; Hase, F; Jones, N B; Kagawa, A; Kaiser, I; Kasai, Y; Kirner, O; Kouker, W; Lindenmaier, R; Mahieu, Emmanuel; Mittermeier, R L; Monge-Sanz, B; Morino, I; Murata, I; Nakajima, H; Palm, M; Paton-Walsh, C; Raffalski, U; Reddmann, Th; Rettinger, M; Rinsland, C P; Rozanov, E; Schneider, M; Senten, C; Servais, Christian; Sinnhuber, B-M; Smale, D; Strong, K; Sussmann, R; Taylor, J R; Vanhaelewyn, G; Warneke, T; Whaley, C; Wiehle, M; Wood, S W

in Atmospheric Chemistry and Physics (2012), 12(7), 3527--3556

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites belonging to the Network for the Detection of Atmospheric Composition Change (NDACC) and located between 80.05°N and 77.82°S. By providing such a near-global overview on ground-based measurements of the two major stratospheric chlorine reservoir species, HCl and ClONO2, the present study is able to confirm the decrease of the atmospheric inorganic chlorine abundance during the last few years. This decrease is expected following the 1987 Montreal Protocol and its amendments and adjustments, where restrictions and a subsequent phase-out of the prominent anthropogenic chlorine source gases (solvents, chlorofluorocarbons) were agreed upon to enable a stabilisation and recovery of the stratospheric ozone layer. The atmospheric fluorine content is expected to be influenced by the Montreal Protocol, too, because most of the banned anthropogenic gases also represent important fluorine sources. But many of the substitutes to the banned gases also contain fluorine so that the HF total column abundance is expected to have continued to increase during the last few years. The measurements are compared with calculations from five different models: the two-dimensional Bremen model, the two chemistry-transport models KASIMA and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. Thereby, the ability of the models to reproduce the absolute total column amounts, the seasonal cycles, and the temporal evolution found in the FTIR measurements is investigated and inter-compared. This is especially interesting because the models have different architectures. The overall agreement between the measurements and models for the total column abundances and the seasonal cycles is good. Linear trends of HCl, ClONO2, and HF are calculated from both measurement and model time series data, with a focus on the time range 2000–2009. This period is chosen because from most of the measurement sites taking part in this study, data are available during these years. The precision of the trends is estimated with the bootstrap resampling method. The sensitivity of the trend results with respect to the fitting function, the time of year chosen and time series length is investigated, as well as a bias due to the irregular sampling of the measurements. The measurements and model results investigated here agree qualitatively on a decrease of the chlorine species by around 1%yr-1. The models simulate an increase of HF of around 1%yr-1. This also agrees well with most of the measurements, but some of the FTIR series in the Northern Hemisphere show a stabilisation or even a decrease in the last few years. In general, for all three gases, the measured trends vary more strongly with latitude and hemisphere than the modelled trends. Relative to the FTIR measurements, the models tend to underestimate the decreasing chlorine trends and to overestimate the fluorine increase in the Northern Hemisphere. At most sites, the models simulate a stronger decrease of ClONO2 than of HCl. In the FTIR measurements, this difference between the trends of HCl and ClONO2 depends strongly on latitude, especially in the Northern Hemisphere.

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See detailProcess-evaluation of tropospheric humidity simulated by general circulation models using water vapor isotopologues: 1. Comparison between models and observations
Risi, C; Noone, D; Worden, J; Frankenberg, C; Stiller, G; Kiefer, M; Funke, B; Walker, K A; Bernath, P F; Schneider, M; Wunch, D; Sherlock, V; Deutscher, N; Griffith, D; Wennberg, P O; Strong, K; Smale, D; Mahieu, Emmanuel; Barthlott, S; Hase, F; Garcia, O; Notholt, J; Warneke, T; Toon, G C; Sayres, D; Bony, S; Lee, J; Brown, D; Uemura, R; Sturm, C

in Journal of Geophysical Research (2012), 117(D5), 05303

N2 - The goal of this study is to determine how H2O and HDO measurements in water vapor can be used to detect and diagnose biases in the representation of processes controlling tropospheric humidity in atmospheric general circulation models (GCMs). We analyze a large number of isotopic data sets (four satellite, sixteen ground-based remote-sensing, five surface in situ and three aircraft data sets) that are sensitive to different altitudes throughout the free troposphere. Despite significant differences between data sets, we identify some observed HDO/H2O characteristics that are robust across data sets and that can be used to evaluate models. We evaluate the isotopic GCM LMDZ, accounting for the effects of spatiotemporal sampling and instrument sensitivity. We find that LMDZ reproduces the spatial patterns in the lower and mid troposphere remarkably well. However, it underestimates the amplitude of seasonal variations in isotopic composition at all levels in the subtropics and in midlatitudes, and this bias is consistent across all data sets. LMDZ also underestimates the observed meridional isotopic gradient and the contrast between dry and convective tropical regions compared to satellite data sets. Comparison with six other isotope-enabled GCMs from the SWING2 project shows that biases exhibited by LMDZ are common to all models. The SWING2 GCMs show a very large spread in isotopic behavior that is not obviously related to that of humidity, suggesting water vapor isotopic measurements could be used to expose model shortcomings. In a companion paper, the isotopic differences between models are interpreted in terms of biases in the representation of processes controlling humidity.

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See detailDecrease of the Carbon Tetrachloride (CCl4) Loading above Jungfraujoch, based on High Resolution Infrared Solar Spectra recorded between 1999 and 2011
Rinsland, C. P.; Mahieu, Emmanuel; Demoulin, Philippe; Zander, Rodolphe; Servais, Christian; Hartmann, J.-M.

in Journal of Quantitative Spectroscopy and Radiative Transfer (2012), 113

The long-term trend of the atmospheric carbon tetrachloride (CCl4) burden has been retrieved from high spectral resolution infrared solar absorption spectra recorded between January 1999 and June 2011. The observations were made with a Fourier transform spectrometer at the northern mid-latitude, high altitude Jungfraujoch station in Switzerland (46.5°N latitude, 8.0°E longitude, 3580 m altitude). Total columns were derived from spectrometric analysis of the strong CCl4 ν3 band at 794 cm-1, accounting for all interfering molecules (e.g., H2O, CO2, O3, and a dozen weakly absorbing gases). A significant improvement in the fitting residuals and in the retrieved CCl4 columns was obtained by taking into account line mixing in a strong interfering CO2 Q branch. This procedure had never been implemented in remote sensing CCl4 retrievals though its importance was noted in earlier studies. A fit to the CCl4 daily mean total column time series returns a statistically-significant long-term trend of (-1.49±0.08 x 1013 molec./cm2)/yr, 2-σ. This corresponds to an annual decrease of (-1.31±0.07) pptv for the mean free tropospheric volume mixing ratio. Furthermore, the total column data set reveals a weak seasonal cycle with a peak-to-peak amplitude of 4.5 %, with minimum and maximum values occurring in mid-February and mid-September, respectively. This small seasonal modulation is attributed primarily to the residual influence of tropopause height changes throughout the year. The negative trend of the CCl4 loading reflects the continued impact of the regulations implemented by the Montreal Protocol and its strengthening amendments and adjustments. Despite this statistically significant decrease, the CCl4 molecule currently remains an important contributor to the atmospheric chlorine budget, and thus deserves further monitoring, to ensure continued compliance with these strengthenings, globally. Our present findings are briefly discussed with respect to recent relevant CCl4 investigations at the ground and from space.

See detailFourier Transform Infrared Spectrometry
Schneider, Matthias; Demoulin, Philippe; Sussmann, Ralf; Notholt, Justus

in Kämpfer, Niklaus (Ed.) Monitoring Atmospheric Water Vapour : Ground-Based Remote Sensing and In-situ Methods (2012)

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See detailCarbon monoxide (CO) and ethane (C2H6) trends from ground-based solar FTIR measurements at six European stations, comparison and sensitivity analysis with the EMEP model
Angelbratt, J.; Mellqvist, J.; Simpson, D.; Jonson, J. E.; Blumenstock, T.; Borsdorff, T.; Duchatelet, Pierre; Forster, F.; Hase, F.; Mahieu, Emmanuel; De Mazière, M.; Notholt, J.; Petersen, A. K.; Raffalski, U.; Servais, Christian; Sussmann, R.; Warneke, T.; Vigouroux, C.

in Atmospheric Chemistry and Physics (2011), 11(17), 9253--9269

Trends in the CO and C2H6 partial columns ~0–15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996–2006 time period. The CO trends from the four stations Jungfraujoch, Zugspitze, Harestua and Kiruna have been estimated to −0.45 ± 0.16% yr−1, −1.00 ± 0.24% yr−1, −0.62 ± 0.19 % yr−1 and −0.61 ± 0.16% yr−1, respectively. The corresponding trends for C2H6 are −1.51 ± 0.23% yr−1, −2.11 ± 0.30% yr−1, −1.09 ± 0.25% yr−1 and −1.14 ± 0.18% yr−1. All trends are presented with their 2-σ confidence intervals. To find possible reasons for the CO trends, the global-scale EMEP MSC-W chemical transport model has been used in a series of sensitivity scenarios. It is shown that the trends are consistent with the combination of a 20% decrease in the anthropogenic CO emissions seen in Europe and North America during the 1996–2006 period and a 20% increase in the anthropogenic CO emissions in East Asia, during the same time period. The possible impacts of CH4 and biogenic volatile organic compounds (BVOCs) are also considered. The European and global-scale EMEP models have been evaluated against the measured CO and C2H6 partial columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and Ny-Ålesund. The European model reproduces, on average the measurements at the different sites fairly well and within 10–22% deviation for CO and 14–31% deviation for C2H6. Their seasonal amplitude is captured within 6–35% and 9–124% for CO and C2H6, respectively. However, 61–98% of the CO and C2H6 partial columns in the European model are shown to arise from the boundary conditions, making the global-scale model a more suitable alternative when modeling these two species. In the evaluation of the global model the average partial columns for 2006 are shown to be within 1–9% and 37–50% of the measurements for CO and C2H6, respectively. The global model sensitivity for assumptions made in this paper is also analyzed.

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See detailA new method to detect long term trends of methane (CH4) and nitrous oxide (N2O) total columns measured within the NDACC ground-based high resolution solar FTIR network
Angelbratt, J.; Mellqvist, J.; Blumenstock, T.; Borsdorff, T.; Brohede, S.; Duchatelet, Pierre; Forster, F.; Hase, F.; Mahieu, Emmanuel; Murtagh, D.; Petersen, A. K.; Schneider, M.; Sussmann, R.; Urban, J.

in Atmospheric Chemistry and Physics (2011), 11(13), 6167--6183

Total columns measured with the ground-based solar FTIR technique are highly variable in time due to atmospheric chemistry and dynamics in the atmosphere above the measurement station. In this paper, a multiple regression model with anomalies of air pressure, total columns of hydrogen fluoride (HF) and carbon monoxide (CO) and tropopause height are used to reduce the variability in the methane (CH4) and nitrous oxide (N2O) total columns to estimate reliable linear trends with as small uncertainties as possible. The method is developed at the Harestua station (60 N, 11 E, 600m a.s.l.) and used on three other European FTIR stations, i.e. Jungfraujoch (47 N, 8 E, 3600m a.s.l.), Zugspitze (47 N, 11 E, 3000m a.s.l.), and Kiruna (68 N, 20 E, 400m a.s.l.). Linear CH4 trends between 0.13±0.01-0.25±0.02%yr-1 were estimated for all stations in the 1996-2009 period. A piecewise model with three separate linear trends, connected at change points, was used to estimate the short term fluctuations in the CH4 total columns. This model shows a growth in 1996–1999 followed by a period of steady state until 2007. From 2007 until 2009 the atmospheric CH4 amount increases between 0.57±0.22–1.15±0.17%yr-1. Linear N2O trends between 0.19±0.01–0.40±0.02%yr-1 were estimated for all stations in the 1996-2007 period, here with the strongest trend at Harestua and Kiruna and the lowest at the Alp stations. From the N2O total columns crude tropospheric and stratospheric partial columns were derived, indicating that the observed difference in the N2O trends between the FTIR sites is of stratospheric origin. This agrees well with the N2O measurements by the SMR instrument onboard the Odin satellite showing the highest trends at Harestua, 0.98±0.28%yr-1, and considerably smaller trends at lower latitudes, 0.27±0.25%yr-1. The multiple regression model was compared with two other trend methods, the ordinary linear regression and a Bootstrap algorithm. The multiple regression model estimated CH4 and N2O trends that differed up to 31% compared to the other two methods and had uncertainties that were up to 300% lower. Since the multiple regression method were carefully validated this stresses the importance to account for variability in the total columns when estimating trend from solar FTIR data.

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See detail1997–2007 CO trend at the high Alpine site Jungfraujoch: a comparison between NDIR surface in situ and FTIR remote sensing observations
Dils, B.; Cui, J.; Henne, S.; Mahieu, Emmanuel; Steinbacher, M.; De Mazière, M.

in Atmospheric Chemistry and Physics (2011), 11(13), 6735--6748

Within the atmospheric research community, there is a strong interest in integrated datasets, combining data from several instrumentations. This integration is complicated by the different characteristics of the datasets, inherent to the measurement techniques. Here we have compared two carbon monoxide time series (1997 till 2007) acquired at the high-Alpine research station Jungfraujoch (3580 m above sea level), with two well-established measurement techniques, namely in situ surface concentration measurements using Non-Dispersive Infrared Absorption technology (NDIR), and ground-based remote sensing measurements using solar absorption Fourier Transform Infrared spectrometry (FTIR). The profile information available in the FTIR signal allowed us to extract an independent layer with a top height of 7.18 km above sea level, appropriate for comparison with our in situ measurements. We show that, even if both techniques are able to measure free troposphere CO concentrations, the datasets exhibit marked differences in their overall trends (−3.21 ± 0.03 ppb/year for NDIR vs. −0.8 ± 0.4 ppb/year for FTIR). Removing measurements that are polluted by uprising boundary layer air has a strong impact on the NDIR trend (now −2.62 ± 0.03 ppb/year), but its difference with FTIR remains significant. Using the LAGRANTO trajectory model, we show that both measurement techniques are influenced by different source regions and therefore are likely subject to exhibit significant differences in their overall trend behaviour. However the observation that the NDIR-FTIR trend difference is as significant before as after 2001 is at odds with available emission databases which claim a significant Asian CO increase after 2001 only.

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See detailFormic acid above the Jungfraujoch during 1985–2007: observed variability, seasonality, but no long-term background evolution
Zander, Rodolphe; Duchatelet, Pierre; Mahieu, Emmanuel; Demoulin, Philippe; Roland, Ginette; Servais, Christian; Auwera, J. V.; Perrin, A.; Rinsland, C. P.; Crutzen, P. J.

in Atmospheric Chemistry and Physics (2010), 10(20), 10047--10065

This paper reports on daytime total vertical column abundances of formic acid (HCOOH) above the Northern mid-latitude, high altitude Jungfraujoch station (Switzerland; 46.5° N, 8.0° E, 3580 m alt.). The columns were derived from the analysis of infrared solar observations regularly performed with high spectral resolution Fourier transform spectrometers during over 1500 days between September 1985 and September 2007. The investigation was based on the spectrometric fitting of five spectral intervals, one encompassing the HCOOH ν6 band Q branch at 1105 cm−1, and four additional ones allowing to optimally account for critical temperature-sensitive or time-evolving interferences by other atmospheric gases, in particular HDO, CCl2F2 and CHClF2. The main results derived from the 22 years long database indicate that the free tropospheric burden of HCOOH above the Jungfraujoch undergoes important short-term daytime variability, diurnal and seasonal modulations, inter-annual anomalies, but no significant long-term background change. A major progress in the remote determination of the atmospheric HCOOH columns reported here has resulted from the adoption of new, improved absolute spectral line intensities for the infrared ν6 band of trans-formic acid, resulting in retrieved free tropospheric loadings being about a factor two smaller than if derived with previous spectroscopic parameters. Implications of this significant change with regard to earlier remote measurements of atmospheric formic acid and comparison with relevant Northern mid-latitude findings, both in situ and remote, will be assessed critically. Sparse HCOOH model predictions will also be evoked and assessed with respect to findings reported here.

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See detailHydrogen fluoride total and partial column time series above the Jungfraujoch from long-term FTIR measurements: Impact of the line-shape model, characterization of the error budget and seasonal cycle, and comparison with satellite and model data
Duchatelet, Pierre; Demoulin, Philippe; Hase, Frank; Ruhnke, Roland; Feng, Wuhu; Chipperfield, Martyn; Bernath, Peter; Boone, Chris; Walker, Kaley; Mahieu, Emmanuel

in Journal of Geophysical Research. Atmospheres (2010), 115

Time series of hydrogen fluoride (HF) total columns have been derived from ground-based Fourier transform infrared (FTIR) solar spectra recorded between March 1984 and December 2009 at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m asl) with two high resolution spectrometers (one home-made and one Bruker 120-HR). Solar spectra have been inverted with the PROFFIT 9.5 algorithm, using the optimal estimation method. An inter-comparison of HF total columns retrieved with PROFFIT and SFIT-2 – the other reference algorithm in the FTIR community - is performed for the first time. The effect of a Galatry line shape model on HF retrieved total columns and vertical profiles, on the residuals of the fits and on the error budget is also quantified. Information content analysis indicates that, in addition to HF total vertical abundance, three independent stratospheric HF partial columns can be derived from our Bruker spectra. A complete error budget has been established and indicates that the main source of systematic error is linked to HF spectroscopy and that the random error affecting our HF total columns does not exceed 2.5%. Ground-based middle and upper stratospheric HF amounts have been compared to satellite data collected by the HALOE or ACE-FTS instruments. Comparisons of our FTIR HF total and partial columns with runs performed by two 3D numerical models (SLIMCAT and KASIMA) are also included. Finally, FTIR and model HF total and partial columns time series have been analyzed to derive the main characteristics of their seasonal cycles.

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See detailValidation of five years (2003–2007) of SCIAMACHY CO total column measurements using ground-based spectrometer observations
de Laat, A. T. J.; Gloudemans, A. M. S.; Schrijver, H.; Aben, I.; Nagahama, Y.; Suzuki, K.; Mahieu, Emmanuel; Jones, N. B.; Paton-Walsh, C.; Deutscher, N. M.; Griffith, D. W. T.; De Mazière, M.; Mittermeier, R. L.; Fast, H.; Notholt, J.; Palm, M.; Hawat, T.; Blumenstock, T.; Hase, F.; Schneider, M.; Rinsland, C. P.; Dzhola, A. V.; Grechko, E. I.; Poberovskii, A. M.; Makarova, M. V.; Mellqvist, J.; Strandberg, A.; Sussmann, R.; Borsdorff, T.; Rettinger, M.

in Atmospheric Measurement Techniques (2010), 3(5), 1457--1471

This paper presents a validation study of SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum Likelihood Method (IMLM) algorithm using ground-based spectrometer observations from twenty surface stations for the five year time period of 2003–2007. Overall we find a good agreement between SCIAMACHY and ground-based observations for both mean values as well as seasonal variations. For high-latitude Northern Hemisphere stations absolute differences between SCIAMACHY and ground-based measurements are close to or fall within the SCIAMACHY CO 2σ precision of 0.2 × 1018 molecules/cm2 (~10%) indicating that SCIAMACHY can observe CO accurately at high Northern Hemisphere latitudes. For Northern Hemisphere mid-latitude stations the validation is complicated due to the vicinity of emission sources for almost all stations, leading to higher ground-based measurements compared to SCIAMACHY CO within its typical sampling area of 8° × 8°. Comparisons with Northern Hemisphere mountain stations are hampered by elevation effects. After accounting for these effects, the validation provides satisfactory results. At Southern Hemisphere mid- to high latitudes SCIAMACHY is systematically lower than the ground-based measurements for 2003 and 2004, but for 2005 and later years the differences between SCIAMACHY and ground-based measurements fall within the SCIAMACHY precision. The 2003–2004 bias is consistent with previously reported results although its origin remains under investigation. No other systematic spatial or temporal biases could be identified based on the validation presented in this paper. Validation results are robust with regard to the choices of the instrument-noise error filter, sampling area, and time averaging required for the validation of SCIAMACHY CO total column measurements. Finally, our results show that the spatial coverage of the ground-based measurements available for the validation of the 2003–2007 SCIAMACHY CO columns is sub-optimal for validation purposes, and that the recent and ongoing expansion of the ground-based network by carefully selecting new locations may be very beneficial for SCIAMACHY CO and other satellite trace gas measurements validation efforts.

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See detailAn approach to retrieve information on the carbonyl fluoride (COF2) vertical distributions above Jungfraujoch by FTIR multi-spectrum multi-window fitting
Duchatelet, Pierre; Mahieu, Emmanuel; Ruhnke, Roland; Feng, Wuhu; Chipperfield, Martyn; Demoulin, Philippe; Bernath, Peter; Boone, Chris; Walker, Kaley; Servais, Christian; Flock, Olivier

in Atmospheric Chemistry and Physics (2009), 9

We present an original multi-spectrum fitting procedure to retrieve volume mixing ratio (VMR) profiles of carbonyl fluoride (COF2) from ground-based high resolution Fourier transform infrared (FTIR) solar spectra. The multi-spectrum approach consists of simultaneously combining, during the retrievals, all spectra recorded consecutively during the same day and with the same resolution. Solar observations analyzed in this study with the SFIT-2 v3.91 fitting algorithm correspond to more than 2900 spectra recorded between January 2000 and December 2007 at high zenith angles, with a Fourier Transform Spectrometer operated at the high-altitude International Scientific Station of the Jungfraujoch (ISSJ, 46.5° N latitude, 8.0° E longitude, 3580 m altitude), Switzerland. The goal of the retrieval strategy described here is to provide information about the vertical distribution of carbonyl fluoride. The microwindows used are located in the ν4 or in the ν4 COF2 infrared (IR) absorption bands. Averaging kernel and eigenvector analysis indicates that our FTIR retrieval is sensitive to COF2 inversion between 17 and 30 km, with the major contribution to the retrieved information always coming from the measurement. Moreover, there was no significant bias between COF2 partial columns, total columns or VMR profiles retrieved from the two bands. For each wavenumber region, a complete error budget including all identified sources has been carefully established. In addition, comparisons of FTIR COF2 17–30 km partial columns with KASIMA and SLIMCAT 3-D CTMs are also presented. If we do not notice any significant bias between FTIR and SLIMCAT time series, KASIMA COF2 17–30 km partial columns are lower of around 25%, probably due to incorrect lower boundary conditions. For each times series, linear trend estimation for the 2000–2007 time period as well as a seasonal variation study are also performed and critically discussed. For FTIR and KASIMA time series, very low COF2 growth rates (0.4±0.2%/year and 0.3±0.2%/year, respectively) have been derived. However, the SLIMCAT data set gives a slight negative trend (−0.5±0.2%/year), probably ascribable to discontinuities in the meteorological data used by this model. We further demonstrate that all time series are able to reproduce the COF2 seasonal cycle, which main seasonal characteristics deduced from each data set agree quite well.

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See detailTechnical Note: Harmonized retrieval of column-integrated atmospheric water vapor from the FTIR network - First examples for long-term records and station trends
Sussmann, R.; Borsdorff, T.; Rettinger, M.; Camy-Peyret, C.; Demoulin, Philippe; Duchatelet, Pierre; Mahieu, Emmanuel; Servais, Christian

in Atmospheric Chemistry and Physics (2009), 9(22), 8987-8999

We present a method for harmonized retrieval of integrated water vapor (IWV) from existing, long-term, measurement records at the ground-based mid-infrared solar FTIR spectrometry stations of the Network for the Detection of Atmospheric Composition Change (NDACC). Correlation of IWV from FTIR with radiosondes shows an ideal slope of 1.00(3). This optimum matching is achieved via tuning one FTIR retrieval parameter, i.e., the strength of a Tikhonov regularization constraining the derivative (with respect to height) of retrieved water profiles given in per cent difference relative to an a priori profile. All other FTIR-sonde correlation parameters (intercept = 0.02(12) mm, bias = 0.02(5) mm, standard deviation of coincident IWV differences (stdv) = 0.27 mm, R = 0.99) are comparable to or better than results for all other ground-based IWV sounding techniques given in the literature. An FTIR-FTIR side-by-side intercomparison reveals a strong exponential increase in stdv as a function of increasing temporal mismatch starting at Δt ≈ 1 minute. This is due to atmospheric water vapor variability. Based on this result we derive an upper limit for the precision of the FTIR IWV retrieval for the smallest Δt (= 3.75 min) still giving a statistically sufficient sample (32 coincidences), i.e., precision (IWVFTIR) < 0.05 mm (or 2.2 % of the mean IWV). The bias of the IWV retrievals from the two different FTIR instruments is nearly negligible (0.02(1) mm). The optimized FTIR IWV retrieval is set up in the standard NDACC algorithm SFIT 2 without changes to the code. A concept for harmonized transfer of the retrieval between different stations deals with all relevant control parameters; it includes correction for differing spectral point spacings (via regularization strength), and final quality selection of the retrievals (excluding the highest residuals (measurement minus model), 5% of the total). As first application examples long-term IWV data sets are retrieved from the FTIR records of the Zugspitze (47.4 °N, 11.0 °E, 2964 m a.s.l.) and Jungfraujoch (46.5 °N, 8.0 °E, 3580 m a.s.l.) NDACC sites. Station-trend analysis comprises a linear fit after subtracting an intra-annual model (3 Fourier components) and constructing an uncertainty interval [95 % confidence] via bootstrap resampling. For the Zugspitze a significant trend of 0.79 [0.65, 0.92] mm/decade is found for the time interval [1996 - 2008], whereas for the Jungfraujoch no significant trend is found. This confirms recent findings that strong variations of IWV trends do occur above land on the local to regional scale (≈250 km) in spite of homogeneous surface temperature trends. This paper provides a basis for future exploitation of more than a dozen existing, multi-decadal FTIR measurement records around the globe for climate studies.

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See detailTrend of lower stratospheric methane (CH4) from Atmospheric Chemistry Experiment (ACE) and Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements
Rinsland, Curtis P.; Chiou, Linda S.; Boone, C. D.; Bernath, P. F.; Mahieu, Emmanuel; Zander, Rodolphe

in Journal of Quantitative Spectroscopy and Radiative Transfer (2009), 110(13), 1066-1071

The long-term trend of methane (CH4) in the lower stratosphere has been estimated for the 1985 to 2008 time period by combining spaceborne solar occultation measurements recorded with high spectral resolution Fourier transform spectrometers (FTSs). Volume mixing ratio (VMR) FTS measurements from the ATMOS (Atmospheric Trace Molecule Spectroscopy) FTS covering 120-10 hPa (~16 to 30 km altitude) at 25°N-35°N latitude from 1985 and 1994 have been combined with Atmospheric Chemistry Experiment (ACE) SCISAT-1 FTS measurements covering the same latitude and pressure range from 2004 to 2008. The CH4 trend was estimated by referencing the VMRs to those measured for the long-lived constituent N2O to account for the dynamic history of the sampled airmasses. The combined measurement set shows that the VMR increase measured by ATMOS has been replaced by a leveling off during the ACE measurement time period. Our conclusion is consistent with both remote sensing and in situ measurements of the CH4 trend obtained over the same time span.

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See detailAn FPGA-Based Data Acquisition and Processing System for the MATMOS FTIR Instrument.
Bekker, Dmitriy L; Blavier, Jean-Francois L.; Toon, Geoffrey C; Servais, Christian

in IEEE Aerospace Conference Proceedings (2009), (1233), 11

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See detailFirst ground-based infrared solar absorption measurements of free tropospheric methanol (CH3OH): Multidecade infrared time series from Kitt Peak (31.9°N 111.6°W), trend, seasonal cycle, and comparison with previous measurements
Rinsland, Curtis P.; Mahieu, Emmanuel; Chiou, Linda; Herbin, Hervé

in Journal of Geophysical Research (2009), 114(D04309),

Atmospheric CH3OH (methanol) free tropospheric (2.09-14 km altitude) time series spanning 22 years has been analyzed based on high spectral resolution infrared solar absorption spectra of the strong ν8 band recorded from the U.S. National Solar Observatory on Kitt Peak (latitude 31.9°N, 111.6°W, 2.09 km altitude) with a 1-m Fourier transform spectrometer (FTS). The measurements span October 1981 to December 2003 and are the first long time series of CH3OH measurements obtained from the ground. The results were analyzed with SFIT2 version 3.93 and show a factor of three variations with season, a maximum at the beginning of July, a winter minimum, and no statistically significant long-term trend over the measurement time span.

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See detailValidation of version-4.61 methane and nitrous oxide observed by MIPAS
Payan, S.; Camy-Peyret, C.; Oelhaf, H.; Wetzel, G.; Maucher, G.; Keim, C.; Pirre, M.; Huret, N.; Engel, A.; Volk, M. C.; Kuellmann, H.; Kuttippurath, J.; Cortesi, U.; Bianchini, G.; Mencaraglia, F.; Raspollini, P.; Redaelli, G.; Vigouroux, C.; De Maziere, M.; Mikuteit, S.; Blumenstock, Thomas; Velazco, V.; Notholt, J.; Mahieu, Emmanuel; Duchatelet, Pierre; Smale, D.; Wood, S.; Jones, N.; Piccolo, C.; Payne, V.; Bracher, A.; Glatthor, N.; Stiller, G.; Grunow, K.; Jeseck, P.; Te, Y.; Butz, A.

in Atmospheric Chemistry and Physics (2009), 9(2), 413-442

The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-borne, aircraft, satellite and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign or ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH4 and N2O profiles produced by the current ESA operational software (Instrument Processing Facility version 4.61 or IPF v4.61, full resolution MIPAS data covering the period 9 July 2002 to 26 March 2004) and correlative measurements obtained from balloon and aircraft experiments as well as from satellite sensors or from ground-based instruments. In the middle stratosphere, no significant bias is observed between MIPAS and correlative measurements, and MIPAS is providing a very consistent and global picture of the distribution of CH4 and N2O in this region. In average, the MIPAS CH4 values show a small positive bias in the lower stratosphere of about 5%. A similar situation is observed for N2O with a positive bias of 4%. In the lower stratosphere/upper troposphere (UT/LS) the individual used MIPAS data version 4.61 still exhibits some unphysical oscillations in individual CH4 and N2O profiles caused by the processing algorithm (with almost no regularization). Taking these problems into account, the MIPAS CH4 and N2O profiles are behaving as expected from the internal error estimation of IPF v4.61 and the estimated errors of the correlative measurements.

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See detailFirst measurements of the HCFC-142b trend from atmospheric chemistry experiment (ACE) solar occultation spectra
Rinsland, Curtis P; Chiou, Linda; Boone, Chris; Bernath, Peter; Mahieu, Emmanuel

in Journal of Quantitative Spectroscopy and Radiative Transfer (2009), 110(18), 2127-2134

The first measurement of the HCFC-142b (CH3CClF2) trend near the tropopause has been derived from volume mixing ratio (VMR) measurements at northern and southern hemisphere mid-latitudes for the 2004-2008 time period from spaceborne solar occultation observations recorded at 0.02 cm(-1) resolution with the ACE (atmospheric chemistry experiment) Fourier transform spectrometer. The HCFC-142b molecule is currently the third most abundant HCFC (hydrochlorofluorocarbon) in the atmosphere and ACE measurements over this time span show a continuous rise in its volume mixing ratio. Monthly average measurements at northern and southern hemisphere mid-latitudes have similar increase rates that are consistent with surface trend measurements for a similar time span. A mean northern hemisphere profile for the time span shows a near constant VMR at 8-20 km altitude range, consistent on average for the same time span with in situ results. The nearly constant vertical VMR profile also agrees with model predictions of a long lifetime in the lower atmosphere. (c) 2009 Elsevier Ltd. All rights reserved.

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See detailWhat drives the observed variability of HCN in the troposphere and lower stratosphere?
Li, Q.; Palmer, P. I.; Pumphrey, H. C.; Bernath, P.; Mahieu, Emmanuel

in Atmospheric Chemistry and Physics (2009), 9(21), 8531-8543

We use the GEOS-Chem global 3-D chemistry transport model to investigate the relative importance of chemical and physical processes that determine observed variability of hydrogen cyanide (HCN) in the troposphere and lower stratosphere. Consequently, we reconcile ground-based FTIR column measurements of HCN, which show annual and semi-annual variations, with recent space-borne measurements of HCN mixing ratio in the tropical lower stratosphere, which show a large two-year variation. We find that the observed column variability over the ground-based stations is determined by a superposition of HCN from several regional burning sources, with GEOS-Chem reproducing these column data with a positive bias of 5%. GEOS-Chem reproduces the observed HCN mixing ratio from the Microwave Limb Sounder and the Atmospheric Chemistry Experiment satellite instruments with a mean negative bias of 20%, and the observed HCN variability with a mean negative bias of 7%. We show that tropical biomass burning emissions explain most of the observed HCN variations in the upper troposphere and lower stratosphere (UTLS), with the remainder due to atmospheric transport and HCN chemistry. In the mid and upper stratosphere, atmospheric dynamics progressively exerts more influence on HCN variations. The extent of temporal overlap between African and other continental burning seasons is key in establishing the apparent bienniel cycle in the UTLS. Similar analysis of other, shorter-lived trace gases have not observed the transition between annual and bienniel cycles in the UTLS probably because the signal of inter-annual variations from surface emission has been diluted before arriving at the lower stratosphere (LS), due to shorter atmospheric lifetimes.

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See detailValidation of ozone measurements from the Atmospheric Chemistry Experiment (ACE)
Dupuy, Eric; Walker, K. A.; Kar, J.; Boone, C. D.; McElroy, C. T.; Bernath, P. F.; Drummond, J. R.; Skelton, R.; McLeod, S. D.; Hughes, R. C.; Nowlan, C. R.; Burrows, J. P.; Catoire, V.; Ceccherini, S.; Chabrillat, S.; Christensen, T.; Coffey, M. T.; Cortesi, U.; Davies, J.; Degenstein, D. A.; Maziere, M. De; Demoulin, Philippe; De Clercq, C.; Dodion, J.; Firanski, B.; Fischer, H.; Forbes, G.; Froidevaux, L.; Fussen, D.; Gérard, P.; Goutail, F.; Granville, J.; Griffith, D.; Godin-Beekmann, S.; Haley, C. S.; Hannigan, J. W.; Hoepfner, M.; Jin, J. J.; Jones, A.; Jones, N. B.; Jucks, K.; Kasai, Y.; Kerzenmacher, T. E.; Kleinboehl, A.; Kagawa, A.; Klekociuk, A. R.; Kramer, I.; Kuellmann, H.; Kuttippurath, J.; Kyroelae, E.; Lambert, J.-C.; Livesey, N. J.; Lloyd, N. D.; Mahieu, Emmanuel; Manney, Gloria L.; Llewellyn, E. J.; Marshall, B. T.; McConnell, J. C.; McCormick, M. P.; McDermid, I. S.; McHugh, M.; McLinden, C. A.; Mellqvist, J.; Murayama, Y.; Murtagh, D. P.; Oelhaf, H.; Mizutani, K.; Parrish, A.; Petelina, S. V.; Piccolo, C.; Pommereau, J. P.; Randall, C. E.; Robert, C.; Roth, C.; Senten, C.; Steck, T.; Strandberg, A.; Schneider, M.; Strawbridge, K. B.; Sussmann, R.; Swart, D. P. J.; Tarasick, D. W.; Taylor, J. R.; Tetard, C.; Thomason, L. W.; Tully, M. B.; Urban, J.; Vanhellemont, F.; Thompson, A. M.; Vigouroux, C.; von Clarmann, T.; von der Gathen, P.; von Savigny, C.; Waters, J. W.; Witte, J. C.; Wolff, M.; Dufour, G.; Zou, J.; Nichitiu, F.; Zawodny, J. M.; Strong, K.; Baron, P.; Bevilacqua, Richard M.; Blumenstock, T.; Bodeker, G. E.; Borsdorff, T.; Bourassa, A. E.; Bovensmann, H.; Bracher, A.; Brogniez, C.; Boyd, I. S.

in Atmospheric Chemistry and Physics (2009), 9(2), 287-343

This paper presents extensive bias determination analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from nearly 20 satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the average values of the mean relative differences are nearly all within +1 to +8%. At higher altitudes (45 60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments, with mean relative differences of up to +40% (about + 20% on average). For the ACE-MAESTRO version 1.2 ozone data product, mean relative differences are within +/- 10% (average values within +/- 6%) between 18 and 40 km for both the sunrise and sunset measurements. At higher altitudes (similar to 35-55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (with mean relative differences down to -10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS, indicating a large positive bias (mean relative differences within +10 to +30%) in the 45-55 km altitude range. In contrast, there is no significant systematic difference in bias found for the ACE-FTS sunrise and sunset measurements.

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See detailTrend analysis of greenhouse gases over Europe measured by a network of ground-based remote FTIR instruments
Gardiner, Tom; Forbes, A.; De Mazière, Martine; Vigouroux, Corinne; Mahieu, Emmanuel; Demoulin, Philippe; Velazco, Voltaire; Notholt, Justus; Blumenstock, Thomas; Hase, Frank; Kramer, Isabell; Sussmann, Ralf; Stremme, Wolfgang; Mellqvist, Johan; Strandberg, Anders; Ellingsen, Kjerstin; Gauss, Michael

in Atmospheric Chemistry and Physics (2008), 8(22), 6719-6727

This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European network of ground-based solar FTIR instruments to determine the trends in the tropospheric, stratospheric and total columns of ozone, nitrous oxide, carbon monoxide, methane, ethane and HCFC-22. The suitability of the method has been demonstrated through statistical validation of the technique, and comparison with ground-based in-situ measurements and 3-D atmospheric models.

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See detailMeasurements of long-term changes in atmospheric OCS (carbonyl sulfide) from infrared solar observations
Rinsland, Curtis P.; Chiou, Linda S.; Mahieu, Emmanuel; Zander, Rodolphe; Boone, Christopher D.; Bernath, Peter

in Journal of Quantitative Spectroscopy and Radiative Transfer (2008), 109(16), 2679-2686

Multi-decade atmospheric OCS (carbonyl sulfide) infrared measurements have been analyzed with the goal of quantifying long-term changes and evaluating the consistency of the infrared atmospheric OCS remote-sensing measurement record. Solar-viewing grating spectrometer measurements recorded in April 1951 at the Jungfraujoch station (46.5°N latitude, 8.0°E longitude, 3.58 km altitude) show evidence for absorption by lines of the strong ν3 band of OCS at 2062 cm(−1). The observation predates the earliest previously reported OCS atmosphere remote-sensing measurement by two decades. More recent infrared ground-based measurements of OCS have been obtained primarily with high-resolution solar-viewing Fourier transform spectrometers (FTSs). Long-term trends derived from this record span more than two decades and show OCS columns that have remained constant or have decreased slightly with time since the Mt. Pinatubo eruption, though retrievals assuming different versions of public spectroscopic databases have been impacted by OCS ν3 band line intensity differences of 10%. The lower stratospheric OCS trend has been inferred assuming spectroscopic parameters from the high-resolution transmission (HITRAN) 2004 database. Volume mixing ratio (VMR) profiles measured near 30°N latitude with high-resolution solar-viewing FTSs operating in the solar occultation mode over a 22 years time span were combined. Atmospheric Trace MOlecucle Spectroscopy (ATMOS) version 3 FTS measurements in 1985 and 1994 were used with Atmospheric Chemistry Experiment (ACE) measurements during 2004–2007. Trends were calculated by referencing the measured OCS VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled airmasses. Means and 1-sigma standard deviations of VMRs (in ppbv, or 10−9 per unit air volume) averaged over 30–100 hPa from measurements at 25–35°N latitude are 0.334±0.089 ppbv from 1985 (ATMOS Spacelab 3 measurements), 0.297±0.094 ppbv from 1994 ATLAS 3 measurements, 0.326±0.074 ppbv from ACE 2004 measurements, 0.305±0.096 ppbv from ACE 2005 measurements, 0.328±0.074 from ACE 2006 measurements, and 0.305±0.090 ppbv from ACE measurements through August 2007. Assuming these parameters, we conclude that there has been no statistically significant trend in lower stratospheric OCS over the measurement time span. We discuss past measurement sets, quantify the impact of changes in infrared spectroscopic parameters on atmospheric retrievals and trend measurements, and discuss OCS spectroscopic uncertainties of the current ν3 band parameters in public atmospheric databases.

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See detailValidation of ACE-FTS v2.2 measurements of HCl, HF, CCl3F and CCl2F2 using space-, balloon- and ground-based instrument observations
Mahieu, Emmanuel; Duchatelet, Pierre; Demoulin, Philippe; Walker, Kaley; Dupuy, Eric; Froidevaux, Lucien; Randall, Cora; Catoire, Valéry; Strong, Kimberley; Boone, Christopher D.; Bernath, Peter; Blavier, Jean-François; Blumenstock, Thomas; Coffey, Mike; De Mazière, Martine; Griffith, Dave; Hannigan, Jim; Hase, Franck; Jones, Nicholas; Jucks, Ken; Kagawa, Akiko; Kasai, Yasuko; Mebarki, Y.; Mikuteit, Sabine; Nassar, Ray; Notholt, Justus; Rinsland, Curtis P.; Robert, C.; Schrems, O.; Senten, Cindy; Smale, Dan; Taylor, Jeffrey R.; Tétard, C.; Toon, Geoffrey C.; Warneke, Thorsten; Wood, Stephen W.; Zander, Rodolphe; Servais, Christian

in Atmospheric Chemistry and Physics (2008), 8

Hydrogen chloride (HCl) and hydrogen fluoride (HF) are respectively the main chlorine and fluorine reservoirs in the Earth's stratosphere. Their buildup resulted from the intensive use of man-made halogenated source gases, in particular CFC-11 (CCl3F) and CFC-12 (CCl2F2), during the second half of the 20th century. It is important to continue monitoring the evolution of these source gases and reservoirs, in support of the Montreal Protocol and also indirectly of the Kyoto Protocol. The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) is a space-based instrument that has been performing regular solar occultation measurements of over 30 atmospheric gases since early 2004. In this validation paper, the HCl, HF, CFC-11 and CFC-12 version 2.2 profile data products retrieved from ACE-FTS measurements are evaluated. Volume mixing ratio profiles have been compared to observations made from space by MLS and HALOE, and from stratospheric balloons by SPIRALE, FIRS-2 and Mark-IV. Partial columns derived from the ACE-FTS data were also compared to column measurements from ground-based Fourier transform instruments operated at 12 sites. ACE-FTS data recorded from March 2004 to August 2007 have been used for the comparisons. These data are representative of a variety of atmospheric and chemical situations, with sounded air masses extending from the winter vortex to summer sub-tropical conditions. Typically, the ACE-FTS products are available in the 10-50 km altitude range for HCl and HF, and in the 7-20 and 7-25 km ranges for CFC-11 and -12, respectively. For both reservoirs, comparison results indicate an agreement generally better than 5-10% above 20 km altitude, when accounting for the known offset affecting HALOE measurements of HCl and HF. Larger positive differences are however found for comparisons with single profiles from FIRS-2 and SPIRALE. For CFCs, the few coincident measurements available suggest that the differences probably remain within +/-20%.

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See detailValidation of ACE-FTS N2O measurements
Strong, Kimberley; Wolff, Mareile A; Kerzenmacher, Tobias E; Walker, Kaley A.; Bernath, Peter; Blumenstock, Thomas; Boone, Christopher D.; Catoire, Valéry; Coffey, Michael; De Mazière, Martine; Demoulin, Philippe; Duchatelet, Pierre; Dupuy, Eric; Hannigan, Jim; Hoepfner, Michael; Glatthor, N.; Griffith, Dave W. T.; Jin, J. J.; Jones, Nicholas; Jucks, Ken; Küllmann, Harry; Kuttippurath, Jayan; Lambert, A.; Mahieu, Emmanuel; McConnell, John C.; Mellqvist, Johan; Mikuteit, Sabine; Murtagh, Donal; Notholt, Justus; Piccolo, C.; Raspollini, P.; Ridolfi, M.; Robert, C.; Schneider, Matthias; Schrems, O.; Semeniuk, K.; Senten, Cindy; Stiller, G. P.; Strandberg, Anders; Taylor, Jeffrey R.; Tétard, Cédric; Toohey, M.; Urban, J.; Warneke, Thorsten; Wood, Stephen W.

in Atmospheric Chemistry and Physics (2008), 8(16), 4759-4786

The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, was launched on 12 August 2003, carrying two instruments that measure vertical profiles of atmospheric constituents using the solar occultation technique. One of these instruments, the ACE Fourier Transform Spectrometer (ACE-FTS), is measuring volume mixing ratio (VMR) profiles of nitrous oxide (N2O) from the upper troposphere to the lower mesosphere at a vertical resolution of about 3-4 km. In this study, the quality of the ACE-FTS version 2.2 N2O data is assessed through comparisons with coincident measurements made by other satellite, balloon-borne, aircraft, and ground-based instruments. These consist of vertical profile comparisons with the SMR, MLS, and MIPAS satellite instruments, multiple aircraft flights of ASUR, and single balloon flights of SPIRALE and FIRS-2, and partial column comparisons with a network of ground-based Fourier Transform InfraRed spectrometers (FTIRs). Between 6 and 30 km, the mean absolute differences for the satellite comparisons lie between -42 ppbv and +17 ppbv, with most within +/- 20 ppbv. This corresponds to relative deviations from the mean that are within +/- 15%, except for comparisons with MIPAS near 30 km, for which they are as large as 22.5%. Between 18 and 30 km, the mean absolute differences for the satellite comparisons are generally within +/- 10 ppbv. From 30 to 60 km, the mean absolute differences are within +/- 4 ppbv, and are mostly between -2 and +1 ppbv. Given the small N2O VMR in this region, the relative deviations from the mean are therefore large at these altitudes, with most suggesting a negative bias in the ACE-FTS data between 30 and 50 km. In the comparisons with the FTIRs, the mean relative differences between the ACE-FTS and FTIR partial columns (which cover a mean altitude range of 14 to 27 km) are within +/- 5.6% for eleven of the twelve contributing stations. This mean relative difference is negative at ten stations, suggesting a small negative bias in the ACE-FTS partial columns over the altitude regions compared. Excellent correlation (R=0.964) is observed between the ACE-FTS and FTIR partial columns, with a slope of 1.01 and an intercept of -0.20 on the line fitted to the data.

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See detailValidation of HNO3, ClONO2, and N2O5 from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)
Wolff, Mareile; Kerzenmacher, Tobias; Strong, Kimberley; Walker, Kaley A.; Toohey, M.; Dupuy, Eric; Bernath, Peter; Boone, Christopher D.; Brohede, S.; Catoire, Valéry; von Clarmann, Thomas; Coffey, M.; Daffer, W. H.; De Mazière, Martine; Duchatelet, Pierre; Glatthor, N.; Griffith, Dave W. T.; Hannigan, Jim; Hase, Frank; Hoepfner, Michael; Huret, Nathalie; Jones, Nicholas; Jucks, Ken; Kagawa, Akiko; Kasai, Y.; Kramer, Isabell; Küllmann, Harry; Kuttippurath, Jayan; Mahieu, Emmanuel; Manney, Gloria L.; McElroy, C. T.; McLinden, C.; Mébarki, Y.; Mikuteit, Sabine; Murtagh, Donal; Piccolo, C.; Raspollini, P.; Ridolfi, M.; Ruhnke, Roland; Santee, M.; Senten, Cindy; Smale, Dan; Tétard, Cédric; Urban, J.; Wood, Stephen W.

in Atmospheric Chemistry and Physics (2008), 8(13), 3529-3562

The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra in the ultraviolet/visible and infrared wavelength regions. The reservoir gases HNO3, ClONO2, and N2O5 are three of the key species provided by the primary instrument, the ACE Fourier Transform Spectrometer (ACE-FTS). This paper describes the ACE-FTS version 2.2 data products, including the N2O5 update, for the three species and presents validation comparisons with available observations. We have compared volume mixing ratio (VMR) profiles of HNO3, ClONO2, and N2O5 with measurements by other satellite instruments (SMR, MLS, MIPAS), aircraft measurements (ASUR), and single balloon-flights (SPIRALE, FIRS-2). Partial columns of HNO3 and ClONO2 were also compared with measurements by ground-based Fourier Transform Infrared (FTIR) spectrometers. Overall the quality of the ACE-FTS v2.2 HNO3 VMR profiles is good from 18 to 35 km. For the statistical satellite comparisons, the mean absolute differences are generally within ±1 ppbv ±20%) from 18 to 35 km. For MIPAS and MLS comparisons only, mean relative differences lie within±10% between 10 and 36 km. ACE-FTS HNO3 partial columns (~15–30 km) show a slight negative bias of −1.3% relative to the ground-based FTIRs at latitudes ranging from 77.8° S–76.5° N. Good agreement between ACE-FTS ClONO2 and MIPAS, using the Institut für Meteorologie und Klimaforschung and Instituto de Astrofísica de Andalucía (IMK-IAA) data processor is seen. Mean absolute differences are typically within ±0.01 ppbv between 16 and 27 km and less than +0.09 ppbv between 27 and 34 km. The ClONO2 partial column comparisons show varying degrees of agreement, depending on the location and the quality of the FTIR measurements. Good agreement was found for the comparisons with the midlatitude Jungfraujoch partial columns for which the mean relative difference is 4.7%. ACE-FTS N2O5 has a low bias relative to MIPAS IMK-IAA, reaching −0.25 ppbv at the altitude of the N2O5 maximum (around 30 km). Mean absolute differences at lower altitudes (16–27 km) are typically −0.05 ppbv for MIPAS nighttime and ±0.02 ppbv for MIPAS daytime measurements.

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See detailTechnical Note: New ground-based FTIR measurements at Ile de La Réunion: observations, error analysis, and comparisons with independent data
Senten, Cindy; De Mazière, Martine; Dils, Bart; Hermans, Christian; Kruglanski, Michel; Neefs, E.; Scolas, F.; Vandaele, A. C.; Vanhaelewyn, G.; Vigouroux, Corinne; Carleer, Michel; Coheur, Pierre-François; Fally, Sophie; Barret, Brice; Baray, J. L.; Delmas, R.; Leveau, J.; Metzger, J. M.; Mahieu, Emmanuel; Boone, Christopher D.; Walker, Kaley A.; Bernath, Peter; Strong, Kimberley

in Atmospheric Chemistry and Physics (2008), 8(13), 3483-3508

Ground-based high spectral resolution Fourier-transform infrared (FTIR) solar absorption spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. This work presents results from two FTIR measurement campaigns in 2002 and 2004, held at Ile de La Réunion (21° S, 55° E). These campaigns represent the first FTIR observations carried out at a southern (sub)tropical site. They serve the initiation of regular, long-term FTIR monitoring at this site in the near future. To demonstrate the capabilities of the FTIR measurements at this location for tropospheric and stratospheric monitoring, a detailed report is given on the retrieval strategy, information content and corresponding full error budget evaluation for ozone (O3), methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), ethane (C2H6), hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO3) total and partial column retrievals. Moreover, we have made a thorough comparison of the capabilities at sea level altitude (St.-Denis) and at 2200 m a.s.l. (Maïdo). It is proved that the performances of the technique are such that the atmospheric variability can be observed, at both locations and in distinct altitude layers. Comparisons with literature and with correlative data from ozone sonde and satellite (i.e., ACE-FTS, HALOE and MOPITT) measurements are given to confirm the results. Despite the short time series available at present, we have been able to detect the seasonal variation of CO in the biomass burning season, as well as the impact of particular biomass burning events in Africa and Madagascar on the atmospheric composition above Ile de La Réunion. We also show that differential measurements between St.-Denis and Maïdo provide useful information about the concentrations in the boundary layer.

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See detailCO measurements from the ACE-FTS satellite instrument: data analysis and validation using ground-based, airborne and spaceborne observations
Clerbaux, Catherine; George, Maya; Turquety, Solène; Walker, Kaley A.; Barret, Brice; Bernath, Peter; Boone, Christopher D.; Borsdorff, T.; Cammas, J. P.; Catoire, Valéry; Coffey, M.; Coheur, Pierre-François; Deeter, M.; De Mazière, Martine; Drummond, James; Duchatelet, Pierre; Dupuy, Eric; de Zafra, R.; Eddounia, Fadoua; Edwards, David P.; Emmons, L.; Funke, B.; Gille, J.; Griffith, Dave W. T.; Hannigan, Jim; Hase, Frank; Hoepfner, Michael; Jones, Nicholas; Kagawa, Akiko; Kasai, Y.; Kramer, Isabell; Le Flochmoën, E.; Livesey, N. J.; López-Puertas, M.; Luo, M.; Mahieu, Emmanuel; Murtagh, Donal; Nédélec, P.; Pazmino, A.; Pumphrey, Hugh; Ricaud, P.; Rinsland, Curtis P.; Robert, C.; Schneider, Matthias; Senten, Cindy; Stiller, Gabrielle; Strandberg, Anders; Strong, Kimberley; Sussmann, Ralf; Thouret, Valérie; Urban, J.; Wiacek, Aldona

in Atmospheric Chemistry and Physics (2008), 8

The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS). This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006). We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane) observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES) as well as limb-viewing remote sensors (MIPAS, SMR and MLS) were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above). These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (8–12 km), than 30% in the lower stratosphere (12–30 km), and than 25% from 30 to 100 km.

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See detailValidation of ACE-FTS v2.2 methane profiles from the upper troposphere to the lower mesosphere
De Mazière, Martine; Vigouroux, Corinne; Bernath, Peter; Baron, P.; Blumenstock, Thomas; Boone, Christopher D.; Brogniez, Colette; Catoire, Valéry; Coffey, M.; Duchatelet, Pierre; Griffith, D. W. T.; Hannigan, Jim; Kasai, Y.; Kramer, Isabell; Jones, Nicholas; Mahieu, Emmanuel; Manney, Gloria L.; Piccolo, C.; Randall, Cora; Robert, C.; Senten, Cindy; Strong, Kimberley; Taylor, Jeffrey R.; Tétard, Cédric; Walker, Kaley A.; Wood, Stephen W.

in Atmospheric Chemistry and Physics (2008), 9(9), 2421-2435

The ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) solar occultation instrument that was launched onboard the Canadian SCISAT-1 satellite in August 2003 is measuring vertical profiles from the upper troposphere to the lower mesosphere for a large number of atmospheric constituents. Methane is one of the key species. The version v2.2 data of the ACE-FTS CH4 data have been compared to correlative satellite, balloon-borne and ground-based Fourier transform infrared remote sensing data to assess their quality. The comparison results indicate that the accuracy of the data is within 10% in the upper troposphere – lower stratosphere, and within 25% in the middle and higher stratosphere up to the lower mesosphere (<60 km). The observed differences are generally consistent with reported systematic uncertainties. ACE-FTS is also shown to reproduce the variability of methane in the stratosphere and lower mesosphere.

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See detailMIPAS: an instrument for atmospheric and climate research
Fischer, H.; Birk, M.; Blom, C.; Carli, B.; Carlotti, M.; von Clarmann, T.; Delbouille, L.; Dudhia, A.; Ehhalt, D.; Endemann, M.; Flaud, J. M.; Gessner, R.; Kleinert, A.; Koopman, R.; Langen, J.; López-Puertas, M.; Mosner, P.; Nett, H.; Oelhaf, H.; Perron, G.; Remedios, J.; Ridolfi, M.; Stiller, G.; Zander, Rodolphe

in Atmospheric Chemistry and Physics (2008), 8(8), 2151--2188

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See detailOur Changing Atmosphere: Evidence Based on Long-Term Infrared Solar Observations at the Jungfraujoch since 1950
Zander, Rodolphe; Mahieu, Emmanuel; Demoulin, Philippe; Duchatelet, Pierre; Roland, Ginette; Servais, Christian; De Mazière, Martine; Reimann, Stefan; Rinsland, Curtis P.

in Science of the Total Environment (2008), 391(2-3), 184-95

The Institute of Astrophysics of the University of Liege has been present at the High Altitude Research Station Jungfraujoch, Switzerland, since the late 1940s, to perform spectrometric solar observations under dry and weakly polluted high-mountain conditions. Several solar atlases of photometric quality, extending altogether from the near-ultra-violet to the middle-infrared, were produced between 1956 and 1994, first with grating spectrometers then with Fourier transform instruments. During the early 1970s, scientific concerns emerged about atmospheric composition changes likely to set in as a consequence of the growing usage of nitrogen-containing agricultural fertilisers and the industrial production of chlorine-bearing compounds such as the chlorofluorocarbons and hydro-chlorofluorocarbons. Resulting releases to the atmosphere with ensuing photolysis in the stratosphere and catalytic depletion of the protective ozone layer prompted a worldwide consortium of chemical manufacturing companies to solicit the Liege group to help in clarifying these concerns by undertaking specific observations with its existing Jungfraujoch instrumentation. The following pages evoke the main steps that led from quasi full sun-oriented studies to priority investigations of the Earth's atmosphere, in support of both the Montreal and the Kyoto Protocols.

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See detailObservations of long-lived anthropogenic halocarbons at the high-Alpine site of Jungfraujoch (Switzerland) for assessment of trends and European sources
Reimann, Stefan; Vollmer, M. K.; Folini, Doris; Steinbacher, Martin; Hill, M.; Buchmann, Brigitte; Zander, Rodolphe; Mahieu, Emmanuel

in Science of the Total Environment (2008), 391

Anthropogenic halocarbons, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), bromocarbons (halons) and long-lived chlorinated solvents have been measured continuously at the high-Alpine site of Jungfraujoch (Switzerland) since January 2000. Chloro- and bromo-containing halocarbons are responsible for the stratospheric ozone depletion and will be globally banned from usage within the next years. With the exception of the stable CFC-12 (CF2Cl2), all major CFCs and chlorinated solvents show a negative trend in recent years in their background concentrations at Jungfraujoch. HCFCs, as their first-generation substitute, are still increasing with a few percent per year. However, the frequency and the strength of HCFCs pollution events, which are caused by regional European emissions, are already declining. This can be seen as a sign of the impending ban of these gases within the next years in Europe. On the other hand, HFCs as the second-generation substitutes, are increasing with relative rates of at least 10% per year (e.g. almost 5 ppt per year for HFC-134a). An allocation of European sources was attempted by combining measured concentrations with trajectories of air masses reaching the Jungfraujoch during pollution events. Potential source regions could be detected in Italy, France, Spain and Germany.

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See detailEvaluation of tropospheric and stratospheric ozone trends over Western Europe from ground-based FTIR network observations.
Vigouroux, C.; De Mazière, M.; Demoulin, Philippe; Servais, Christian; Hase, F.; Blumenstock, T.; Kramer, I.; Schneider, M.; Mellqvist, J.; Strandberg, A.; Velazco, V.; Notholt, J.; Sussmann, R.; Stremme, W.; Rockmann, A.; Gardiner, T.; Coleman, M.; Woods, P.

in Atmospheric Chemistry and Physics (2008), 362(8), 6865-6886

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See detailSpectroscopic detection of COClF in the tropical and mid-latitude lower stratosphere
Rinsland, Curtis P.; Nassar, Ray; Boone, Christopher D.; Bernath, Peter; Chiou, Linda; Weisenstein, Debra K.; Mahieu, Emmanuel; Zander, Rodolphe

in Journal of Quantitative Spectroscopy and Radiative Transfer (2007), 105(3), 467-475

We report retrievals of COClF (carbonyl chlorofluoride) based on atmospheric chemistry experiment (ACE) solar occultation spectra recorded at tropical and mid-latitudes during 2004-2005. The COClF molecule is a temporary reservoir of both chlorine and fluorine and has not been measured previously by remote sensing. A maximum COClF mixing ratio of 99.7 +/- 48.0 pptv (10(-12) per unit volume, 1 sigma) is measured at 28 km for tropical and subtropical occultations (latitudes below 20 degrees in both hemispheres) with lower mixing ratios at both higher and lower altitudes. Northern hemisphere mid-latitude mixing ratios (30-50 degrees N) resulted in an average profile with a peak mixing ratio of 51.7 +/- 132.1 pptv, 1 sigma, at 27 km, also decreasing above and below that altitude. We compare the measured average profiles with the one reported set of in situ lower stratospheric mid-latitude measurements from 1986 and 1987, a previous two-dimensional (2-D) model calculation for 1987 and 1993, and a 2-D-model prediction for 2004. The measured average tropical profile is in close agreement with the model prediction; the northern mid-latitude profile is also consistent, although the peak in the measured profile occurs at a higher altitude (2.5-4.5 km offset) than in the model prediction. Seasonal average 2-D-model predictions of the COClF stratospheric distribution for 2004 are also reported. (c) 2006 Elsevier Ltd. All rights reserved.

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See detailLong-term trends of tropospheric carbon monoxide and hydrogen cyanide from analysis of high resolution infrared solar spectra
Rinsland, Curtis P.; Goldman, Aaron; Hannigan, James W.; Wood, Stephen W.; Chiou, Linda S.; Mahieu, Emmanuel

in Journal of Quantitative Spectroscopy and Radiative Transfer (2007), 104(1), 40-51

Long-term trend and seasonal variation of the mean free tropospheric volume mixing ratios of carbon monoxide (CO) and hydrogen cyanide (HCN) have been derived from analysis of a time series of solar absorption spectra recorded from the US National Solar Observatory on Kitt Peak (31.9 degrees N, 111.6 degrees W, 2.09 km altitude) spanning almost three decades. The results of a fit to the CO 258 daily averages from May 1977 to April 2005 as a function of time with a model that assumes a sinusoidal seasonal cycle and a linear long-term trend with time yield a mean volume mixing ratio of 102 +/- 3) parts per billion (10(-9) per unit volume) below 10km altitude, I sigma. The CO measurements show a seasonal cycle with a maximum in March and a minimum in September with an amplitude of (22.3 +/- 1.5)% relative to the mean. The best-fit corresponds to a long-term CO trend of (0.15 +/- 0.14)% yr(-1), 1 sigma, relative to the mean. To quantify the possible impact of periods of intense fires, the CO measurements have been compared with the measurements of HCN, a well-documented emission product of biomass burning with a lifetime of similar to 5 months. The best fit to the full HCN time series of 208 daily averages from May 1978 to April 2005 results in a mean volume mixing ratio of (0.219 +/- 0.007) ppbv below 10 km altitude with a similar seasonal cycle, though with a lower relative amplitude than for CO. Although same-day enhancements up to a factor of 1.87 for HCN and 1.24 for CO were measured relative to values predicted by a fit to the time series that accounts for the seasonal cycles and trends of both molecules, excluding time periods of elevated fire emissions has no significant impact on the best-fit long-term free tropospheric CO and HCN trends. Our result of no long-term CO trend since the late 1970s suggests that the global average long-term decline reported from 1990 through 1995 measurements has not continued in the free troposphere. Similarly, a fit to the full time series of 208 HCN free tropospheric daily averages with the same model yields an average 2.09-10km mixing ratio of 0.219ppbv and a long-term trend of (-0.12 +/- 0.14) % yr(-1), 1 sigma, relative to the mean since 1978, also indicating no significant long-term trend above the lower mid-latitude continental US Kitt Peak station. The results for both molecules suggest the site was not significantly impacted by summer boreal fires during the time span of the measurements that in some years cause widespread pollution above northern higher latitude sites. (c) 2006 Elsevier Ltd. All rights reserved.

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See detailComparisons between ground-based FTIR and MIPAS N2O and HNO3 profiles before and after assimilation in BASCOE
Vigouroux, Corinne; De Mazière, Martine; Errera, Quentin; Chabrillat, Simon; Mahieu, Emmanuel; Duchatelet, Pierre; Wood, Stephen; Smale, Dan; Mikuteit, Sabine; Blumenstock, Thomas; Hase, Frank; Jones, Nicholas

in Atmospheric Chemistry and Physics (2007), 7

Within the framework of the Network for Detection of Atmospheric Composition Change (NDACC), regular ground-based Fourier transform infrared ( FTIR) measurements of many species are performed at several locations. Inversion schemes provide vertical profile information and characterization of the retrieved products which are therefore relevant for contributing to the validation of MIPAS profiles in the stratosphere and upper troposphere. We have focused on the species HNO3 and N2O at 5 NDACC-sites distributed in both hemispheres, i.e., Jungfraujoch (46.5 degrees N) and Kiruna (68 degrees N) for the northern hemisphere, and Wollongong (34 degrees S), Lauder (45 degrees S) and Arrival Heights (78 degrees S) for the southern hemisphere. These ground-based data have been compared with MIPAS offline profiles (v4.61) for the year 2003, collocated within 1000 km around the stations, in the lower to middle stratosphere. To get around the spatial collocation problem, comparisons have also been made between the same ground-based FTIR data and the corresponding profiles resulting from the stratospheric 4D-VAR data assimilation system BASCOE constrained by MIPAS data. This paper discusses the results of the comparisons and the usefullness of using BASCOE profiles as proxies for MIPAS data. It shows good agreement between MIPAS and FTIR N2O partial columns: the biases are below 5% for all the stations and the standard deviations are below 7% for the three mid-latitude stations, and below 10% for the high latitude ones. The comparisons with BASCOE partial columns give standard deviations below 4% for the mid-latitude stations to less than 8% for the high latitude ones. After making some corrections to take into account the known bias due to the use of different spectroscopic parameters, the comparisons of HNO3 partial columns show biases below 3% and standard deviations below 15% for all the stations except Arrival Heights ( bias of 5%, standard deviation of 21%). The results for this species, which has a larger spatial variability, highlight the necessity of defining appropriate collocation criteria and of accounting for the spread of the observed air-masses. BASCOE appears to have more deficiencies in producing proxies of MIPAS HNO3 profiles compared to N2O, but the obtained standard deviation of less than 10% between BASCOE and FTIR is reasonable. Similar results on profiles comparisons are also shown in the paper, in addition to partial column ones.

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See detailValidation of MIPAS ClONO2 measurements
Hopfner, Michael; von Clarmann, Thomas; Fischer, H.; Funke, B.; Glatthor, N.; Grabowski, Udo; Kellmann, S.; Kiefer, M.; Linden, A.; Milz, M.; Steck, T.; Stiller, G. P.; Bernath, Peter; Blom, C. E.; Blumenstock, Thomas; Boone, Christopher D.; Chance, Kelly; Coffey, M. T.; Friedl-Vallon, F.; Griffith, David; Hannigan, James W.; Hase, Frank; Jones, Nicholas; Jucks, Ken W.; Keim, C.; Kleinert, A.; Kouker, W.; Liu, G. Y.; Mahieu, Emmanuel; Mellqvist, Johan; Mikuteit, Sabine; Notholt, Justus; Oelhaf, H.; Piesch, C.; Reddmann, T.; Ruhnke, Roland; Schneider, Matthias; Strandberg, Anders; Toon, Geoffrey; Walker, Kaley A.; Warneke, Thorsten; Wetzel, G.; Wood, Stephen; Zander, Rodolphe

in Atmospheric Chemistry and Physics (2007), 7

Altitude profiles of ClONO2 retrieved with the IMK (Institut fur Meteorologie und Klimaforschung) science-oriented data processor from MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric Sounding on Envisat) mid-infrared limb emission measurements between July 2002 and March 2004 have been validated by comparison with balloon-borne (Mark IV, FIRS2, MIPAS-B), airborne (MIPAS-STR), ground-based (Spitsbergen, Thule, Kiruna, Harestua, Jungfraujoch, Izana, Wollongong, Lauder), and spaceborne (ACE-FTS) observations. With few exceptions we found very good agreement between these instruments and MIPAS with no evidence for any bias in most cases and altitude regions. For balloon-borne measurements typical absolute mean differences are below 0.05 ppbv over the whole altitude range from 10 to 39 km. In case of ACE-FTS observations mean differences are below 0.03 ppbv for observations below 26 km. Above this altitude the comparison with ACE-FTS is affected by the photochemically induced diurnal variation of ClONO2. Correction for this by use of a chemical transport model led to an overcompensation of the photochemical effect by up to 0.1 ppbv at altitudes of 30-35 km in case of MIPAS-ACE-FTS comparisons while for the balloon-borne observations no such inconsistency has been detected. The comparison of MIPAS derived total column amounts with ground-based observations revealed no significant bias in the MIPAS data. Mean differences between MIPAS and FTIR column abundances are 0.11 +/- 0.12 x 10(14) cm(-2) (1.0 +/- 1.1%) and -0.09 +/- 0.19 x 10(14) cm(-2) (-0.8 +/- 1.7%), depending on the coincidence criterion applied. chi(2) tests have been performed to assess the combined precision estimates of MIPAS and the related instruments. When no exact coincidences were available as in case of MIPAS-FTIR or MIPAS-ACE-FTS comparisons it has been necessary to take into consideration a coincidence error term to account for chi(2) deviations. From the resulting chi(2) profiles there is no evidence for a systematic over/underestimation of the MIPAS random error analysis.

See detailCommentary: Observational Aspects Related to the Chemical Evolution of our Atmosphere
Zander, Rodolphe

in Advances in Chemical Physics (2007)

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See detailValidation of MIPAS HNO3 operational data
Wang, D. Y.; Hopfner, Michael; Blom, C. E.; Ward, W. E.; Fischer, H.; Blumenstock, Thomas; Hase, Frank; Keim, C.; Liu, G. Y.; Mikuteit, Sabine; Oelhaf, H.; Wetzel, G.; Cortesi, U.; Mencaraglia, F.; Bianchini, G.; Redaelli, G.; Pirre, M.; Catoire, Valéry; Huret, Nathalie; Vigouroux, Corinne; De Mazière, Martine; Mahieu, Emmanuel; Demoulin, Philippe; Wood, Stephen; Smale, Dan; Jones, Nicholas; Nakajima, H.; Sugita, T.; Urban, J.; Murtagh, Donal; Boone, Christopher D.; Bernath, Peter; Walker, Kaley A.; Kuttippurath, Jayan; Kleinbohl, A.; Toon, Geoffrey C.; Piccolo, C.

in Atmospheric Chemistry and Physics (2007), 7(18), 4905-4934

Nitric acid (HNO3) is one of the key products that are operationally retrieved by the European Space Agency (ESA) from the emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. The product version 4.61/4.62 for the observation period between July 2002 and March 2004 is validated by comparisons with a number of independent observations from ground-based stations, aircraft/balloon campaigns, and satellites. Individual HNO3 profiles of the ESA MIPAS level-2 product show good agreement with those of MIPAS-B and MIPAS-STR (the balloon and aircraft version of MIPAS, respectively), and the balloon-borne infrared spectrometers MkIV and SPIRALE, mostly matching the reference data within the combined instrument error bars. In most cases differences between the correlative measurement pairs are less than 1 ppbv (5-10%) throughout the entire altitude range up to about 38 km (similar to 6 hPa), and below 0.5 ppbv (15-20% or more) above 30 km (similar to 17 hPa). However, differences up to 4 ppbv compared to MkIV have been found at high latitudes in December 2002 in the presence of polar stratospheric clouds. The degree of consistency is further largely affected by the temporal and spatial coincidence, and differences of 2 ppbv may be observed between 22 and 26 km (similar to 50 and 30 hPa) at high latitudes near the vortex boundary, due to large horizontal inhomogeneity of HNO3. Similar features are also observed in the mean differences of the MIPAS ESA HNO3 VMRs with respect to the ground-based FTIR measurements at five stations, aircraft-based SAFIRE-A and ASUR, and the balloon campaign IBEX. The mean relative differences between the MIPAS and FTIR HNO3 partial columns are within +/- 2%, comparable to the MIPAS systematic error of similar to 2%. For the vertical profiles, the biases between the MIPAS and FTIR data are generally below 10% in the altitudes of 10 to 30 km. The MIPAS and SAFIRE HNO3 data generally match within their total error bars for the mid and high latitude flights, despite the larger atmospheric inhomogeneities that characterize the measurement scenario at higher latitudes. The MIPAS and ASUR comparison reveals generally good agreements better than 10-13% at 20-34 km. The MIPAS and IBEX measurements agree reasonably well (mean relative differences within +/- 15%) between 17 and 32 km. Statistical comparisons of the MIPAS profiles correlated with those of Odin/SMR, ILAS-II, and ACE-FTS generally show good consistency. The mean differences averaged over individual latitude bands or all bands are within the combined instrument errors, and generally within 1, 0.5, and 0.3 ppbv between 10 and 40 km (similar to 260 and 4.5 hPa) for Odin/SMR, ILAS-II, and ACE-FTS, respectively. The standard deviations of the differences are between 1 to 2 ppbv. The standard deviations for the satellite comparisons and for almost all other comparisons are generally larger than the estimated measurement uncertainty. This is associated with the temporal and spatial coincidence error and the horizontal smoothing error which are not taken into account in our error budget. Both errors become large when the spatial variability of the target molecule is high.

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See detailOn the line parameters for the X 1sigma+g (1–0) infrared quadrupolar transitions of 14N2
Goldman, Aaron; Tipping, R.H.; Ma, Q.; Boone, C.D.; Bernath, P.F.; Demoulin, Philippe; Hase, Frank; Schneider, Matthias; Hannigan, J.W.; Coffey, M.T.; Rinsland, C.P.

in Journal of Quantitative Spectroscopy and Radiative Transfer (2007), 103

Re-examination of the 14N2 X 1sigma+g (1–0) line parameters in the HITRAN database showed that the vibration–rotation interaction effect on the line intensities has been neglected, and that the halfwidths are not compatible with experimental and theoretical studies. New line parameters have been generated, which improve the consistency and accuracy in individual N2 line retrievals from atmospheric spectra. Unresolved line shape issues require further studies.

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See detailGeophysical validation of MIPAS-ENVISAT operational ozone data
Cortesi, U.; Lambert, J. C.; De Clercq, C.; Bianchini, G.; Blumenstock, T.; Bracher, A.; Castelli, E.; Catoire, V.; Chance, K. V.; De Maziere, M.; Demoulin, Philippe; Godin-Beekmann, S.; Jones, N.; Jucks, K.; Keim, C.; Kerzenmacher, T.; Kuellmann, H.; Kuttippurath, J.; Iarlori, M.; Liu, G. Y.; Liu, Y.; McDermid, I. S.; Meijer, Y. J.; Mencaraglia, F.; Mikuteit, S.; Oelhaf, H.; Piccolo, C.; Pirre, M.; Raspollini, P.; Ravegnani, F.; Reburn, W. J.; Redaelli, G.; Remedios, J. J.; Sembhi, H.; Smale, D.; Steck, T.; Taddei, A.; Varotsos, C.; Vigouroux, C.; Waterfall, A.; Wetzel, G.; Wood, S.

in Atmospheric Chemistry and Physics (2007), 7(18), 4807-4867

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on-board the European ENVIronmental SATellite (ENVISAT) launched on 1 March 2002, is a middle infrared Fourier Transform spectrometer measuring the atmospheric emission spectrum in limb sounding geometry. The instrument is capable to retrieve the vertical distribution of temperature and trace gases, aiming at the study of climate and atmospheric chemistry and dynamics, and at applications to data assimilation and weather forecasting. MIPAS operated in its standard observation mode for approximately two years, from July 2002 to March 2004, with scans performed at nominal spectral resolution of 0.025 cm(-1) and covering the altitude range from the mesosphere to the upper troposphere with relatively high vertical resolution (about 3 km in the stratosphere). Only reduced spectral resolution measurements have been performed subsequently. MIPAS data were re-processed by ESA using updated versions of the Instrument Processing Facility (IPF v4.61 and v4.62) and provided a complete set of level-2 operational products (geo-located vertical profiles of temperature and volume mixing ratio of H2O, O-3, HNO3, CH4, N2O and NO2) with quasi continuous and global coverage in the period of MIPAS full spectral resolution mission. In this paper, we report a detailed description of the validation of MIPAS-ENVISAT operational ozone data, that was based on the comparison between MIPAS v4.61 (and, to a lesser extent, v4.62) O-3 VMR profiles and a comprehensive set of correlative data, including observations from ozone sondes, ground-based lidar, FTIR and microwave radiometers, remote-sensing and in situ instruments on-board stratospheric aircraft and balloons, concurrent satellite sensors and ozone fields assimilated by the European Center for Medium-range Weather Forecasting. A coordinated effort was carried out, using common criteria for the selection of individual validation data sets, and similar methods for the comparisons. This enabled merging the individual results from a variety of independent reference measurements of proven quality (i.e. well characterized error budget) into an overall evaluation of MIPAS O-3 data quality, having both statistical strength and the widest spatial and temporal coverage. Collocated measurements from ozone sondes and ground-based lidar and microwave radiometers of the Network for the Detection Atmospheric Composition Change (NDACC) were selected to carry out comparisons with time series of MIPAS O-3 partial columns and to identify groups of stations and time periods with a uniform pattern of ozone differences, that were subsequently used for a vertically resolved statistical analysis. The results of the comparison are classified according to synoptic and regional systems and to altitude intervals, showing a generally good agreement within the comparison error bars in the upper and middle stratosphere. Significant differences emerge in the lower stratosphere and are only partly explained by the larger contributions of horizontal and vertical smoothing differences and of collocation errors to the total uncertainty. Further results obtained from a purely statistical analysis of the same data set from NDACC ground-based lidar stations, as well as from additional ozone soundings at middle latitudes and from NDACC ground-based FTIR measurements, confirm the validity of MIPAS O-3 profiles down to the lower stratosphere, with evidence of larger discrepancies at the lowest altitudes. The validation against O-3 VMR profiles using collocated observations performed by other satellite sensors (SAGE II, POAM III, ODIN-SMR, ACE-FTS, HALOE, GOME) and ECMWF assimilated ozone fields leads to consistent results, that are to a great extent compatible with those obtained from the comparison with ground-based measurements. Excellent agreement in the full vertical range of the comparison is shown with respect to collocated ozone data from stratospheric aircraft and balloon instruments, that was mostly obtained in very good spatial and temporal coincidence with MIPAS scans. This might suggest that the larger differences observed in the upper troposphere and lowermost stratosphere with respect to collocated ground-based and satellite O-3 data are only partly due to a degradation of MIPAS data quality. They should be rather largely ascribed to the natural variability of these altitude regions and to other components of the comparison errors. By combining the results of this large number of validation data sets we derived a general assessment of MIPAS v4.61 and v4.62 ozone data quality. A clear indication of the validity of MIPAS O-3 vertical profiles is obtained for most of the stratosphere, where the mean relative difference with the individual correlative data sets is always lower than +/- 10%. Furthermore, these differences always fall within the combined systematic error (from 1 hPa to 50 hPa) and the standard deviation is fully consistent with the random error of the comparison (from 1 hPa to similar to 30-40 hPa). A degradation in the quality of the agreement is generally observed in the lower stratosphere and upper troposphere, with biases up to 25% at 100 hPa and standard deviation of the global mean differences up to three times larger than the combined random error in the range 50-100 hPa. The larger differences observed at the bottom end of MIPAS retrieved profiles can be associated, as already noticed, to the effects of stronger atmospheric gradients in the UTLS that are perceived differently by the various measurement techniques. However, further components that may degrade the results of the comparison at lower altitudes can be identified as potentially including cloud contamination, which is likely not to have been fully filtered using the current settings of the MIPAS cloud detection algorithm, and in the linear approximation of the forward model that was used for the a priori estimate of systematic error components. The latter, when affecting systematic contributions with a random variability over the spatial and temporal scales of global averages, might result in an underestimation of the random error of the comparison and add up to other error sources, such as the possible underestimates of the p and T error propagation based on the assumption of a 1 K and 2% uncertainties, respectively, on MIPAS temperature and pressure retrievals. At pressure lower than 1 hPa, only a small fraction of the selected validation data set provides correlative ozone data of adequate quality and it is difficult to derive quantitative conclusions about the performance of MIPAS O-3 retrieval for the topmost layers.

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See detailFirst space-based observations of formic acid (HCOOH): Atmospheric Chemistry Experiment austral spring 2004 and 2005 Southern Hemisphere tropical-mid-latitude upper tropospheric measurements
Rinsland, Curtis P.; Boone, Christopher D.; Bernath, Peter F.; Mahieu, Emmanuel; Zander, Rodolphe; Dufour, Gaëlle; Clerbaux, Catherine; Turquety, Solène; Chiou, Linda; McConnell, John C.; Neary, Lori; Kaminski, Jacek W.

in Geophysical Research Letters (2006), 33(23),

The first space-based measurements of upper tropospheric ( 110 - 300 hPa) formic acid (HCOOH) are reported from 0.02 cm(-1) resolution Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer solar occultation measurements at 16 degrees S - 43 degrees S latitude during late September to early October in 2004 and 2005. A maximum upper tropospheric HCOOH mixing ratio of 3.13 +/- 0.02 ppbv ( 1 ppbv = 10(-9) per unit volume), 1 sigma, at 10.5 km altitude was measured during 2004 at 29.97 degrees S latitude and a lower maximum HCOOH mixing ratio of 2.03 +/- 0.28 ppbv, at 9.5 km altitude was measured during 2005. Fire counts, back trajectories, and correlations of HCOOH mixing ratios with ACE simultaneous measurements of other fire products confirm the elevated HCOOH mixing ratios originated primarily from tropical fire emissions. A HCOOH emission factor relative to CO of 1.99 +/- 1.34 g kg(-1) during 2004 in upper tropospheric plumes is inferred from a comparison with lower mixing ratios measured during the same time period assuming HITRAN 2004 spectroscopic parameters.

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See detailAn empirical line-by-line model for the infrared solar transmittance spectrum from 700 to 5000 cm(-1)
Hase, F.; Demoulin, Philippe; Sauval, A. J.; Toon, G. C.; Bernath, P. F.; Goldman, A.; Hannigan, J. W.; Rinsland, C. P.

in Journal of Quantitative Spectroscopy and Radiative Transfer (2006), 102(3), 450-463

An empirical line-by-line model for the infrared solar transmittance spectrum is presented. The model can be incorporated into radiative transfer codes to allow fast calculation of all relevant emission and absorption features in the solar spectrum in the mid-infrared region from 700 to 5000 cm(-1). The transmittance is modelled as a function of the diameter of the field-of-view centered on the solar disk: the line broadening due to solar rotation as well as center-to-limb variations in strength and width are taken into account for stronger lines. Applications of the model presented here are in the fields of terrestrial remote sensing in the mid-infrared spectral region when the sun is used as radiation source or scattered solar radiation contributes to the measured signal and in the fields of atmospheric radiative transfer algorithms which compute the propagation of infrared solar radiation in the terrestrial atmosphere. (c) 2006 Elsevier Ltd. All rights reserved.

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See detailA global inventory of stratospheric chlorine in 2004
Nassar, Ray; Bernath, Peter; Boone, Christopher D.; Clerbaux, Catherine; Coheur, Pierre-François; Dufour, Gaëlle; Froidevaux, Lucien; Mahieu, Emmanuel; McConnell, John C.; McLeod, Sean D.; Murtagh, Donal; Rinsland, Curtis P.; Semeniuk, K.; Skelton, R.; Walker, Kaley A.; Zander, Rodolphe

in Journal of Geophysical Research. Atmospheres (2006), 111(D22), 22312

[1] Total chlorine (Cl-TOT) in the stratosphere has been determined using the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) measurements of HCl, ClONO2, CH3Cl, CCl4, CCl3F (CFC-11), CCl2F2 (CFC-12), CHClF2 (HCFC-22), CCl2FCClF2 (CFC-113), CH3CClF2 (HCFC-142b), COClF, and ClO supplemented by data from several other sources, including both measurements and models. Separate chlorine inventories were carried out in five latitude zones (60 degrees - 82 degrees N, 30 degrees - 60 degrees N, 30 degrees S - 30 degrees N, 30 degrees - 60 degrees S, and 60 degrees - 82 degrees S), averaging the period of February 2004 to January 2005 inclusive, when possible, to deal with seasonal variations. The effect of diurnal variation was avoided by only using measurements taken at local sunset. Mean stratospheric Cl-TOT values of 3.65 ppbv were determined for both the northern and southern midlatitudes (with an estimated 1 sigma accuracy of +/- 0.13 ppbv and a precision of +/- 0.09 ppbv), accompanied by a slightly lower value in the tropics and slightly higher values at high latitudes. Stratospheric Cl-TOT profiles in all five latitude zones are nearly linear with a slight positive slope in ppbv/km. Both the observed slopes and pattern of latitudinal variation can be interpreted as evidence of the beginning of a decline in global stratospheric chlorine, which is qualitatively consistent with the mean stratospheric circulation pattern and time lag necessary for transport.

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See detailA global inventory of stratospheric fluorine in 2004 based on Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) measurements
Nassar, Ray; Bernath, Peter F.; Boone, Christopher D.; Mc Leod, Sean; Skelton, Randall; Walker, Kaley; Rinsland, Curtis P.; Duchatelet, Pierre

in Journal of Geophysical Research (2006), 111

Total fluorine (FTOT) in the stratosphere has been determined using Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) measurements of HF, COF2, COClF, CF4, CCl3F (CFC-11), CCl2F2 (CFC-12), CHClF2 (HCFC-22), CCl2FCClF2 (CFC-113), CH3CClF2 (HCFC-142b), CH2FCF3 (HFC-134a), and SF6. The retrieval of HFC-134a (CH2FCF3) from spaceborne measurements had not been carried out prior to this work. Measurements of these species have been supplemented by data from models to extend the altitude range of the profiles and have also been complemented by estimates of 15 minor fluorine species. Using these data, separate fluorine budgets were determined in five latitude zones (60°–82°N, 30°–60°N, 30°S–30°N, 30°–60°S, and 60°–82°S) by averaging over the period of February 2004 to January 2005 inclusive, when possible. Stratospheric FTOT profiles in each latitude zone are nearly linear, with mean stratospheric FTOT values ranging from 2.50 to 2.59 ppbv (with a 1sig precision of 0.04–0.07 ppbv and an estimated accuracy of 0.15 ppbv) for each zone. The highest mean FTOT value occurred in the tropics, which is qualitatively consistent with increasing levels of stratospheric fluorine and the mean stratospheric circulation pattern.

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See detailComparisons between SCIAMACHY and ground-based FTIR data for total columns of CO, CH4, CO2 and N2O
Dils, Bart; De Mazière, Martine; Muller, Jean-François; Blumenstock, Thomas; Buchwitz, M.; de Beek, R.; Demoulin, Philippe; Duchatelet, Pierre; Fast, Hans; Frankenberg, Christian; Gloudemans, A.; Griffith, David; Jones, Nicholas; Kerzenmacher, Tobias; Kramer, Isabell; Mahieu, Emmanuel; Mellqvist, Johan; Mittermeier, Richard L.; Notholt, Justus; Rinsland, Curtis P.; Schrijver, H.; Smale, Dan; Strandberg, Anders; Straume, A. G.; Stremme, Wolfgang; Strong, Kimberley; Sussmann, Ralf; Taylor, Jeffrey; van den Broek, M.; Velazco, Voltaire; Wagner, T.; Warneke, Thorsten; Wiacek, A.; Wood, Stephen

in Atmospheric Chemistry and Physics (2006), 6

Total column amounts of CO, CH4, CO2 and N2O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based quasi-global network of Fourier-transform infrared ( FTIR) spectrometers. The SCIAMACHY data considered here have been produced by three different retrieval algorithms, WFM-DOAS (version 0.5 for CO and CH4 and version 0.4 for CO2 and N2O), IMAP- DOAS ( version 1.1 and 0.9 (for CO)) and IMLM (version 6.3) and cover the January to December 2003 time period. Comparisons have been made for individual data, as well as for monthly averages. To maximize the number of reliable coincidences that satisfy the temporal and spatial collocation criteria, the SCIAMACHY data have been compared with a temporal 3rd order polynomial interpolation of the ground-based data. Particular attention has been given to the question whether SCIAMACHY observes correctly the seasonal and latitudinal variability of the target species. The present results indicate that the individual SCIAMACHY data obtained with the actual versions of the algorithms have been significantly improved, but that the quality requirements, for estimating emissions on regional scales, are not yet met. Nevertheless, possible directions for further algorithm upgrades have been identified which should result in more reliable data products in a near future.

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See detailLong-term trend of CH4 at northern mid-latitudes: Comparison between ground-based infrared solar and surface sampling measurements
Rinsland, Curtis P.; Goldman, Aaron; Elkins, James W.; Chiou, Linda S.; Hannigan, James W.; Wood, Stephen W.; Mahieu, Emmanuel; Zander, Rodolphe

in Journal of Quantitative Spectroscopy and Radiative Transfer (2006), 97(3), 457-466

We report average tropospheric CH4 volume mixing ratios retrieved from a 27 year time series of high spectral resolution infrared solar absorption measurements recorded between May 1977 and July 2004 at the US National Solar Observatory station on Kitt Peak (31.9 degrees N, 111.6 degrees W, 2.09 km altitude) and their comparison with surface in situ sampling measurements recorded between 1983 and 2004 at the Climate Monitoring and Diagnostics Laboratory (CMDL) station at Niwot Ridge, Colorado (40.0 degrees N, 105.5 degrees W, 3013 m altitude). The two measurement sets therefore overlap for the 1983-2004 time period. An average tropospheric volume mixing ratios of 1814 +/- 48 ppbv (1 ppbv = 10(-9) per unit volume) has been derived from the solar absorption time series with a best-fit increase rate trend equal to 8.26 +/- 2.20 ppbv yr(-1) in 1983 decreasing to 1.94 +/- 3.69 ppbv yr(-1) in 2003. The CMDL measurements also show a continuous long-term CH4 volume mixing ratio rise, with subsequent slowing down. A mean ratio of the retrieved average tropospheric volume mixing ratio to the CMDL volume mixing ratio for the overlapping time period of 1.038 +/- 0.034 indicates agreement between both data sets within the quantified experimental errors. (C) 2005 Elsevier Ltd. All rights reserved.

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See detailLine-by-line calculations of thermal infrared radiation representative for global condition: CFC-12 as an example
Myhre, Gunnar; Stordal, Frode; Gausemel, Ingvil; Nielsen, Claus J.; Mahieu, Emmanuel

in Journal of Quantitative Spectroscopy and Radiative Transfer (2006), 97(3), 317-331

We estimate a current direct radiative forcing due to CFC-12 of 0.18 Wm(-2), which is likely to be the peak radiative forcing for CFC-12. Global measurements of CFC-12 show at present an almost negligible trend for CFC-12 and measurement in an industrialized region show evidence that the peak concentration is reached. It is expected that concentration of CFC-12 in industrialized regions begins to decline 1-3 years before the global concentration. Our radiative forcing calculations are based on a line-by-line model appropriate for simulation of global mean radiative forcing, including clouds and stratospheric temperature adjustment. The radiative forcing of 0.33 Wm(-2)/ppbv is close to earlier published results for this compound. New spectroscopic measurements for CFC-12 are performed and compared to previously published results. (C) 2005 Elsevier Ltd. All rights reserved.

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See detailLong-term stratospheric carbon tetrafluoride (CF4) increase inferred from 1985-2004 infrared space-based solar occultation measurements
Rinsland, Curtis P.; Mahieu, Emmanuel; Zander, Rodolphe; Nassar, Ray; Bernath, Peter; Boone, Christopher D.; Chiou, Linda S.

in Geophysical Research Letters (2006), 33(2),

The long-term stratospheric carbon tetrafluoride (CF4) increase has been determined from infrared high spectral resolution solar occultation Fourier transform spectrometer measurements between 3 and 50 hPa (similar to 20 to 40 km altitude) and latitudes from 50 degrees N to 50 degrees S during 1985, 1992, 1993, 1994, and 2004. The 1985 to 1994 measurements were recorded from the ATMOS ( Atmospheric Trace MOlecule Spectroscopy) instrument at 0.01 cm(-1) resolution and in 2004 by the Atmospheric Chemistry Experiment ( ACE) instrument at 0.02 cm(-1) resolution. Stratospheric volume mixing ratios, inferred from a polynomial fit to averages from the time periods considered here, increased from 49.37 +/- 2.60 pptv (10(-12) per unit volume) in 1985 to 58.38 +/- 4.14 pptv in 1992, 60.46 +/- 2.97 pptv in 1993, 60.11 +/- 3.60 pptv in 1994 and to 70.45 +/- 3.40 pptv in 2004. The stratospheric CF4 mixing ratio has continued to increase but at a slower rate than in previous years, for example, (1.14 +/- 0.68)% yr(-1) in 2004 as compared to (2.77 +/- 0.47)% yr(-1) in 1985, 1 sigma. Correlations of CF4 with N2O taking into account the increase of N2O with time also show the increase in the stratospheric CF4 burden over the two decade measurement time span. Our space-based measurements show that the slowdown in the rate of CF4 accumulation previously reported from surface measurements through 1997 has propagated to the stratosphere and is continuing. Citation: Rinsland, C. P., E. Mahieu, R. Zander, R. Nassar, P. Bernath, C. Boone, and L. S. Chiou (2006), Long-term stratospheric carbon tetrafluoride (CF4) increase inferred from 1985-2004 infrared space-based solar occultation measurements, Geophys. Res. Lett., 33, L02808, doi:10.1029/2005GL024709.

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See detailLine narrowing effect on the retrieval of HF and HCl vertical profiles from ground-based FTIR measurements
Barret, Brice; Hurtmans, Daniel; Carleer, Michel R.; De Mazière, Martine; Mahieu, Emmanuel; Coheur, Pierre-François

in Journal of Quantitative Spectroscopy and Radiative Transfer (2005), 95(4), 499-519

Collision-induced line narrowing, which has been discovered in the 1950s and investigated thoroughly in the laboratory since then, has yet never been taken into account in the spectroscopic remote sensing of the atmosphere. This work investigates the effect of collision-induced line narrowing onto the retrieval of HCl and HF vertical profiles from ground-based solar absorption FTIR measurements made at the NDSC station of the Jungfraujoch (46.5 degrees N, 8 degrees E and 3580 m above see level). The retrievals are performed with the Atmosphit software, recently developed at the Universite Libre de Bruxelles. It is presented in this paper for the first time and is validated against the widely used SFIT2 software. The impact of the line narrowing onto the retrieval of HCl and HF vertical profiles is examined relying on careful information content and error budget analyses. We report that the effect is relatively weak for HCl but significant for HF. Confirmation of the need to take the line narrowing into account for the retrieval of vertical profiles from ground-based FTIR spectra is given by comparison with data from the HALOE space borne instrument, rather insensitive to this spectroscopic effect. (c) 2005 Elsevier Ltd. All rights reserved.

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See detailTrends of HF, HCl, CCl2F2, CCl3F, CHClF2 (HCFC-22), and SF6 in the lower stratosphere from Atmospheric Chemistry Experiment (ACE) and Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements near 30 degrees N latitude
Rinsland, Curtis P.; Boone, Christopher D.; Nassar, Ray; Walker, Kaley A.; Bernath, Peter; Mahieu, Emmanuel; Zander, Rodolphe; McConnell, John C.; Chiou, Linda S.

in Geophysical Research Letters (2005), 32(16),

[ 1] Volume mixing ratios ( VMRs) of HF, HCl, CCl2F2, CHClF2 ( HCFC-22), and SF6 in the lower stratosphere have been derived from solar occultation measurements recorded with spaceborne high resolution Fourier transform spectrometers. Atmospheric Chemistry Experiment ( ACE) VMRs measured during 2004 have been compared with those obtained in 1985 and 1994 by the Atmospheric Trace MOlecule Spectroscopy ( ATMOS) instrument. Trends are estimated by referencing the measured VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled air masses. Pressure-gridded measurements covering 10-100 hPa ( similar to 16 to 30 km altitude) were used in the analysis that includes typically 25 degrees N-35 degrees N latitude. The VMR changes provide further evidence of the impact of the emission restrictions imposed by the Montreal Protocol and its strengthening amendments and adjustments and are consistent with model predictions and known sources and sinks of halocarbons. Decreases in the lower stratospheric mixing ratios of CCl3F and HCl are measured in 2004 with respect to 1994, providing important confirmation of recent ground-based solar absorption measurements of a decline in inorganic chlorine. Trends estimates are compared with other reported measurements and model predictions.

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See detailComparisons between ACE-FTS and ground-based measurements of stratospheric HCl and ClONO2 loadings at northern latitudes
Mahieu, Emmanuel; Zander, Rodolphe; Duchatelet, Pierre; Hannigan, Jim W.; Coffey, M. T.; Mikuteit, Sabine; Hase, Frank; Blumenstock, Thomas; Wiacek, Aldona; Strong, Kimberley; Taylor, Jeffrey R.; Mittermeier, Richard L.; Fast, Hans; Boone, Christopher D.; McLeod, Sean D.; Walker, Kaley A.; Bernath, Peter; Rinsland, Curtis P.

in Geophysical Research Letters (2005), 32(15),

We report first comparisons of stratospheric column abundances of hydrogen chloride (HCl) and chlorine nitrate (ClONO2) derived from infrared solar spectra recorded in 2004 at selected northern latitudes by the spaceborne Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) and by Fourier transform infrared (FTIR) instruments at the NDSC (Network for Detection of Stratospheric Change)-affiliated sites of Thule ( Greenland), Kiruna ( Sweden), Jungfraujoch ( Switzerland), and Egbert and Toronto ( Canada). Overall, and within the respective uncertainties of the independent measurement approaches, the comparisons show that the ACE-FTS measurements produce very good stratospheric volume mixing ratio profiles. Their internal precision allows to identify characteristic distribution features associated with latitudinal, dynamical, seasonal and chemical changes occurring in the atmosphere.

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See detailAtmospheric Chemistry Experiment (ACE): Mission overview
Bernath, Peter; McElroy, C. T.; Abrams, Mark; Boone, Christopher D.; Butler, Mike; Camy-Peyret, Claude; Carleer, Michel; Clerbaux, Catherine; Coheur, Pierre-François; Colin, Réginald; DeCola, P.; De Mazière, Martine; Drummond, J. R.; Dufour, Gaelle; Evans, W. F. J.; Fast, Hans; Fussen, Didier; Gilbert, Kathy; Jennings, D. E.; Llewellyn, E. J.; Lowe, R. P.; Mahieu, Emmanuel; McConnell, John C.; McHugh, M.; McLeod, Sean D.; Michaud, R.; Midwinter, C.; Nassar, Ray; Nichitiu, F.; Nowlan, C.; Rinsland, Curtis P.; Rochon, Y. J.; Rowlands, N.; Semeniuk, K.; Simon, Paul; Skelton, R.; Sloan, J. J.; Soucy, Marc-André; Strong, Kimberley; Tremblay, P.; Turnbull, D.; Walker, Kaley A.; Walkty, I.; Wardle, D. A.; Wehrle, V.; Zander, Rodolphe; Zou, J.

in Geophysical Research Letters (2005), 32(15),

SCISAT-1, also known as the Atmospheric Chemistry Experiment ( ACE), is a Canadian satellite mission for remote sensing of the Earth's atmosphere. It was launched into low Earth circular orbit ( altitude 650 km, inclination 74 degrees) on 12 Aug. 2003. The primary ACE instrument is a high spectral resolution (0.02 cm(-1)) Fourier Transform Spectrometer (FTS) operating from 2.2 to 13.3 mm ( 750 - 4400 cm(-1)). The satellite also features a dual spectrophotometer known as MAESTRO with wavelength coverage of 285 - 1030 nm and spectral resolution of 1 - 2 nm. A pair of filtered CMOS detector arrays records images of the Sun at 0.525 and 1.02 mu m. Working primarily in solar occultation, the satellite provides altitude profile information ( typically 10 - 100 km) for temperature, pressure, and the volume mixing ratios for several dozen molecules of atmospheric interest, as well as atmospheric extinction profiles over the latitudes 85 degrees N to 85 degrees S. This paper presents a mission overview and some of the first scientific results.

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See detailEvolution of a dozen non-CO2 greenhouse gases above central Europe since the mid-1980s
Zander, Rodolphe; Mahieu, Emmanuel; Demoulin, Philippe; Duchatelet, Pierre; Servais, Christian; Roland, Ginette; Delbouille, Luc; De Mazière, Martine; Rinsland, Curtis P.

in Environmental Sciences (2005), 2(2-3), 295-303

High-resolution infrared solar observations have been conducted consistently since the mid-1980s at the International Scientific Station of the Jungfraujoch, Switzerland, by the GIRPAS-ULg team (Groupe Infra-Rouge de Physique Atmosphrique et Solaire-University of Lige), and by colleagues from the Belgian Institute for Space Aeronomy and from the Royal Observatory of Belgium, Brussels. These observations were performed with state-of-the-art Fourier transform infrared (FTIR) spectrometers, revealing specific absorption features of over 20 atmospheric gases in the middle-infrared. Related spectrometric analyses have allowed the derivation of their burdens, seasonal and inter-annual variability, as well as their long-term evolution. In addition to updates of long-term changes for CCl2F2, CHClF2, CH4, N2O, SF6, CO, C2H6 and C2H2 already dealt with at previous Non-CO2 Greenhouse Gases (NCGG) symposia, this paper further reports temporal evolutions observed during the past two decades for a series of other source gases, namely OCS, HCN, CCl3F and CCl4, which also have direct or indirect effects on the radiation balance of the troposphere and on the stratospheric ozone layer.

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See detailSulphur hexafluoride (SF6): comparison of FTIR-measurements at three sites and determination of its trend in the northern hemisphere
Krieg, Juergen; Notholt, Justus; Mahieu, Emmanuel; Rinsland, Curtis P.; Zander, Rodolphe

in Journal of Quantitative Spectroscopy and Radiative Transfer (2005), 92(3), 383-392

Fourier transform infrared spectrometry has been used to retrieve the total column abundances of SF6 at three locations in the northern hemisphere, i.e., the Ny- Angstromlesund site in Spitsbergen/Norway at 79degreesN, the Jungfraujoch observatory in Switzerland at 47degreesN and the Kitt Peak observatory in Arizona, USA, at 32degreesN. The total column results have been converted to average tropospheric mixing ratios. The mean increases in these mixing ratios have been found to be, equal to 0.31 +/- 0.08 pptv yr(-1) at Ny Angstromlesund, 0.24 +/- 0.01 pptv yr(-1) at the Jungfraujoch and 0.28 +/- 0.09 pptv yr(-1) at Kitt Peak for the common period March 1993 to March 2002, in agreement with corresponding CMDL data (0.21 +/- 0.0002 pptv yr(-1)) at the surface. The limited accuracy of the Ny Angstromlesund and Kitt Peak data results from strong tropospheric water vapour interferences at these lower altitude sites. Observations at all three locations show that SF6 is Still accumulating in the atmosphere. Extrapolations of linear and second-order fits to the Jungfraujoch data predict tropospheric mixing ratios of SF6, respectively equal to 16.4 +/- 0.5 and. 14.7 +/- 0.6 in 2050, and 28.2 +/- 0.9 and 22.2 +/- 10.8 pptv in 2100, significantly, lower than those reported in the literature so far. (C) 2004 Elsevier Ltd. All, rights reserved.

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See detailLong-term evolution in the tropospheric concentration of chlorofluorocarbon 12 (CCl2F2) derived from high-spectral resolution infrared solar absorption spectra: retrieval and comparison with in situ surface measurements
Rinsland, Curtis P.; Goldman, Aaron; Mahieu, Emmanuel; Zander, Rodolphe; Chiou, Linda S.; Hannigan, James W.; Wood, Stephen W.; Elkins, James W.

in Journal of Quantitative Spectroscopy and Radiative Transfer (2005), 92(2), 201-209

The average tropospheric volume mixing ratios of chlorofluorocarbon 12 (CCl2F2) have been retrieved from high-spectral resolution ground-based infrared solar-absorption spectra recorded from March 1982 to October 2003 with the McMath Fourier transform spectrometer at the US National Solar Observatory facility on Kitt Peak in southern Arizona (31.9degreesN, 111.6degreesW, 2.09 km altitude). The retrievals are based on fits to the unresolved v(8) band Q-branches near 922 cm(-1) using the SFIT2 retrieval algorithm. The annual increase rate was equal to (16.88 +/- 1.37) parts per trillion (10(-12)) by volume at the beginning of the time series, March 1982, or (4.77 +/- 0.04)%, 1 sigma, declining progressively to (2.49 +/- 1.24) parts per trillion, by volume at the end, October 2003, or (0.46 +/- 0.24)%, 1 sigma. Average tropospheric mixing ratios from the solar spectra have been compared with average surface flask and in situ sampling measurements from the Climate Monitoring and Diagnostics Laboratory (CMDL) station at Niwot Ridge, CO, (USA) (40.0degreesN, 105.5degreesW, 3013 m altitude). The average ratio and standard deviation of the monthly means of the retrieved tropospheric mixing ratios relative to the CMDL surface mixing ratios is (1.01 +/- 0.03) for the overlapping time period. Both datasets demonstrate the progressive impact of the Montreal protocol and its strengthening amendments on the trend of CCl2F2, though a tropospheric decrease has yet to be observed. (C) 2004 Elsevier Ltd. All rights reserved.

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See detailIncreased Northern Hemispheric carbon monoxide burden in the troposphere in 2002 and 2003 detected from the ground and from space
Yurganov, Leonid N.; Duchatelet, Pierre; Dzhola, A. V.; Edwards, David P.; Hase, Frank; Kramer, Isabell; Mahieu, Emmanuel; Mellqvist, Johan; Notholt, Justus; Novelli, Paul C.; Rockmann, A.; Scheel, H. E.; Schneider, Matthias; Schulz, A.; Strandberg, Anders; Sussmann, Ralf; Tanimoto, H.; Velazco, Voltaire; Drummond, J. R.; Gille, J. C.

in Atmospheric Chemistry and Physics (2005), 5

Carbon monoxide total column amounts in the atmosphere have been measured in the High Northern Hemisphere (30degrees - 90degrees N, HNH) between January 2002 and December 2003 using infrared spectrometers of high and moderate resolution and the Sun as a light source. They were compared to ground-level CO mixing ratios and to total column amounts measured from space by the Terra/MOPITT instrument. All these data reveal increased CO abundances in 2002 - 2003 in comparison to the unperturbed 2000 - 2001 period. Maximum anomalies were observed in September 2002 and August 2003. Using a simple two-box model, the corresponding annual CO emission anomalies (referenced to 2000 - 2001 period) have been found equal to 95 Tg in 2002 and 130 Tg in 2003, thus close to those for 1996 and 1998. A good correlation with hot spots detected by a satellite radiometer allows one to assume strong boreal forest fires, occurred mainly in Russia, as a source of the increased CO burdens.

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See detailThe exploitation of ground-based Fourier transform infrared observations for the evaluation of tropospheric trends of greenhouse gases over Europe
De Mazière, Martine; Vigouroux, Corinne; Gardiner, Tom; Coleman, M.; Woods, Peter; Ellingsen, Kjerstin; Gauss, Michael; Isaksen, Ivar; Blumenstock, Thomas; Hase, Frank; Kramer, Isabell; Camy-Peyret, Claude; Chelin, Pascale; Mahieu, Emmanuel; Demoulin, Philippe; Duchatelet, Pierre; Mellqvist, Johan; Strandberg, Anders; Velazco, Voltaire; Notholt, Justus; Sussmann, Ralf; Stremme, Wolfgang; Rockmann, A.

in Environmental Sciences (2005), 2(2-3), 283-293

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including non-CO2 greenhouse gases. Such observations have regularly been made for many years as a contribution to the Network for the Detection of Stratospheric Change (NDSC). They are the only ground-based remote sensing observations available nowadays that carry information about a number of greenhouse gases in the free troposphere. This work focuses on the discussion of the information content of FTIR long-term monitoring data of some direct and indirect greenhouse gases (CH4, N2O, O3 and CO and C2H6, respectively), at six NDSC stations in Western Europe. This European FTIR network covers the polar to subtropical regions. At several stations of the network, the observations span more than a decade. Existing spectral time series have been reanalyzed according to a common optimized retrieval strategy, in order to derive distinct tropospheric and stratospheric abundances for the above-mentioned target gases. A bootstrap resampling method has been implemented to evaluate trends of the tropospheric burdens of the target gases, including their uncertainties. In parallel, simulations of the target time series are being made with the Oslo CTM2 model: comparisons between the model results and the observations provide valuable information to improve the model and, in particular, to optimize emission estimates that are used as inputs to the model simulations. The work is being performed within the EC project UFTIR. The paper focuses on N2O for which the first trend results have been obtained.

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See detailFree tropospheric measurements of formic acid (HCOOH) from infrared ground-based solar absorption spectra: Retrieval approach, evidence for a seasonal cycle, and comparison with model calculations
Rinsland, Curtis P.; Mahieu, Emmanuel; Zander, Rodolphe; Goldman, Aaron; Wood, Steven; Chiou, Linda

in Journal of Geophysical Research. Atmospheres (2004), 109(D18),

The seasonal variation of the free tropospheric volume mixing ratio of formic acid (HCOOH) has been derived from high-spectral-resolution solar absorption spectra recorded with the Fourier transform spectrometer in the U. S. National Solar Observatory facility on Kitt Peak (31.9degreesN, 111.6degreesE, 2.09 km altitude) at a typical spectral resolution of 0.005 cm(-1). The spectra have been analyzed with the SFIT2 algorithm, which is based on a semiempirical application of the optimal estimation method. Absorption by HCOOH is weak in these solar spectra, but successful retrievals have been obtained with a new procedure that fits the HCOOH nu(6) band Q branch at 1105 cm(-1) simultaneously with a window to account for a temperature-sensitive HDO line, which overlaps the HCOOH Q branch. After retaining only the best measurements from a database extending from June 1980 to October 2002 the retrievals show a seasonal variation, with a summer maximum and a winter minimum. Average 2.09-10 km volume mixing ratios binned in 3 month intervals range from a maximum of 792+/-323 parts per trillion by volume (pptv), or 10(-12), in July-September to a minimum of 313+/-175 pptv in October-December, with the uncertainties corresponding to statistical means from daily averages. The results are compared with previously reported measurements and model calculations.

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See detailA quantitative assessment of the 1998 carbon monoxide emission anomaly in the Northern Hemisphere based on total column and surface concentration measurements
Yurganov, Leonid N.; Blumenstock, Thomas; Grechko, E. I.; Hase, Frank; Hyer, E. J.; Kasischke, E. S.; Koike, M.; Kondo, Y.; Kramer, Isabell; Leung, F. Y.; Mahieu, Emmanuel; Mellqvist, Johan; Notholt, Justus; Novelli, Paul C.; Rinsland, Curtis P.; Scheel, H. E.; Schulz, A.; Strandberg, Anders; Sussmann, Ralf; Tanimoto, H.; Velazco, Voltaire; Zander, Rodolphe; Zhao, Y.

in Journal of Geophysical Research. Atmospheres (2004), 109(D15),

Carbon monoxide abundances in the atmosphere have been measured between January 1996 and December 2001 in the high Northern Hemisphere (HNH) (30degrees-90degreesN) using two different approaches: total column amounts of CO retrieved from infrared solar spectra and CO mixing ratios measured in situ at ground-based stations. The data were averaged, and anomalies of the CO HNH burden ( deviations of the total tropospheric mass between 30degreesN and 90degreesN from the mean seasonal profile, determined as the 5 year average) were analyzed. The anomalies obtained from in situ and total column data agree well and both show two maxima, by far the largest in October 1998 and a lower one in August 1996. A noticeable decrease of the positive 1998 summer anomaly with increasing height was found. A box model was applied, and anomalies in source rates were obtained under the assumption of insignificant interannual sink variations. In August 1998 the HNH emission anomaly was estimated to be 38 Tg month(-1). The annual 1998 emission positive anomaly was 96 Tg yr(-1). Nearly all excess CO may be attributed to the emissions from boreal forest fires. According to available inventories, biomass burning emits around 52 Tg yr(-1) during the "normal'' years; therefore total biomass emissions in 1998 were as large as 148 Tg yr(-1). In August 1998, CO contribution from the biomass burning was twice as large as that from fossil fuel combustion. The results were compared to available emission inventories.

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See detailGround-based FTIR measurements of CO from the Jungfraujoch: characterisation and comparison with in situ surface and MOPITT data
Barret, Brice; De Mazière, Martine; Mahieu, Emmanuel

in Atmospheric Chemistry and Physics (2003), 3

CO vertical profiles have been retrieved from solar absorption FTIR spectra recorded at the NDSC station of the Jungfraujoch ( 46.5 degreesN, 8degrees E and 3580 ma. s. l.) for the period from January 1997 to May 2001. The characterisation of these profiles has been established by an information content analysis and an estimation of the error budgets. A partial validation of the profiles has been performed through comparisons with correlative measurements. The average volume mixing ratios ( vmr) in the 3 km layer above the station have been compared with coincident surface measurements. The agreement between monthly means from both measurement techniques is very good, with a correlation coefficient of 0.87, and no significant bias observed. The FTIR total columns have also been compared to CO partial columns above 3580 ma. s. l. derived from the MOPITT ( Measurement Of Pollution In The Troposphere) instrument for the period March 2000 to May 2001. Relative to the FTIR columns, the MOPITT partial columns exhibit a positive bias of 8 +/- 8% for daytime and of 4 +/- 7% for nighttime measurements.

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See detailPost-Mount Pinatubo eruption ground-based infrared stratospheric column measurements of HNO3, NO, and NO2 and their comparison with model calculations
Rinsland, Curtis P.; Weisenstein, Debra K.; Ko, Malcolm K. W.; Scott, C. J.; Chiou, Linda S.; Mahieu, Emmanuel; Zander, Rodolphe; Demoulin, Philippe

in Journal of Geophysical Research. Atmospheres (2003), 108(D15),

[1] Infrared solar spectra recorded between July 1991 to March 1992 and November 2002 with the Fourier transform spectrometer on Kitt Peak (31.9 degrees N latitude, 111.6 degrees W longitude, 2.09 km altitude) have been analyzed to retrieve stratospheric columns of HNO3, NO, and NO2. The measurements cover a decade time span following the June 1991 Mount Pinatubo volcanic eruption and were recorded typically at 0.01 cm(-1) spectral resolution. The measured HNO3 stratospheric column shows a 20% decline from 9.16 x 10(15) molecules cm(-2) from the first observation in March 1992 to 7.40 x 10(15) molecules cm(-2) at the start of 1996 reaching a broad minimum of 6.95 x 10(15) molecules cm(-2) thereafter. Normalized daytime NO and NO2 stratospheric column trends for the full post-Pinatubo eruption time period equal (+ 1.56 +/- 0.45)% yr(-1), 1 sigma, and (+ 0.52 +/- 0.32)% yr(-1), 1 sigma, respectively. The long-term trends are superimposed on seasonal cycles with ~10% relative amplitudes with respect to mean values, winter maxima for HNO3 and summer maxima for NO and NO2. The measurements have been compared with two-dimensional model calculations utilizing version 6.1 Stratospheric Aerosol and Gas Experiment ( SAGE) II sulfate aerosol surface area density measurements through 1999 and extended to the end of the time series by repeating the 1999 values. The model-calculated HNO3, NO, and NO2 stratospheric column time series agree with the measurements to within ~8% after taking into account the vertical sensitivity of the ground-based measurements. The consistency between the measured and model-calculated stratospheric time series confirms the decreased impact on stratospheric reactive nitrogen chemistry of the key heterogeneous reaction that converts reactive nitrogen to its less active reservoir form as the lower-stratospheric aerosol surface area density declined by a factor of ~20 after the eruption maximum.

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See detailLong-term trends of inorganic chlorine from ground-based infrared solar spectra: Past increases and evidence for stabilization
Rinsland, Curtis P.; Mahieu, Emmanuel; Zander, Rodolphe; Jones, Nicholas B.; Chipperfield, Martyn P.; Goldman, Aaron; Anderson, John; Russell III, Jim M.; Demoulin, Philippe; Notholt, Justus; Toon, Geoffrey C.; Blavier, Jean-François; Sen, Bashwar; Sussmann, Ralf; Wood, Stephen W.; Meier, Arndt; Griffith, Dave W. T.; Chiou, Linda S.; Murcray, Frank J.; Stephen, T. M.; Hase, Frank; Mikuteit, Sabine; Shulz, Astrid; Blumenstock, Thomas

in Journal of Geophysical Research (2003), 108(D8), 4252

Long-term time series of hydrogen chloride (HCl) and chlorine nitrate (ClONO2) total column abundances has been retrieved from high spectral resolution ground-based solar absorption spectra recorded with infrared Fourier transform spectrometers at nine NDSC (Network for the Detection of Stratospheric Change) sites in both Northern and Southern Hemispheres. The data sets span up to 24 years and most extend until the end of 2001. The time series of Cly (defined here as the sum of the HCl and ClONO2 columns) from the three locations with the longest time-span records show rapid increases until the early 1990s superimposed on marked day-to-day, seasonal and inter-annual variability. Subsequently, the buildup in Cly slows and reaches a broad plateau after 1996, also characterized by variability. A similar time evolution is also found in the total chlorine concentration at 55 km altitude derived from Halogen Occultation Experiment (HALOE) global observations since 1991. The stabilization of inorganic chlorine observed in both the total columns and at 55 km altitude indicates that the near-global 1993 organic chlorine (CCly) peak at the Earth’s surface has now propagated over a broad altitude range in the upper atmosphere, though the time lag is difficult to quantify precisely from the current data sets, due to variability. We compare the three longest measured time series with two-dimensional model calculations extending from 1977 to 2010, based on a halocarbon scenario that assumes past measured trends and a realistic extrapolation into the future. The model predicts broad Cly maxima consistent with the long-term observations, followed by a slow Cly decline reaching 12–14% relative to the peak by 2010. The data reported here confirm the effectiveness of the Montreal Protocol and its Amendments and Adjustments in progressively phasing out the major man-related perturbations of the stratospheric ozone layer, in particular, the anthropogenic chlorine-bearing source gases.

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See detailSF6 ground-based infrared solar absorption measurements: long-term trend, pollution events, and a search for SF5CF3 absorption
Rinsland, Curtis P.; Goldman, Aaron; Stephen, T. M.; Chiou, Linda S.; Mahieu, Emmanuel; Zander, Rodolphe

in Journal of Quantitative Spectroscopy and Radiative Transfer (2003), 78(1), 41-53

Infrared solar spectra recorded with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak (31.9degreesN latitude, 111.6degreesW, 2.09 km altitude), southwest of Tucson, Arizona, have been analyzed to retrieve average SF6 tropospheric mixing ratios over a two-decade time span. The analysis is based primarily on spectral fits to absorption by the intense, unresolved nu(3) band Q branch at 947.9 cm(-1). A best fit to measurements recorded with SF6 near typical background concentrations yields a SF6 increase in the average tropospheric mixing ratio from 1.13 pptv (10(-12) per unit volume) in March 1982 to 3.77 pptv in March 2002. The long-term increase by a factor of 3.34 over the time span is consistent with the rapid growth of surface mixing ratios measured in situ at Northern Hemisphere remote stations, though the infrared measurements show a large scatter. Average tropospheric mixing ratio enhancements above background by 2-3 orders of magnitude have been identified in spectra recorded on 5 days between November 1988 and April 1997. These spectra were individually analyzed in an attempt to detect the strongest 8-12 mum band of SF5CF3, a molecule recently identified with an atmospheric growth that has closely paralleled the rise in SF6 during the past three decades. Absorption by the strongest SF5CF3 band was predicted to be above the noise level in the Kitt Peak spectrum with the highest average mean tropospheric SF6 mixing ratio, assuming the reported atmospheric SF5CF3/SF6 ratio and a room temperature absorption cross sections reported for the SF5CF3 903-cm(-1) band. An upper limit of 8 x 10(15) molecules cm(-2) for the SF5CF3 total column was estimated for this case. We hypothesize that the highly elevated SF6 levels above Kitt Peak resulted from a local release experiment rather than production via electrochemical fluoridation of intermediate products, the proposed source of atmospheric SF5CF3. The absence of the SF5CF3 feature in the spectra with elevated SF6 is consistent with the absence of SF5CF3 reported in a pure SF6 sample. Published by Elsevier Science Ltd.

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See detailControlled substances and other source gases, Chapter 1 of the Scientific Assessment of Ozone Depletion: 2002
Montzka, S. A.; Fraser, P. J.; Butler, J. H.; Cunnold, D. M.; Daniel, J. S.; Derwent, R. G.; Lal, S.; McCulloch, A.; Oram, D. E.; Reeves, C. E.; Sanhueza, E.; Steele, L. P.; Velders, G. J. M.; Weiss, R. F.; Zander, Rodolphe; Andersen, S. O.; Anderson, John; Blake, D. R.; Chipperfield, Martyn P.; Dlugokencky, E.; Elkins, James W.; Engel, Andreas; Harper, D.; Mahieu, Emmanuel; Pfeilsticker, K.; Pommereau, Jean-Pierre; Russell III, Jim M.; Taylor, G.; Van Roozendael, Michel; Waugh, D. W.

in Nohende Ajavon, Ayité-Lô; Albritton, Daniel L.; Mégie, Gérard; Watson, Robert (Eds.) Scientific Assessment of Ozone Depletion: 2002 (2003)

This chapter provides an update on scientific progress since the previous Scientific Assessment of Ozone Depletion (WMO, 1999) regarding ozone-depleting substances (ODSs) in the atmosphere. This includes a discussion of the latest available data for observed trends in the troposphere and stratosphere, emissions, lifetimes, Ozone Depletion Potentials (ODPs), and Global Warming Potentials (GWPs). On the basis of this updated informaion, we relate observations of ODSs in the atmosphere to expectations, and discuss the evidence that the Montreal Protocol is effectively reducing ozone-depleting gases in the atmosphere.

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See detailRetrieval and characterization of ozone profiles from solar infrared spectra at the Jungfraujoch
Barret, B.; De Maziere, M.; Demoulin, Philippe

in Journal of Geophysical Research. Atmospheres (2002), 107(D24),

[1] Vertical distributions of ozone from June 1996 to November 2000 have been retrieved from high-resolution Fourier transform infrared (FTIR) solar absorption spectra recorded at the primary Network for Detection of Stratospheric Change station of the Jungfraujoch in the Swiss Alps (46.5degreesN, 8degreesE, 3580 m above sea level (asl). The retrievals were performed using the Optimal Estimation Method (OEM), both in a narrow spectral interval (1002.567-1003.2 cm(-1)) and in a broad spectral interval (1000.0-1005.0 cm(-1)) in the O-3 9.6-mum band. A thorough characterization of the retrievals has been performed following the lines of OEM, including an information content analysis, a study of the correlations between retrieved instrumental parameters and retrieved ozone concentrations, and an evaluation of the O-3 profile error budget. It is demonstrated that the information content is significantly higher for spectra in the broad microwindow, resulting in higher vertical resolutions, on the order of 8 km, of the retrieved profiles extending up to 40 km, and less correlations between retrieved parameters. An independent statistical verification of the retrieval results and their characterization has been performed by comparison of the FTIR ozone profiles with independent measurements. These are the ozone profile measurements from balloon soundings at Payerne, from the microwave radiometer at Bern and the lidar at Observatoire de Haute-Provence (OHP), and the total column data from the Dobson spectrophotometer at Arosa. Applying the optimum retrieval procedure in the broad spectral interval, an excellent agreement has been found between the FTIR O-3 profile data and the correlative data. The largest offset of the FTIR data in comparison with the correlative data is found with respect to the lidar data in the 24- to 40-km layer, and is on the order of 5%. No systematic biases have been found in the troposphere, neither in the upper troposphere-lower stratosphere (UTLS) up to 18 km. The dispersion of the relative differences between the data sets, if any, is never larger than half of the natural ozone variability.

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See detailAtmospheric Trace Molecule Spectroscopy (ATMOS) experiment version 3 data retrievals
Irion, Fredrick W.; Gunson, Michael R.; Toon, Geoff C.; Chang, Albert Y.; Eldering, Annmarie; Mahieu, Emmanuel; Manney, Gloria L.; Michelsen, Hope A.; Moyer, Elizabeth J.; Newchurch, Michael J.; Osterman, Gregory B.; Rinsland, Curtis P.; Salawitch, Ross J.; Sen, Bhaswar; Yung, Yuk L.; Zander, Rodolphe

in Applied Optics (2002), 41(33), 6968-6979

Version 3 of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment data set for some 30 trace and minor gas profiles is available. From the IR solar-absorption spectra measured during four Space Shuttle missions (in 1985, 1992, 1993, and 1994), profiles from more than 350 occultations were retrieved from the upper troposphere to the lower mesosphere. Previous results were unreliable for tropospheric retrievals, but with a new global-fitting algorithm profiles are reliably returned down to altitudes as low as 6.5 km (clouds permitting) and include notably improved retrievals of H2O, CO, and other species. Results for stratospheric water are more consistent across the ATMOS spectral filters and do not indicate a net consumption of H-2 in the upper stratosphere. A new sulfuric-acid aerosol product is described. An overview of ATMOS Version 3 processing is presented with a discussion of estimated uncertainties. Differences between these Version 3 and previously reported Version 2 ATMOS results are discussed. Retrievals are available at http://atmos.jpl.nasa.gov/atmos. (C) 2002 Optical Society of America.

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See detailGround-based infrared spectroscopic measurements of carbonyl sulfide: Free tropospheric trends from a 24-year time series of solar absorption measurements
Rinsland, Curtis P.; Goldman, Aaron; Mahieu, Emmanuel; Zander, Rodolphe; Notholt, Justus; Jones, Nicholas B.; Griffith, D. W. T.; Stephen, T. M.; Chiou, L. S.

in Journal of Geophysical Research. Atmospheres (2002), 107(D22),

[1] Solar absorption spectra recorded over a 24-year time span have been analyzed to retrieve average free tropospheric mixing ratios of carbonyl sulfide (OCS). The measurements were recorded with the Fourier transform spectrometer located in the U. S. National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.09 km, lat. 31.9degreesN, long. 111.6degreesW), southwest of Tucson, Arizona, and were obtained on 167 days between May 1978 and February 2002, typically at 0.01-cm(-1) spectral resolution. A best fit to the time series shows an average mixing ratio of 566 pptv (1 pptv = 10(-12) per unit volume) between 2.09 and 10 km, a small but statistically significant long-term decrease equal to (-0.25 +/- 0.04)% yr(-1), 1 sigma, and a seasonal variation with a summer maximum, a winter minimum, and a peak amplitude of (1.3 +/- 0.4)%, 1 sigma, relative to the mean. Although a statistically significant decline and seasonal variation have been detected, both are exceedingly small. The present results confirm and extend earlier studies showing that the OCS free tropospheric abundance at northern midlatitudes has remained nearly constant over the last decades.

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See detailStratospheric HF column abundances above Kitt Peak (31.9 degrees N latitude): trends from 1977 to 2001 and correlations with stratospheric HCl columns
Rinsland, Curtis P.; Zander, Rodolphe; Mahieu, Emmanuel; Chiou, Linda S.; Goldman, Aharon; Jones, Nicholas B.

in Journal of Quantitative Spectroscopy and Radiative Transfer (2002), 74(2), 205-216

Time series of stratospheric hydrogen fluoride (HF) column abundances have been derived from infrared solar absorption spectra recorded for 195 days between May 1977 and June 2001 at a spectral resolution of typically 0.01 cm(-1). The measurements were made at the US National Solar Observatory facility on Kitt Peak, Arizona, USA (31.9degreesN, 111.6degreesW, 2.09 km altitude) and have been analyzed with the SFIT2 algorithm, which is based on a semi-empirical application of the optimal estimation method. The measurements show a continuous buildup of the stratospheric HF column over the 24-yr period superimposed on short-term variations and a seasonal cycle with spring maxima and autumn minima. The measured stratospheric HF columns increased by a factor of 4.7, from 2.03 x 10(14) molecule cm(-2) in May 1977 to 9.49 x 10(14) molecule cm(-2) in June 2001. A best fit with a model that assumes an exponential increase in the stratospheric HF column with time superimposed on a sinusoidal seasonal cycle yields an average rate of stratospheric HF column increase of (4.30 +/- 0.15% yr(-1)), 1 sigma. The rate of increase is nearly a factor of two less than that derived previously from 1977 to 1990 Kitt Peak total columns, which indicates a significant slowdown in the increase rate during the 1990s, consistent with the trends from recent near-global lower mesospheric satellite remote and surface in situ measurements. Day-to-day stratospheric HIT columns are highly correlated with the same day stratospheric HCl columns as a result of common transport of lower and higher latitude air to above the station. Extrapolation of the linear relation between the two sets of stratospheric columns indicates a background HCl column of 1 x 10(15) molecule cm(-2) for zero HF, consistent with a previous estimate from 1977 to 1990 HF and HCl Kitt Peak total column measurements and a 1973 HCl measurement above the station. (C) 2002 Elsevier Science Ltd. All rights reserved.

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See detailMultiyear infrared solar spectroscopic measurements of HCN, CO, C2H6,and C2H2 tropospheric columns above Lauder, New Zealand (45 degrees S latitude)
Rinsland, Curtis P.; Jones, Nicholas B.; Connor, Brian J.; Wood, Stephen W.; Goldman, Aaron; Stephen, Thomas M.; Murcray, Frank J.; Chiou, Linda S.; Zander, Rodolphe; Mahieu, Emmanuel

in Journal of Geophysical Research. Atmospheres (2002), 107(D14),

[1] Near-simultaneous, 0.0035 or 0.007 cm(-1) resolution infrared solar absorption spectra of tropospheric HCN, C2H2, CO, and C2H6 have been recorded from the Network for the Detection of Stratospheric Change station in Lauder, New Zealand (45.04degreesS, 169.68degreesE, 0.37 km altitude). All four molecules were measured on over 350 days with HCN and C2H2 reported for the first time based on a new analysis procedure that significantly increases the effective signal-to-noise of weak tropospheric absorption features in the measured spectra. The CO measurements extend by 2.5 years a database of measurements begun in January 1994 for CO with improved sensitivity in the lower and middle troposphere. The C2H6 measurements lengthen a time series begun in July 1993 with peak sensitivity in the upper troposphere. Retrievals of all four molecules were obtained with an algorithm based on the semiempirical application of the Rodgers optimal estimation technique. Columns are reported for the 0.37- to 12-km-altitude region, approximately the troposphere above the station. The seasonal cycles of all four molecules are asymmetric, with minima in March-June and sharp peaks and increased variability during August-November, which corresponds to the period of maximum biomass burning near the end of the Southern Hemisphere tropical dry season. Except for a possible HCN column decrease, no evidence was found for a statistically significant long-term trend.

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See detailATMOS version 3 water vapor measurements: Comparisons with observations from two ER-2 Lyman-alpha hygrometers, MkIV, HALOE, SAGE II, MAS, and MLS
Michelsen, Hope A.; Manney, Gloria L.; Irion, Fredrick W.; Toon, Geoff C.; Gunson, Michael R.; Rinsland, Curtis P.; Zander, Rodolphe; Mahieu, Emmanuel; Newchurch, Michael J.; Purcell, P. N.; Remsberg, E. E.; Russell, J. M.; Pumphrey, H. C.; Waters, J. W.; Bevilacqua, Richard M.; Kelly, K. K.; Hintsa, E. J.; Weinstock, E. M.; Chiou, E. W.; Chu, W. P.; McCormick, M. P.; Webster, C. R.

in Journal of Geophysical Research. Atmospheres (2002), 107(D3),

[1] We have compared a new version of Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS) retrievals (version 3) of stratospheric and mesospheric water vapor with observations from shuttleborne, satelliteborne, balloonborne, and aircraftborne instruments. These retrievals show agreement to within 5% with the MkIV observations in the middle and lower stratosphere. ATMOS agrees with the National Oceanic and Atmospheric Administration (NOAA) Lyman-alpha hygrometer to within 5% except for features with spatial scales less than the vertical resolution of ATMOS (such as the lower stratospheric seasonal cycle). ATMOS observations are 10-16% lower than measurements from the Harvard Lyman-alpha hygrometer in the lower stratosphere and are 7-14% higher than those from the Microwave Limb Sounder (MLS; prototype version 0104) throughout most of the stratosphere. Agreement is within 7% with the Millimeter-Wave Atmospheric Sounder (MAS; version 20) in the middle and upper stratosphere, but differences are closer to 13% in the lower stratosphere. Throughout the stratosphere, agreement is within 8% with the Halogen Occultation Experiment (HALOE; version 19). ATMOS data from 1994 show agreement with the Stratospheric Aerosol and Gas Experiment II (SAGE II; version 6) values to within 8% in the middle stratosphere, but ATMOS observations are systematically higher than those from SAGE II by as much as 41% in the lower stratosphere. In contrast, ATMOS 1985 values are systematically similar to50% lower than SAGE II values from sunset occultations in the lower stratosphere near 70 hPa but appear to be in better agreement with sunrise occultations. Version 3 retrievals in the upper stratosphere and lower mesosphere are typically 5-10% lower than version 2 values between 1 and 0.05 hPa. This reduction improves agreement with HALOE, MAS, and MLS upper atmospheric observations, but ATMOS values still tend to be higher than values from these instruments in the middle mesosphere. Agreement among the instruments compared here (except for SAGE II) is generally within 15% in the middle to lower stratosphere and mesosphere and within 10% in the middle to upper stratosphere. At altitudes near 30 km, all instruments (including SAGE II) agree to within 10%.

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See detailEnhanced tropospheric HCN columns above Kitt Peak during the 1982-1983 and 1997-1998 El Nino warm phases
Rinsland, Curtis P.; Goldman, Aaron; Zander, Rodolphe; Mahieu, Emmanuel

in Journal of Quantitative Spectroscopy and Radiative Transfer (2001), 69(1), 3-8

Free tropospheric HCN columns have been derived from infrared solar spectra recorded with the National Solar Observatory Fourier transform spectrometer on Kitt Peak, Arizona (31.9ºN latitude, 111.6ºW longitude, 2.09 km altitude) between May 1978 and May 2000. The time series show up to a factor of 2.4 enhancement during the strong El Ninos of 1982-1983 and 1997-1998, the most intense since 1970. The observations provide confirmation that HCN is a sensitive tracer of biomass burning emissions transported to the free troposphere. No statistically significant long-term trend in the HCN-free tropospheric column has been detected over the 22-year measurement period. The results illustrate the importance of long-term spectroscopic measurements for quantifying climate and atmospheric chemistry-related atmospheric changes.

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See detailFree tropospheric CO, C2H6, and HCN above central Europe: Recent measurements from the Jungfraujoch station including the detection of elevated columns during 1998
Rinsland, C. P.; Mahieu, Emmanuel; Zander, Rodolphe; Demoulin, Philippe; Forrer, J.; Buchmann, B.

in Journal of Geophysical Research. Atmospheres (2000), 105(D19), 24235-24249

Time series of free tropospheric carbon monoxide (CO), ethane (C2H6), and hydrogen cyanide (HCN) column abundances have been derived from observations at the International Scientific Station of the Jungfraujoch (ISSJ) at 3.58-km altitude in the Swiss Alps (latitude 46.55 degreesN, 7.98 degreesE longitude). The free troposphere was assumed to extend from 3.58 to 11 km altitude, and the related columns were derived for all three molecules from high spectral resolution infrared solar spectra recorded between January 1995 and October 1999. The three molecules show distinct seasonal cycles with maxima during winter for CO and C2H6, and during spring for HCN. These seasonal changes are superimposed on interannual variations. The tropospheric columns of all three molecules were elevated during 1998. Increases were most pronounced for HCN with enhanced values throughout the year, up to a factor of 2 in January 1998 when compared to averages of the other years. The increased tropospheric columns coincide with the period of widespread wildfires during the strong El Nino warm phase of 1997-1998. The emission enhancements above ISSJ are less pronounced, and they peaked after the increases measured above Mauna Loa (19.55 degreesN, 155.6 degreesW). Tropospheric trends for CO, C2H6, and HCN of (2.40 +/- 0.49), (0.47 +/- 0.64), and (7.00 +/- 1.61)% yr(-1)(1 sigma) were derived for January 1995 to October 1999. However, if 1998 measurements are excluded from the fit, CO and HCN trends that are not statistically significant, and a statistically significant decrease in the C2H6 tropospheric column, are inferred. Comparisons of the infrared CO columns with CO in situ surface measurements suggest that the CO free tropospheric vertical Volume mixing ratio profile generally decreases with altitude throughout the year.

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See detailModeled and empirical approaches for retrieving columnar water vapor from solar transmittance measurements in the 0.72, 0.82, and 0.94 μm absorption bands
Ingold, T.; Schmid, B.; Mätzler, C.; Demoulin, Philippe; Kämpfer, N.

in Journal of Geophysical Research (2000), 105(D19), 2432724343

A Sun photometer (18 channels between 300 and 1024 nm) has been used for measuring the columnar content of atmospheric water vapor (CWV) by solar transmittance measurements in absorption bands with channels centered at 719, 817, and 946 nm. The observable is the band-weighted transmittance function defined by the spectral absorption of water vapor and the spectral features of solar irradiance and system response. The transmittance function is approximated by a three-parameter model. Its parameters are determined from MODTRAN and LBLRTM simulations or empirical approaches using CWV data of a dual-channel microwave radiometer (MWR) or a Fourier transform spectrometer (FTS). Data acquired over a 2-year period during 1996–1998 at two different sites in Switzerland, Bern (560 m above sea level (asl)) and Jungfraujoch (3580 m asl) were compared to MWR, radiosonde (RS), and FTS retrievals. At the low-altitude station with an average CWV amount of 15 mm the LBLRTM approach (based on recently corrected line intensities) leads to negligible biases at 719 and 946 nm if compared to an average of MWR, RS, and GPS retrievals. However, at 817 nm an overestimate of 2.7 to 4.3 mm (18–29%) remains. At the high-altitude station with an average CWV amount of 1.4 mm the LBLRTM approaches overestimate the CWV by 1.0, 1.4, and 0.1 mm (58, 76, and 3%) at 719, 817, and 946 nm, compared to the FTS instrument. At the low-altitude station, CWV estimates, based on empirical approaches, agree with the MWR within 0.4 mm (2.5% of the mean); at the high-altitude site with a factor of 10 less water vapor the agreement of the SPM with the FTS is 0.0 to 0.2 mm (1 to 9% of the mean CWV there). Sensitivity analyses show that for the conditions met at the two stations with CWV ranging from 0.2 to 30 mm, the retrieval errors are smallest if the 946 nm channel is used.

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See detailCorrelation relationships of stratospheric molecular constituents from high spectral resolution, ground-based infrared solar absorption spectra
Rinsland, C. P.; Goldman, A.; Connor, B. J.; Stephen, T. M.; Jones, N. B.; Wood, S. W.; Murcray, F. J.; David, S. J.; Blatherwick, R. D.; Zander, Rodolphe; Mahieu, Emmanuel; Demoulin, Philippe

in Journal of Geophysical Research. Atmospheres (2000), 105(D11), 14637-14652

Comparisons of chemically active species with chemically inert tracers are useful to quantify transport and mixing and assess the accuracy of model predictions. We report measurements of chemically active species and chemically inert tracers in the stratosphere derived from the analysis of infrared solar absorption spectra recorded with a ground-based Fourier transform spectrometer operated typically at 0.005- to 0.01-cm(-1) spectral resolution. The measurements were recorded from Kitt Peak in southern Arizona (latitude 31.9 degrees N, 111.6 degrees W, 2.09 km altitude). Time series of N2O, CH4, O3, and HNO3 vertical profiles have been retrieved from measurements in microwindows. From these results, correlations between N2O and CH4 stratospheric mixing ratios and between O3 and HNO3 lower stratospheric mixing ratios have been derived. The measured correlations between N2O versus CH4 mixing ratios are compact and show little variability with respect to season in quantitative agreement with Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS) spring and autumn measurements recorded near the same latitude. Lower stratospheric O3 versus HNO3 mixing ratios measured during low to moderate aerosol loading time periods also show a compact relations though the HNO3/O3 slope is a factor of 2 lower than obtained from November 1994 ATMOS measurements near the Same latitude. We also compare Kitt Peak and ATMOS N2O versus CH4 and O3 versus HNO3 relations obtained by averaging the measurements over two broad stratospheric layers. This comparison avoids bias from the a priori profiles and the limited vertical resolution of the ground-based observations.

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See detailStratospheric CO at tropical and mid-latitudes: ATMOS measurements and photochemical steady-state model calculations
Rinsland, C. P.; Salawitch, R. J.; Osterman, G. B.; Irion, F. W.; Sen, B.; Zander, Rodolphe; Mahieu, Emmanuel; Gunson, M. R.

in Geophysical Research Letters (2000), 27(9), 1395-1398

We characterize the spring and fall stratospheric distribution of CO at 49 degrees N-55 degrees S latitude from ATMOS profiles measured during 4 shuttle flights, Measured mixing ratios increase with potential temperature (theta) from 12 ppbv (10(-9) per unit volume) at 525 K, to 30-40 ppbv at 1750 K with only minor variations with latitude and season at a theta level. Evidence for some confinement near 1150 K in the developing November 1994 vortex is indicated from comparison of CO and N2O horizontal gradients. Measured CO mixing ratios at the tropical tropopause are a factor of 10 higher than values calculated with a steady-state model using standard photochemistry constrained by correlative temperatures and pressures, and ATMOS measurements including CH4 as inputs, Differences decrease with latitude at constant theta and are <20% at 800 K and all latitudes, where the CO photochemical lifetime is 40-50 days.

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See detailPolar stratospheric descent of NOy and CO and Arctic denitrification during winter 1992-1993
Rinsland, C. P.; Salawitch, R. J.; Gunson, M. R.; Solomon, S.; Zander, Rodolphe; Mahieu, Emmanuel; Goldman, A.; Newchurch, M. J.; Irion, F. W.; Chang, A. Y.

in Journal of Geophysical Research. Atmospheres (1999), 104(D1), 1847-1861

Observations inside the November 1994 Antarctic stratospheric vortex and inside the April 1993 remnant Arctic stratospheric vortex by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer are reported. In both instances, elevated volume mixing ratios (VMRs) of carbon monoxide (CO) were measured. A peak Antarctic CO VMR of 60 ppbv (where 1 ppbv = 10(-9) per unit volume) was measured at a potential temperature (Theta) of 710 K (similar to 27 km), about 1 km below the altitude of a pocket of elevated NOy (total reactive nitrogen) at a deep minimum in N2O (<5 ppbv). The Arctic observations also show a region of elevated vortex CO with a peak VMR of 90 ppbv at 630-670 K (similar to 25 km) but no corresponding enhancement in NOy, perhaps because of stronger dynamical activity in the northern hemisphere polar winter and/or interannual variability in the production of mesospheric NO. By comparing vortex and extravortex observations of NOy obtained at the same N2O VMR, Arctic vortex denitrification of 5 +/- 2 ppbv at 470 K (similar to 18 km) is inferred. We show that our conclusion of substantial Arctic winter 1992-1993 denitrification is robust by comparing our extravortex observations with previous polar measurements obtained over a wide range of winter conditions. Correlations of NOy with N2O measured at the same Theta by ATMOS in the Arctic vortex and at midlatitudes on board the ER-2 aircraft several weeks later lie along the same mixing line. The result demonstrates the consistency of the two data sets and confirms that the ER-2 sampled fragments of the denitrified Arctic vortex following its breakup, An analysis of the ATMOS Arctic measurements of total hydrogen shows no evidence for significant dehydration inside the vortex.

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See detailQuantitative evaluation of the post-Mount Pinatubo NO2 reduction and recovery, based on 10 years of Fourier transform infrared and UV-visible spectroscopic measurements at Jungfraujoch
De Mazière, Martine; Van Roozendael, Michel; Hermans, Christian; Simon, Paul C.; Demoulin, Philippe; Roland, Ginette; Zander, Rodolphe

in Journal of Geophysical Research (1998), 103(D9), 10849-10858

The colocation of two technically different instruments for ground-based remote sensing of NO2 total column amounts at the primary Network for the Detection of Stratospheric Change Alpine station of the Jungfraujoch (46.5°N, 8.0°E) has been exploited for mutual validation of the long-term NO2 time series from both instruments and for a quantitative evaluation of the impact of the Mount Pinatubo eruption on the NO2 abundance above this northern mid-latitude observatory. The two techniques are high-resolution Fourier transform infrared solar absorption spectrometry and zenith-sky differential optical absorption spectroscopy in the UV visible. The diurnal variation of NO2 has been simulated by a simple photochemical model that allows a comparison between the data from the two techniques. This model is shown to reproduce the observed morning to evening ratios to 2.3%, on average, which is fully adequate for the needs of this study. From the 1985–1996 combined time series of NO2 morning and evening abundances, it has been concluded that the enhanced aerosol load injected into the stratosphere by Mount Pinatubo caused a maximum NO2 reduction above the Jungfraujoch by 45% in early January 1992 that died out quasi-exponentially to zero by the beginning of 1995.

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See detailVertical column abundances of COF2 above the Jungfraujoch Station, derived from ground-based infrared solar observations
Mélen, F.; Mahieu, Emmanuel; Zander, Rodolphe; Rinsland, C. P.; Demoulin, Philippe; Roland, Ginette; Delbouille, Luc; Servais, Christian

in Journal of Atmospheric Chemistry (1998), 29(2), 119-134

Total vertical column abundances of carbonyl fluoride (COF2) have been derived from observations made at the International Scientific Station of the Jungfraujoch (ISSJ; altitude 3.58 km, latitude 46.5 degrees N, longitude 8.0 degrees E), Switzerland. A systematic analysis of two microwindows containing lines of the vi band was performed, based on a large set of high resolution infrared solar absorption spectra recorded with Fourier transform spectrometers, from 1985 to 1995. Examination of the whole available database indicates a significant increase of the burden of COF2 during the 1988-1995 period. The average exponential rate and the average linear rate referenced to 1992, calculated from daily mean measurements, are both equal to (4.0 +/- 0.5)% yr(-1) (one sigma error). The results are also evaluated and discussed within the context of seasonal variability and correlation between carbonyl fluoride and hydrogen fluoride (HF) columns above the ISSJ.

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See detailNorthern and southern hemisphere ground-based infrared spectroscopic measurements of tropospheric carbon monoxide and ethane
Rinsland, C. P.; Jones, N. B.; Connor, B. J.; Logan, J. A.; Pougatchev, N. S.; Goldman, A.; Murcray, F. J.; Stephen, T. M.; Pine, A. S.; Zander, Rodolphe; Mahieu, Emmanuel; Demoulin, Philippe

in Journal of Geophysical Research. Atmospheres (1998), 103(D21), 28197-28217

Time series of CO and C2H6 measurements have been derived from high-resolution infrared solar spectra recorded in Lauder, New Zealand (45.0 degrees S, 169.7 degrees E, altitude 0.37 km), and at the U.S. National Solar Observatory (31.9 degrees N, 111.6 degrees W, altitude 2.09 km) on Kitt Peak. Lauder observations were obtained between July 1993 and November 1997, while the Kitt Peak measurements were recorded between May 1977 and December 1997. Both databases were analyzed with spectroscopic parameters that included significant improvements for C2H6 relative to previous studies. Target CO and C2H6 lines were selected to achieve similar vertical samplings based on averaging kernels. These calculations show that partial columns from layers extending from the surface to the mean tropopause and from the mean tropopause to 100 km are nearly independent. Retrievals based on a semiempirical application of the Rodgers optimal estimation technique are reported for the lower laver, which has a broad maximum in sensitivity in the upper troposphere. The Lauder CO and C2H6 partial columns exhibit highly asymmetrical seasonal cycles with minima in austral autumn and sharp peaks in austral spring. The spring maxima are the result of tropical biomass burning emissions followed by deep convective vertical transport to the upper troposphere and long-range horizontal transport. Significant year-to-year variations are observed for both CO and C2H6, but the measured trends, (+0.37 +/- 0.57)% yr(-1) and (-0.64 +/- 0.79)% yr(-1), 1 sigma, respectively, indicate no significant long-term changes. The Kitt Peak data also exhibit CO and C2H6 seasonal variations in the lower layer with trends equal to (-0.27 +/- 0.17)% yr(-1) and (-1.20 +/- 0.35')% yr(-1), 1 sigma, respectively. Hence a decrease in the Kitt Peak tropospheric C2H6 column has been detected, though the CO trend is not significant. Both measurement sets are compared with previous observations, reported trends, and three-dimensional model calculations.

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See detailGround-based infrared solar spectroscopic measurements of carbon monoxide during 1994 Measurement of Air Pollution From Space flights
Pougatchev, N. S.; Jones, N. B.; Connor, B. J.; Rinsland, C. P.; Becker, E.; Coffey, M. T.; Connors, V. S.; Demoulin, Philippe; Dzhola, A. V.; Fast, H.; Grechko, E. I.; Hannigan, J. W.; Koike, M.; Kondo, Y.; Mahieu, Emmanuel; Mankin, W. G.; Mittermeier, R. L.; Notholt, J.; Reichle, H. G.; Sen, B.; Steele, L. P.; Toon, G. C.; Yurganov, L. N.; Zander, Rodolphe; Zhao, Y.

in Journal of Geophysical Research. Atmospheres (1998), 103(D15), 19317-19325

Results of the comparison of carbon monoxide ground-based infrared solar spectroscopic measurements with data obtained during 1994 Measurement of Air Pollution From Space (MAPS) flights are presented. Spectroscopic measurements were performed correlatively with April and October MAPS flights by nine research groups from Belgium, Canada, Germany, Japan, New Zealand, Russia, and the United States. Characterization of the techniques and error analysis were performed. The role of the CO a priori profile used in the retrieval was estimated. In most cases an agreement between spectroscopic and MAPS data is within estimated MAPS accuracy of +/-10%.

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See detailATMOS/ATLAS 3 infrared profile measurements of trace gases in the November 1994 tropical and subtropical upper troposphere
Rinsland, C. P.; Gunson, M. R.; Wang, P.-H.; Arduini, R. F.; Baum, B. A.; Minnis, P.; Goldman, A.; Abrams, M. C.; Zander, Rodolphe; Mahieu, Emmanuel; Salawitch, R. J.; Michelsen, H. A.; Irion, F. W.; Newchurch, M. J.

in Journal of Quantitative Spectroscopy and Radiative Transfer (1998), 60(5), 891-901

Vertical mixing ratio profiles of four relatively long-lives gases, HCN, C2H2, CO, and C2H6, have been retrieved from 0.01 cm(-1) resolution infrared solar occultation spectra recorded between latitudes of 5.3 degrees N and 31.4 degrees N. The observations were obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Science (ATLAS) 3 shuttle flight, 3-12 November 1994. Elevated mixing ratios below the tropopause were measured for these gases during several of the occultations. The positive correlations obtained between the simultaneously measured mixing ratios suggest that the enhancements are likely the result of surface emissions, most likely biomass burning and/or urban industrial activities, followed by common injection via deep convective transport of the gases to the upper troposphere. The elevated levels of HCN may account for at least part of the "missing NOy" in the upper troposphere. Comparisons of the observations with values measured during a recent aircraft campaign are presented. Published by Elsevier Science Ltd.

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See detailATMOS/ATLAS 3 infrared profile measurements of clouds in the tropical and subtropical upper troposphere
Rinsland, C. P.; Gunson, M. R.; Wang, P.-H.; Arduini, R. F.; Baum, B. A.; Minnis, P.; Goldman, A.; Abrams, M. C.; Zander, Rodolphe; Mahieu, Emmanuel; Salawitch, R. J.; Michelsen, H. A.; Irion, F. W.; Newchurch, M. J.

in Journal of Quantitative Spectroscopy and Radiative Transfer (1998), 60(5), 903-919

Vertical profiles of infrared cirrus extinction have been derived from tropical and subtropical upper tropospheric solar occultation spectra. The measurements were recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Sciences (ATLAS) 3 shuttle flight in November 1994. The presence of large numbers of small ice crystals is inferred from the appearance of broad extinction features in the 8-12 mu m region. These features were observed near the tropopause and at lower altitudes. Vertical profiles of the ice extinction (km(-1)) in microwindows at 831, 957, and 1204 cm(-1) have been retrieved from the spectra and analyzed with a model for randomly oriented spheroidal ice crystals. An area-equivalent spherical radius of 6 mu m is estimated from the smallest ice crystals observed in the 8-12 mu m region. Direct penetration of clouds into the lower stratosphere is inferred from observations of cloud extinction extending from the upper troposphere to 50 mbar (20 km altitude). Cloud extinction between 3 and 5 mu m shows very little wavelength dependence, at least for the cases observed by the ATMOS instrument in the tropics and subtropics during ATLAS 3. Published by Elsevier Science Ltd.

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See detailCorrelations of stratospheric abundances of NOy, O3, N2O, and CH4 derived from ATMOS measurements
Michelsen, H. A.; Manney, G. L.; Gunson, M. R.; Zander, Rodolphe

in Journal of Geophysical Research. Atmospheres (1998), 103(D21), 28347--28359

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See detailCorrelations of stratospheric abundances of CH4 and N2O derived from ATMOS measurements
Michelsen, H. A.; Manney, G. L.; Gunson, M. R.; Rinsland, C. P.; Zander, Rodolphe

in Geophysical Research Letters (1998), 25(15), 2777--2780

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See detailObserved trends in total vertical column abundances of atmospheric gases from IR solar spectra recorded at the Jungfraujoch
Mahieu, Emmanuel; Zander, Rodolphe; Delbouille, Luc; Demoulin, Philippe; Roland, Ginette; Servais, Christian

in Journal of Atmospheric Chemistry (1997), 28(1-3), 227-243

Since 1984, about 15 000 high quality infrared solar spectra have been recorded with state-of-the-art grating and Fourier transform spectrometers at the International Scientific Station of the Jungfraujoch, Switzerland. Nonlinear least squares spectral curve fitting of selected microwindows containing isolated and well characterized lines of 20 telluric gases have allowed to retrieve their total vertical column abundances above the station, leading to observational data bases essential to derive long- and short-term changes experienced by these species during the last 12 years. In this paper, we focus on atmospheric gases of particular interest within the context of the EUROTRACTOR (Tropospheric Ozone Research) project; secular evolution as well as seasonal cycles of the minor constituents CH4, CO and of the trace gases C2H6, OCS, C2H2, HCN and H2CO are reported and discussed. The long-lived N2O is included as a tracer of the dynamic activity of the atmosphere.

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See detailRetrieval of ozone vertical column amounts from ground-based high resolution infrared solar spectra
Hamdouni, A.; Barbe, Alain; Demoulin, Philippe; Zander, Rodolphe

in Journal of Quantitative Spectroscopy and Radiative Transfer (1997), 57(1), 11-22

Good infrared spectral regions to retrieve accurately the vertical column amount of ozone from ground observations are proposed. Their selection was based on studies of the influence of spectroscopic (frequencies, half-widths, intensities) as well as geophysical parameters (volume mixing ratios, temperature profiles) with a particular attention for temperature. The results, obtained in three different spectral regions, with a realistic T-profile are very consistent.

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See detailOn the use of HF as a reference for the comparison of stratospheric observations and models
Chipperfield, M. P.; Burton, M.; Bell, W.; Paton-Walsh, C.; Blumenstock, Thomas; Coffey, M. T.; Hannigan, J. W.; Mankin, W. G.; Galle, Bo; Mellqvist, Johan; Mahieu, Emmanuel; Zander, Rodolphe; Notholt, Justus; Sen, B.; Toon, G. C.

in Journal of Geophysical Research (1997), 102(11D), 12901-12919

Hydrogen fluoride (HF) is often used as a simple reference for other column observations of chemically active stratospheric species. However, seasonal and shorter timescale variations in column HF make its use as a reference more complicated. In this paper we characterize the expected magnitude of these variations in HF, and variations of ratio quantities involving HF, using a two-dimensional (2-D) photochemical model and two versions of a three-dimensional (3-D) transport model. The 2-D model predicts that the column ratios HNO3/HF and HCl/HF increase from midlatitudes to the tropics, although this is very sensitive to HCl and HNO3 abundances in the tropical upper troposphere. Seasonal variations in vertical motion modifys the predicted ratios; for example, wintertime descent at high latitudes decreases HCl/HF. The ratio HNO3/HF at high latitudes is strongly modified by seasonal variations in the chemical partitioning of the odd nitrogen (NOy) species. We compare these model predictions with ground-based Fourier transform infrared spectroscopy (FTIR) observations of HF along with HCl, ClONO2 and HNO3 obtained at eight northern hemisphere sites between October 1994 and July 1995. We investigate quantitatively how HF can be used as a tracer to follow the evolution of observations at a single station and to intercompare results from different stations or with photochemical models. The magnitude of the 3-D model HF column agrees well with the observations, except on some occasions at high latitudes, giving indirect support for the important role of COF2 in the stratospheric inorganic fluorine budget. The observed day-to-day variability in the column ratios HCl/HF and HNO3/HF is much larger at high latitudes. This variability is reproduced in the 3-D models and is due to horizontal motion. Short timescale vertical displacement of the species profiles is estimated to have a small effect on the column ratios. In particular, we analyze the usefulness of the observed column ratio (ClONO2 + HCl)/HF as an indicator for chlorine activation. Current measurement uncertainties limit the degree of activation which can be unambiguously detected using this observed quantity, but we can determine that chlorine-activated air was observed above Aberdeen (58 degrees N) on 6 days in late January 1995.

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See detailIncrease of stratospheric carbon tetrafluoride (CF4) based on ATMOS observations from space
Zander, Rodolphe; Solomon, S.; Mahieu, Emmanuel; Goldman, A.; Rinsland, C. P.; Gunson, M. R.; Abrams, M. C.; Chang, A. Y.; Salawitch, R. J.; Michelsen, H. A.; Newchurch, M. J.; Stiller, G. P.

in Geophysical Research Letters (1996), 23(17), 2353-2356

Stratospheric volume mixing ratio profiles of carbon tetrafluoride, CF4, obtained with the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during the ATLAS (Atmospheric Laboratory for Applications and Science) -3 mission of 1994 are reported. Overall the profiles are nearly constant over the altitude range 20 to 50 km, indicative of the very long lifetime of CF4 in the atmosphere. In comparison to the stratospheric values of CF4 inferred from the ATMOS/Spacelab 3 mission of 1985, the 1994 concentrations are consistent with an exponential increase of (1.6 +/- 0.6)%/yr. This increase is discussed with regard to previous results and likely sources of CF4 at the ground. Further, it is shown that simultaneous measurements of N2O and CF4 provide a means of constraining the lower limit of the atmospheric lifetime of CF4 at least 2,300 years, two sigma.

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See detailATMOS/ATLAS-3 measurements of stratospheric chlorine and reactive nitrogen partitioning inside and outside the November 1994 Antarctic vortex
Rinsland, Curtis P.; Gunson, Michael R.; Salawitch, R. J.; Michelsen, H. A.; Zander, Rodolphe; Newchurch, M. J.; Abbas, M. M.; Abrams, M. C.; Manney, Gloria L.; Chang, A. Y.; Irion, F. W.; Goldman, A.; Mahieu, Emmanuel

in Geophysical Research Letters (1996), 23(17), 2365-2368

Partitioning between HCl and ClONO2 and among the main components of the reactive nitrogen family (NO, NO2, HNO3, ClONO2, N2O5, and HO2NO2) has been studied inside and outside the Antarctic stratospheric vortex based on ATMOS profiles measured at sunrise during the 3-12 November 1994 ATLAS-3 Shuttle mission. Elevated mixing ratios of HCl in the lower stratosphere with a peak of similar to 2.9 ppbv (10(-9) parts per volume) were measured inside the vortex near 500 K potential temperature (similar to 19 km). Maximum ClONO2 mixing ratios of similar to 1.2, similar to 1.4, and similar to 0.9 ppbv near 700 K (similar to 25 km) were measured inside, at the edge, and outside the vortex, respectively. Model calculations reproduce the higher levels of HCl and NOx (NO + NO2) inside the lower stratospheric vortex both driven by photochemical processes initiated by low O3. The high HCl at low O3 results from chemical production of HCl via the reaction of enhanced Cl with CH4, limited production of ClONO2, and the descent of inorganic chlorine from higher altitudes.

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See detailThe 1994 northern midlatitude budget of stratospheric chlorine derived from ATMOS/ATLAS-3 observations
Zander, Rodolphe; Mahieu, Emmanuel; Gunson, M. R.; Abrams, M. C.; Chang, A. Y.; Abbas, M.; Aellig, C.; Engel, A.; Goldman, A.; Irion, F. W.; Kämpfer; Michelsen, H. A.; Newchurch, M. J.; Rinsland, C. P.; Salawitch, R. J.; Stiller, G. P.; Toon, G. C.

in Geophysical Research Letters (1996), 23(17), 2357-2360

Volume mixing ratio (VMR) profiles of the chlorine-bearing gases HCl, ClONO2, CCl3F, CCl2F2, CHClF2, CCl4, and CH3Cl have been measured between 3 and 49 degrees northern- and 65 to 72 degrees southern latitudes with the Atmospheric Trace MOlecule Spectroscopy (ATMOS) instrument during the ATmospheric Laboratory for Applications and Science (ATLAS)-3 shuttle mission of 3 to 12 November 1994. A subset of these profiles obtained between 20 and 49 degrees N at sunset, combined with ClO profiles measured by the Millimeter-wave Atmospheric Sounder (MAS) also from aboard ATLAS-3, measurements by balloon for HOCl, CH3CCl3 and C2Cl3F3, and model calculations for COClF indicates that the mean burden of chlorine, Cl-TOT, was equal to (3.53 +/- 0.10) ppbv (parts per billion by volume), 1-sigma, throughout the stratosphere at the time of the ATLAS 3 mission. This is some 37% larger than the mean 2.58 ppbv value measured by ATMOS within the same latitude zone during the Spacelab 3 flight of 29 April to 6 May 1985, consitent with an exponential growth rate of the chlorine loading in the stratosphere equal to 3.3%/yr or a linear increase of 0.10 ppbv/yr over the Spring-1985 to Fall-1994 time period. These findings are in agreement with both the burden and increase of the main anthropogenic Cl-bearing source gases at the surface during the 1980s, confirming that the stratospheric chlorine loading is primarily of anthropogenic origin.

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See detailComparison of modeled and empirical approaches for retrieving columnar water vapor from solar transmittance measurements in the 0.94 micrometer region
Schmid, B; Thome, K.J.; Demoulin, Philippe; Peter, R.; Mätzler, C.; Sekler, J.

in Journal of Geophysical Research (1996), 101

Four atmospheric transmittance models, LOWTRAN 7, MODTRAN 3, FASCOD3P, and the Thomason model, are investigated to quantify the relationship between water vapor transmittance as function of water vapor amount, Tw (U), for an instrument specific band pass in the 0.94-um region. In a second step an empirical Tw (U) function is established using long term measurements with our high-precision Sun photometer (SPM) in Bern, Switzerland along with 1300 simultaneous and collocated water vapor retrievals performed with a dual-channel microwave radiometer (MWR). In order to avoid a possible bias in the empirical Tw(U) function, the MWR data set is prescreened by comparing retrievals coincident with radiosonde ascents. Over a 2 1/2-year period of common observations, radiosondes and PM agreed to within 0.19 cm (13%) of columnar water vapor (CWV) using the empirical Tw (U) relationship. Completely independent comparisons with an additional MWR and two Fourier transform spectrometers yielded agreement within 13% and 9%, respectively. Comparing empirical and modeled results, we found that with respect to the experimental data, LOWTRAN 7, MODTRAN 3, and FASCOD3P reported higher water vapor transmittances over almost the entire range of realistic absorber amounts. By relating these differences to differences in retrieved CWV for the case of two standard atmospheres, we found that using Tw (U) predicted by LOWTRAN 7, MODTRAN 3, and FASCOD3P leads to an overestimate of CWV by about 18-30%, 7-20%, and 2-18%, respectively. The Thomason model yields good agreement with respect to the experimental data up to medium absorber amounts, whereas at slant path amounts larger than 10 cm, errors up to 60% in retrieved CWV occurred. We also show in this work that a misinterpretation of the LOWTRAN 7 water vapor output counterbalances incorrectly predicted Tw, leading to results that agree well with experimental ones

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See detailClONO2 total vertical column abundances above the Jungfraujoch Station, 1986-1994: Long-term trend and winter-spring enhancements
Rinsland, C. P.; Zander, Rodolphe; Demoulin, Philippe; Mahieu, Emmanuel

in Journal of Geophysical Research (1996), 101(D2), 3891-3899

Total vertical column abundances of chlorine nitrate (ClONO2) have been retrieved from 0.006 cm(-1) resolution solar absorption spectra recorded at the International Scientific Station of the Jungfraujoch (ISSJ) in the Swiss Alps (altitude 3.58 km, latitude 46.5 degrees N, longitude 8.0 degrees E) on 105 days between June 1986 and November 1994. The analysis is based on spectral fittings of the ClONO2 nu(4) band Q branch at 780.21 cm(-1) and the interferences occurring in the same spectral region. The ISSJ measurements show a regular long-term increase in the ClONO2 column with an occasional factor of 2 to 3 enhancements during the midwinter to early spring. Excluding data from this time of the year, the ISSJ database reflects a linear rate of increase and la uncertainty equal to (4.0 +/- 0.7)% yr(-1) referenced to 1990.0. The corresponding ClONO2 total vertical columns for mid-1986 and mid-1994 are equal to 0.92 and 1.26 x 10(15) molecules cm(-2), respectively. The high ClONO2 columns and high HF/HCl column ratios sometimes measured during winter indicate the occasional presence of chemically processed air above the station. This is corroborated by trajectories calculated for the stratospheric air masses sounded on these occasions.

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See detailTrends of OCS, HCN, SF6, CHClF2, (HCFC-22) in the lower stratosphere from 1985 and 1994 atmospheric trace molecule spectroscopy experiment measurements near 30 degrees N latitude
Rinsland, C. P.; Mahieu, Emmanuel; Zander, Rodolphe; Gunson, M. R.; Salawitch, R. J.; Chang, A. Y.; Goldman, A.; Abrams, M. C.; Abbas, M. M.; Newchurch, M. J.; Irion, F. W.

in Geophysical Research Letters (1996), 23(17), 2349-2352

Volume mixing ratio (VMR) profiles of OCS, HCN, SF6, and CHClF2 (HCFC-22) have been measured near 30 degrees N latitude by the Atmospheric Trace Molecule Spectroscopy Fourier transform spectrometer during shuttle flights on 29 April-6 May 1985 and 3-2 November 1994. The change in the concentration of each molecule in the lower stratosphere has been derived for this 9 1/2-year period by comparing measurements between potential temperatures of 395 to 800 K (similar to 17 to 30 km altitude) relative to simultaneously measured values of the long-lived tracer N2O. Exponential rates of increase inferred for 1985-to-1994 from these comparisons are (0.1 +/- 0.4)% yr(-1) for OCS, (1.0 +/- 1.0)% yr(-1) for HCN, (8.0+/-0.7)% yr(-1) for SF6, and (8.0 +/- 1.0)% yr(-1) for CHClF2 (HCFC-22), 1 sigma. The lack of an appreciable trend for OCS suggests the background (i.e., nonvolcanic) source of stratospheric aerosol was the same during the two periods. These results are compared with trends reported in the literature.

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See detailThe Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment: Deployment on the ATLAS Space Shuttle missions
Gunson, Michael R.; Abbas, M. M.; Abrams, M. C.; Allen, M.; Brown, L. R.; Brown, T. L.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Lowes, L. L.; Mahieu, Emmanuel; Manney, Gloria L.; Michelsen, H. A.; Newchurch, M. J.; Rinsland, C. P.; Salawitch, R. J.; Stiller, G. P.; Toon, G. C.; Yung, Y. L.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2333-2336

The ATMOS Fourier transform spectrometer was flown for a fourth time on the Space Shuttle as part of the ATLAS-3 instrument payload in November 1994. More than 190 sunrise and sunset occultation events provided measurements of more than 30 atmospheric trace gases at latitudes 3-49 degrees N and 65-72 degrees S, including observations both inside and outside the Antarctic polar vortex. The instrument configuration, data retrieval methodology, and mission background are described to place in context analyses of ATMOS data presented in this issue.

See detailRemote sensing of the Earth's atmosphere from space with high-resolution Fourier-transform spectroscopy: development and methodology of data processing for the Atmospheric Trace Molecule Spectroscopy experiment
Abrams, M. C.; Gunson, M. R.; Chang, A. Y.; Rinsland, C. P.; Zander, Rodolphe

in Applied Optics (1996), 35(16), 2774--2786

The methodology of spectroscopic remote sensing with high-resolution Fourier-transform spectra obtained from low Earth orbit by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment is discussed. During the course of the Atmospheric Laboratory for Applications and Science (ATLAS) shuttle missions(1992--1994) a flexible, yet reproducible, retrieval strategy was developed that culminated in the near-real-time processing of telemetry data into vertical profiles of atmospheric composition during the ATLAS-3 mission. The development,evolution, robustness, and validation of the measurements are presented and assessed with a summary comparison of trace-gas observations within the Antarctic polar vortex in November 1994.

See detailObservations of the infrared solar spectrum from space by the ATMOS experiment
Abrams, M. C.; Goldman, A.; Gunson, M. R.; Rinsland, C. P.; Zander, Rodolphe

in Applied Optics (1996), 35(16), 2747--2751

The final flight of the Atmospheric Trace Molecule Spectroscopy experiment as part of the Atmospheric Laboratory for Applications and Science (ATLAS-3) Space Shuttle mission in 1994 provided a new opportunity to measure broadband (625--4800 cm-1, 2.1--16 microns) infrared solar spectra at an unapodized resolution of 0.01 cm-1 from space. The majority of the observations were obtained as exoatmospheric, near Sun center, absorption spectra, which were later ratioed to grazing atmospheric measurements to compute the atmospheric transmission of the Earth's atmosphere and analyzed for vertical profiles of minor and trace gases. Relative to the SPACELAB-3 mission that produced 4800 high Sun spectra (which were averaged into four grand average spectra), the ATLAS-3 mission produced some 40,000 high Sun spectra (which have been similarly averaged) with an improvement in signal-to-noise ratio of a factor of 3--4 in the spectral region between 1000 and 4800 cm-1. A brief description of the spectral calibration and spectral quality is given as well as the location of electronic archives of these spectra.

See detailPressure sounding of the middle atmosphere from ATMOS solar occultationmeasurements of atmospheric CO2 absorption lines
Abrams, M. C.; Gunson, M. R.; Lowes, L. L.; Rinsland, C. P.; Zander, Rodolphe

in Applied Optics (1996), 35(16), 2810--2820

A method for retrieving the atmospheric pressure corresponding to the tangent pointof an infrared spectrum recorded in the solar occultation mode is described andapplied to measurements made by the Atmospheric Trace Molecule Spectroscopy (ATMOS)Fourier-transform spectrometer. Tangent pressure values are inferred frommeasurements of isolated CO2 lines with temperature-insensitive strengthsby measuring the slant-column CO2 amount and by adjusting the viewinggeometry until the calculated column matches the observed column. Tangent pressuresare determined with a spectroscopic precision of 1\%--3\%,corresponding to a tangent-point height precision of 70--210 m. The totaluncertainty is limited primarily by the quality of the spectra and ranges between4 and 6 (280--420 m) for spectra with signal-to-noise ratiosof 300:1 and between 4 and 10 for spectra with signal-to-noiseratios of 100:1. The retrieval of atmospheric pressure increases the accuracy of theretrieved-gas concentrations by minimizing the effect of systematic errors introducedby climatological pressure data, ephemeris parameters, and the uncertainties ininstrumental pointing.

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See detailATMOS measurements of H2O+2CH4 and total reactive nitrogen in the November 1994 Antarctic stratosphere: Dehydration and denitrification in the vortex
Rinsland, C. P.; Gunson, M. R.; Salawitch, R. J.; Newchurch, M. J.; Zander, Rodolphe; Abbas, M. M.; Abrams, M. C.; Manney, G. L.; Michelsen, H. A.; Chang, A. Y.; Goldman, A.

in Geophysical Research Letters (1996), 23(17), 2397--2400

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See detailOn the assessment and uncertainty of atmospheric trace gas burden measurements with high resolution infrared solar occultation spectra from space by the ATMOS Experiment
Abrams, M. C.; Chang, A. Y.; Gunson, M. R.; Abbas, M. M.; Goldman, A.; Irion, F. W.; Michelson, H. A.; Newchurch, M. J.; Rinsland, C. P.; Stiller, G. P.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2337--2340

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See detailStratospheric observations of CH3D and HDO from ATMOS infrared solar spectra: Enrichments of deuterium in methane and implications for HD
Irion, F. W.; Moyer, E. J.; Gunson, M. R.; Rinsland, C. P.; Yung, Y. L.; Michelsen, H. A.; Salawitch, R. J.; Chang, A. Y.; Newchurch, M. J.; Abbas, M. M.; Abrams, M. C.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2381--2384

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See detailThe hydrogen budget of the stratosphere inferred from ATMOS measurements of H2O and CH4
Abbas, M. M.; Gunson, M. R.; Newchurch, M. J.; Michelsen, H. A.; Salawitch, R. J.; Allen, M.; Abrams, M. C.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Moyer, E. J.; Nagaraju, R.; Rinsland, C. P.; Stiller, G. P.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2405--2408

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See detailStratospheric chlorine partitioning: Constraints from shuttle-borne measurements of [HCl], [ClNO3], and [ClO]
Michelsen, H. A.; Salawitch, R. J.; Gunson, M. R.; Aellig, C.; Kämpfer, N.; Abbas, M. M.; Abrams, M. C.; Brown, T. L.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Newchurch, M. J.; Rinsland, C. P.; Stiller, G. P.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2361--2364

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See detailValidation of hydrogen fluoride measurements made by the Halogen Occultation Experiment from the UARS platform
Russell, James M.; Deaver, Lance E.; Luo, Mingzhao; Cicerone, Ralph J.; Park, Jae H.; Gordley, Larry L.; Toon, Geoffrey C.; Gunson, Michael R.; Traub, Wesley A.; Johnson, David G.; Jucks, Kenneth W.; Zander, Rodolphe; Nolt, Ira G.

in Journal of Geophysical Research. Atmospheres (1996), 101(D6), 10163--10174

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See detailATMOS/ATLAS-3 observations of long-lived tracers and descent in the Antarctic Vortex in November 1994
Abrams, M. C.; Manney, G. L.; Gunson, M. R.; Abbas, M. M.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Michelsen, H. A.; Newchurch, M. J.; Rinsland, C. P.; Salawitch, R. J.; Stiller, G. P.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2341--2344

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See detailTrace gas transport in the Arctic Vortex inferred from ATMOS ATLAS-2 observations during April 1993
Abrams, M. C.; Manney, G. L.; Gunson, M. R.; Abbas, M. M.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Michelsen, H. A.; Newchurch, M. J.; Rinsland, C. P.; Salawitch, R. J.; Stiller, G. P.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2345--2348

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See detailSeasonal variations of water vapor in the lower stratosphere inferred from ATMOS/ATLAS-3 measurements of H2O and CH4
Abbas, M. M.; Michelsen, H. A.; Gunson, M. R.; Abrams, M. C.; Newchurch, M. J.; Salawitch, R. J.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Manney, G. L.; Moyer, E. J.; Nagaraju, R.; Rinsland, C. P.; Stiller, G. P.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2401--2404

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See detailStratospheric NO and NO2 abundances from ATMOS Solar-Occultation Measurements
Newchurch, M. J.; Allen, M.; Gunson, M. R.; Salawitch, R. J.; Collins, G. B.; Huston, K. H.; Abbas, M. M.; Abrams, M. C.; Chang, A. Y.; Fahey, D. W.; Gao, R. S.; Irion, F. W.; Loewenstein, M.; Manney, G. L.; Michelsen, H. A.; Podolske, J. R.; Rinsland, C. P.; Zander, Rodolphe

in Geophysical Research Letters (1996), 23(17), 2373--2376

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See detailValidation of hydrogen chloride measurements made by the Halogen Occultation Experiment from the UARS platform
Russell, James M.; Deaver, Lance E.; Luo, Mingzhao; Park, Jae H.; Gordley, Larry L.; Tuck, Adrian F.; Toon, Geoffrey C.; Gunson, Michael R.; Traub, Wesley A.; Johnson, David G.; Jucks, Kenneth W.; Murcray, David G.; Zander, Rodolphe; Nolt, Ira G.; Webster, Christopher R.

in Journal of Geophysical Research. Atmospheres (1996), 101(D6), 10151--10162

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See detailA comparison of measurements from ATMOS and instruments aboard the ER-2 aircraft: Tracers of atmospheric transport
Chang, A. Y.; Salawitch, R. J.; Michelsen, H. A.; Gunson, M. R.; Abrams, M. C.; Zander, Rodolphe; Rinsland, C. P.; Loewenstein, M.; Podolske, J. R.; Proffitt, M. H.; Margitan, J. J.; Fahey, D. W.; Gao, R.-S.; Kelly, K. K.; Elkins, J. W.; Webster, C. R.; May, R. D.; Chan, K. R.; Abbas, M. M.; Goldman, A.; Irion, F. W.; Manney, G. L.; Newchurch, M. J.; Stiller, G. P.

in Geophysical Research Letters (1996), 23(17), 2389--2392

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See detailA comparison of measurements from ATMOS and instruments aboard the ER-2 aircraft: Halogenated gases
Chang, A. Y.; Salawitch, R. J.; Michelsen, H. A.; Gunson, M. R.; Abrams, M. C.; Zander, Rodolphe; Rinsland, C. P.; Elkins, J. W.; Dutton, G. S.; Volk, C. M.; Webster, C. R.; May, R. D.; Fahey, D. W.; Gao, R.-S.; Loewenstein, M.; Podolske, J. R.; Stimpfle, R. M.; Kohn, D. W.; Proffitt, M. H.; Margitan, J. J.; Chan, K. R.; Abbas, M. M.; Goldman, A.; Irion, F. W.; Manney, G. L.; Newchurch, M. J.; Stiller, G. P.

in Geophysical Research Letters (1996), 23(17), 2393--2396

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See detailAPRIL 1993 ARCTIC PROFILES OF STRATOSPHERIC HCL, CLONO2, AND CCL2F2 FROM ATMOSPHERIC TRACE MOLECULE SPECTROSCOPY ATLAS 2 INFRARED SOLAR OCCULTATION SPECTRA
Rinsland, C. P.; Gunson, M. R.; Abrams, M. C.; Lowes, L. L.; Zander, Rodolphe; Mahieu, Emmanuel; Goldman, A.; Irion, F. W.

in Journal of Geophysical Research (1995), 100(D7), 14019-14027

Partitioning among the major components of the stratospheric odd chlorine family inside and outside of the remanent Arctic vortex has been studied on the basis of infrared solar occultation measurements obtained by the atmospheric trace molecule spectroscopy (ATMOS) Fourier transform spectrometer during the ATLAS 2 shuttle mission (April 8-17, 1993). Profiles of hydrogen chloride (HCl) and simultaneous profiles of chlorine nitrate (ClONO2) and CFC-12 (CCl2F2) are reported for examples of in-vortex and out-of-vortex conditions. Increased ClONO2 volume-mixing ratios (VMRs) are measured in the vortex below 20 mbar (similar to 25 km altitude) with a peak ClONO2 VMR of 2.05 +/- 0.45 ppbv (10(-9) per volume) at 56 mbar (similar to 19 km altitude). The reported error correspond to la uncertainties. Simultaneous CCl2F2 and N2O measurements, combined with published empirical relations, indicate that only 0.34 +/- 0.15 ppbv, about 10% of total chlorine, was bound in organic species at the ClONO2 VMR peak in the vortex. A colocated vortex profile of HCl, referenced to simultaneous N2O VMR measurements, has been used to derive a HCl mixing ratio of 1.21 +/- 0.12 ppbv corresponding to the ClONO2 VMR peak. The internal consistency of the ATMOS measurements is demonstrated by the agreement between the total chlorine mixing ratio of 3.60 +/- 0.72 ppbv derived at the ClONO2 VMR peak in the vortex and HCl measurements of 3.37 +/- 0.37 and 3.76 +/- 0.41 ppbv at 0.56 mbar, where HCl is the only significant chlorine-bearing molecule. Outside the vortex the mixing ratio of HCl exceeds the mixing ratio of ClONO2 throughout the stratosphere.

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See detailVERTICAL COLUMN ABUNDANCES OF HCN DEDUCED FROM GROUND-BASED INFRARED SOLAR SPECTRA - LONG-TERM TREND AND VARIABILITY
Mahieu, Emmanuel; RINSLAND, C. P.; Zander, Rodolphe; Demoulin, Philippe; DELBOUILLE, L.; Roland, Ginette

in Journal of Atmospheric Chemistry (1995), 20(3), 299-310

A set of high-resolution IR solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, from 84/06 to 93/06, and at the National Solar Observatory McMath-Pierce solar telescope facility on Kitt Peak, Arizona, U.S.A. from 78/05 to 92/07 have been analyzed to determine the vertical column abundances of hydrogen cyanide, HCN, above the two stations. The analysis was based on least-squares curve fitting of calculated spectra to the observations encompassing the P4 and the P8 lines of HCN respectively located at 3299.5273 and 3287.2483 cm(-1). The results obtained for the two stations indicate that no significant long-term trend affects either of the two databases; however, this analysis reveals variable increases during springtime of up to a factor of 2 in the HCN total column above the Jungfraujoch and even up to 3 above Kitt Peak. The calculated mean vertical column abundances, excluding the spring observations, are equal to (2.55 +/- 0.30) x 10(15) molec./cm(2) (S.D.) and (2.75 +/- 0.30) x 10(15) molec./cm(2) respectively above the Jungfraujoch and the Kitt Peak observatories. Based on a realistic volume mixing ratio profile, these columns translate into mean volume mixing ratios equal to 190 x 10(-12) ppv at the respective altitudes of the stations.

See detailA new analysis of the OH radical spectrum from solar infrared observations.
Mélen, F.; Sauval, A. J.; Grevesse, Nicolas; Farmer, C. B.; Servais, Christian; Delbouille, L.; Roland, G.

in Journal of Molecular Spectroscopy (1995), 174

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See detailImproved spectral parameters for the 16O2 infrared forbidden lines in the X3∑g− (0–1) band
Goldman, A.; Rinsland, C. P.; Canova, B.; Zander, Rodolphe; Dang-Nhu, M.

in Journal of Quantitative Spectroscopy and Radiative Transfer (1995), 54(5), 757-765

New spectral parameters have been generated for the electric quadrupole (eq) and magnetic dipole (md) infrared transitions in the fundamental vibration-rotation 3∑g− (0–1) band of 16O2. Significant improvements in line positions (for both eq and md) and in the long standing problem of the md line intensities, have been achieved by combining recent theoretical work with the analysis of high resolution (0.002 and 0.01 cm−1) solar absorption spectra.

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See detailStratospheric and mesospheric pressure-temperature profiles from rotational analysis of CO2 lines in atmospheric trace molecule spectroscopy/ATLAS 1 infrared solar occultation spectra
Stiller, G. P.; Gunson, M. R.; Lowes, L. L.; Abrams, M. C.; Raper, O. F.; Farmer, C. B.; Zander, Rodolphe; Rinsland, C. P.

in Journal of Geophysical Research. Atmospheres (1995), 100(D2), 3107--3117

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See detailH2SO4 photolysis: A source of sulfur dioxide in the upper stratosphere
Rinsland, C. P.; Gunson, M. R.; Ko, M. K. W.; Weisenstein, D. W.; Zander, Rodolphe; Abrams, M. C.; Goldman, A.; Sze, N. D.; Yue, G. K.

in Geophysical Research Letters (1995), 22(9), 1109--1112

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See detailINCREASE IN LEVELS OF STRATOSPHERIC CHLORINE AND FLUORINE LOADING BETWEEN 1985 AND 1992
Gunson, M. R.; Abrams, M. C.; Lowes, L. L.; Mahieu, Emmanuel; Zander, Rodolphe; Rinsland, C. P.; Ko, M. K. W.; Sze, N. D.; Weisenstein, D. K.

in Geophysical Research Letters (1994), 21(20), 2223-2226

Mixing ratios of 3.44 ppbv (parts per billion by volume) and 1.23 ppbv for HCl and HF above 50 km, surrogates for total chlorine and fluorine, have been measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment on a March 1992 flight of the Space Shuttle. Compared to the measured values obtained on a 1985 flight, these correspond to a 37% and 62% increase for HCl and HF, respectively. The derived trend in HCl (similar to 0.13 ppbv per year) is in good agreement with the model-predicted increase in chlorine loading of 0.13 ppbv per year [Prather and Watson. 1990], and with the measured trends in HCl total column abundance from reported ground-based observations. The main source of this change can be attributed to the release of man-made chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). This new value for HCl represents an upper limit to the inorganic chlorine concentration in the stratosphere available for participation in photochemical processes which destroy ozone.

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See detailProfiles of stratospheric chlorine nitrate (ClONO2) from atmospheric trace molecule spectroscopy/ATLAS 1 infrared solar occultation spectra
Rinsland, Curtis P.; Gunson, M. R.; Abrams, M. C.; Zander, Rodolphe; Mahieu, Emmanuel; Goldman, Aaron; Ko, M. K. W.; Rodriguez, J. M.; Sze, N. D.

in Journal of Geophysical Research (1994), 99(D9), 18895-18900

Stratospheric volume mixing ratio profiles of chlorine nitrate (ClONO2) have been retrieved from 0.01-cm−1 resolution infrared solar occultation spectra recorded at latitudes between 14°N and 54°S by the atmospheric trace molecule spectroscopy Fourier transform spectrometer during the ATLAS 1 shuttle mission (March 24 to April 2, 1992). The results were obtained from nonlinear least squares fittings of the ClONO2 v 4 band Q branch at 780.21 cm−1 with improved spectroscopic parameters generated on the basis of recent laboratory work. The individual profiles, which have an accuracy of about ±20%, are compared with previous observations and model calculations.

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See detailThe identification of 16O 18O 16O and 16O 16O 18O ozone isotopes in high resolution ground-based FTIR spectra
Arlander, Dixon William (Bill); Barbe, Alain; Bourgeois, M.T.; Hamdouni, A.; Flaud, Jean-Marie; Camy-Peyret, Claude; Demoulin, Philippe

in Journal of Quantitative Spectroscopy and Radiative Transfer (1994), 52(3-4), 267271

We present evidence of the 16O 18O 16O and 16O 16O 18O ozone isotopes in the 5 μ region from FTIR solar occultation spectra obtained from the Jungfraujoch Solar Observatory (47°N, 8°E, 3580 m) in Switzerland at a spectral resolution of 0.0025 cm-1 (res.=1/2L). These spectra clearly show numerous unblended lines of the 16O 18O 16O ozone isotope. Laboratory spectra in the 5 μ region of both 50O3 isotopes have been measured and have yielded line positions of the v1+v3 isotopic bands which can eventually lead to their retrieval from measured ground-based solar occulation spectra. Although retrieval of 16O 16O 18O could be difficult due to slight line blending, identification of several lines is shown.

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See detailSECULAR TREND AND SEASONAL VARIABILITY OF THE COLUMN ABUNDANCE OF N2O ABOVE THE JUNGFRAUJOCH STATION DETERMINED FROM IR SOLAR SPECTRA
Zander, Rodolphe; EHHALT, D. H.; RINSLAND, Curtis P.; SCHMIDT, U.; Mahieu, Emmanuel; RUDOLPH, J.; Demoulin, Philippe; Roland, Ginette; Delbouille, Luc; Sauval, A. J.

in Journal of Geophysical Research (1994), 99(D8), 16745-16756

Infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch (3580 m altitude), Switzerland, in 1950-1951 and from 1984 to 1992 have been analyzed to determine vertical column abundances of nitrous oxide (N2O) above the station. The best fit to the relatively dense set of measurements made between 1984 and 1992 indicates a mean exponential rate of increase equal to 0.36 +/- 0.06% yr-1 (1 sigma) and a seasonal modulation of 7.2% peak to peak, the minimum occurring at the end of the winter and the maximum in early September. The column abundances for April of the years 1951, 1984, and 1992 were found equal to 3.49 x 10(18), 3.76 x 10(18), and 3.87 x 10(18) molecules cm-2, respectively; they translate into N2O concentrations at the altitude of the Jungfraujoch equal to 275, 296, and 305 parts per billion by volume. These results indicate that the exponential rate of increase for 1951-1984 was equal to 0.23 +/- 0.04% yr-1 (1 sigma), thus substantially lower than for the 1984-1992 time interval and that the so-called preindustrial levels of N2O pertained until 1951 with most of the increase in atmospheric N2O occurring thereafter.

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See detailIncrease of carbonyl fluoride (COF2) in the stratosphere and its contribution to the 1992 budget of inorganic fluorine in the upper stratosphere
Zander, Rodolphe; Rinsland, Curtis P.; Mahieu, Emmanuel; Gunson, M. R.; Farmer, C. B.; Abrams, M. C.; Ko, M. K. W.

in Journal of Geophysical Research (1994), 99(D8), 16737-16743

Volume mixing ratio profiles of COF2 have been derived through most of the stratosphere between 30°N and 54°S from series of 0.01-cm−1 resolution infrared solar spectra recorded in the occultation mode by the atmospheric trace molecule spectroscopy (ATMOS) instrument during the ATLAS 1 space shuttle mission of March–April 1992. When compared with similar results obtained from the ATMOS/Spacelab 3 mission of April–May 1985, the cumulative increase in the burden of COF2 in the middle and upper stratosphere was found to be 67% for that 7-year time interval. By combining a subset of these COF2 results with upper stratospheric concentrations of HF also derived from the ATMOS observations, it was further found that the budget of inorganic fluorine above 35 km altitude increased by (60 ± 10) % over the 1985–1992 time interval, which corresponds to an average exponential rate of increase of (6.7 ± 1.1) % yr−1, or a linear rate of increase referenced to 1985 of (8.5 ± 1.3) % yr−1 at the 1σ confidence level. The total inorganic F atom volume mixing ratio found in the upper stratosphere for 1985 and 1992 and the increase during this period mirror the rise in man-made fluorine-bearing compounds at the ground during the early to mid 1980s. This demonstrates the negligible impact of natural sources of fluorine, in particular volcanic activity, on the observed change of F in the upper stratosphere. Implications of the present findings and comparison with model results are discussed.

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See detailMonitoring of the atmospheric burdens of CH4, N2O, CO, CHCIF2 and CF2Cl2 above Central Europe during the last decade
Zander, Rodolphe; Demoulin, Philippe; Mahieu, Emmanuel

in Environmental Monitoring and Assessment (1994, May), 31(1-2), 203-209

Based on high spectral resolution infrared solar observations made at the International Scientific Station of the Jungfraujoch, Switzerland, total vertical column abundances of 18 atmospheric gases have been monitored routinely since 1984. The observed temporal evolutions in the columns of CH4, N2O, CO, CHClF2 (HCFC-22) and CF2Cl2 (CFC-12) are reported here as typical examples of this monitoring effort which is conducted within the frame of ''Global Change'' and ''Network for the Detection of Stratospheric Change'' programs.

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See detailSECULAR EVOLUTION OF THE VERTICAL COLUMN ABUNDANCES OF CHCLF2 (HCFC-22) IN THE EARTH'S ATMOSPHERE INFERRED FROM GROUND-BASED IR SOLAR OBSERVATIONS AT THE JUNGFRAUJOCH AND AT KITT-PEAK, AND COMPARISON WITH MODEL-CALCULATIONS
Zander, Rodolphe; Mahieu, Emmanuel; Demoulin, Philippe; Rinsland, Curtis P.; Weisenstein, Debra K.; Ko, Malcolm K. W.; Sze, Nien Dak; Gunson, Michael R.

in Journal of Atmospheric Chemistry (1994), 18(2), 129-148

Series of high-resolution infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, between 06/1986 and 11/1992, and at Kitt Peak National Observatory, Tucson, Arizona (U.S.A.), from 12/1980 to 04/1992, have been analyzed to provide a comprehensive ensemble of vertical column abundances of CHClF2 (HCFC-22; Freon-22) above the European and the North American continents. The columns were derived from nonlinear least-squares curve fittings between synthetic spectra and the observations containing the unresolved 2nu6 Q-branch absorption of CHClF2 at 829.05 cm-1. The changes versus time observed in these columns were modeled assuming both an exponential and a linear increase with time. The exponential rates of increase at one-sigma uncertainties were found equal to (7.0 +/- 0.35)%/yr for the Junfraujoch data and (7.0 +/- 0.23)%/yr for the Kitt Peak data. The exponential trend of 7.0%/yr found at both stations widely separated in location can be considered as representative of the global increase of the CHClF2 burden in the Earth's atmosphere during the period 1980 to 1992. When assuming two realistic vertical volume mixing ratio profiles for CHClF2 in the troposphere, one quasi constant and the other decreasing by about 13% from the ground to the tropopause, the concentrations for mid-1990 were found to lie between 97 and 111 pptv (parts per trillion by volume) at the 3.58 km altitude of the Jungfraujoch and between .97 and 103 pptv at Kitt Peak, 2.09 km above sea level. Corresponding values derived from calculations using a high vertical resolution-2D model and recently compiled HCFC-22 releases to the atmosphere, were equal to 107 and 105 pptv, respectively, in excellent agreement with the measurements. The model calculated lifetime of CHClF2 was found equal to 15.6 years. The present results are compared critically with similar data found in the literature. On average, the concentrations found here are lower by 15-20% than those derived from in situ investigations; this difference cannot be explained by the absolute uncertainty of +/- 11% assigned presently to the infrared remote measurements.

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See detailHeterogeneous conversion of N2O5 to HNO3 in the post-Mount Pinatubo eruption stratosphere
Rinsland, Curtis P.; Gunson, Michaël R.; Abrams, M. C.; Lowes, L. L.; Zander, Rodolphe; Mahieu, Emmanuel; Goldman, Aaron; Ko, M. K. W.; Rodriguez, J. M.; Sze, Nien Dak

in Journal of Geophysical Research (1994), 99(D4), 8213-8219

Simultaneous stratospheric volume mixing ratio (VMR) profiles of dinitrogen pentoxide (N2O5) and nitric acid (HNO3) at sunrise between 25-degrees-N and 15-degrees-S latitude and profiles of HNO3 at sunset between 42-degrees-S and 53-degrees-S latitude have been derived from 0.01 cm-1 resolution infrared solar occultation spectra recorded 9 1/2 months after the massive eruption of the Mount Pinatubo volcano in the Philippine Islands. The measurements were obtained by the atmospheric trace molecule spectroscopy (ATMOS) Fourier transform spectrometer during the ATLAS 1 shuttle mission (March 24 to April 2, 1992). The measured HNO3 VMRs are higher at all altitudes and latitudes than corresponding values measured by the limb infrared monitor of the stratosphere (LIMS) instrument during the same season in 1979, when the aerosol loading was near background levels. The largest relative increase in the HNO3 VMR occurred near the equator at 30-km altitude, where the ATMOS/ATLAS 1 values are about a factor of 2 higher than the LIMS measurements. Two-dimensional model calculations show that the increase in HNO3 and the ATMOS/ATLAS 1 measurement of a steep decrease in the N2O5 VMR below 30 km can be explained by the enhanced conversion of N2O5 to HNO3 on the surfaces of the Mount Pinatubo sulfate aerosols. Our profile results demonstrate the global impact of the N2O5 + H2O --> 2HNO3 heterogeneous reaction in altering the partitioning of stratospheric odd nitrogen after a major volcanic eruption.

See detailMid-infrared extinction by sulfate aerosols from the Mt Pinatubo eruption
Rinsland, C. P.; Yue, G. K.; Gunson, M. R.; Zander, Rodolphe; Abrams, M. C.

in Journal of Quantitative Spectroscopy and Radiative Transfer (1994), 52(3), 241-252

Quantitative measurements of the wavelength dependence of aerosol extinction in the 750–3400 cm-1 spectral region have been derived from 0.01 cm-1 resolution stratospheric solar occultation spectra recorded by the ATMOS (Atmospheric Trace Molecule Spectroscopy) Fourier transform spectrometer about 912 months after the Mt Pinatubo volcanic eruption. Strong, broad aerosol features have been identified near 900, 1060, 1720, and 2900 cm-1 below a tangent height of ~30 km. Aerosol extinction measurements derived from ~0.05 cm-1 wide microwindows nearly free of telluric line absorption in the ATMOS spectra are compared with transmission calculations derived from aerosol size distribution profiles retrieved from correlative SAGE (Stratospheric Aerosol and Gas Experiment) II visible and near i.r. extinction measurements, seasonal and zonally averaged H2SO4 aerosol weight percentage profiles, and published sulfuric acid optical constants derived from room temperature laboratory measurements. The calculated shapes and positions of the aerosol features are generally consistent with the observations, thereby confirming that the aerosols are predominantly concentrated H2SO4-H2O droplets, but there are significant differences between the measured and calculated wavelength dependences of the aerosol extinction. We attribute these differences as primarily the result of errors in the calculated low temperature H2SO4-H2O optical constants. Errors in both the published room temperature optical constants and the limitations of the Lorentz-Lorenz relation are likely to be important.

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See detailATMOS ATLAS-1 MEASUREMENTS OF SULFUR-HEXAFLUORIDE (SF6) IN THE LOWER STRATOSPHERE AND UPPER TROPOSPHERE
Rinsland, C. P.; Gunson, M. R.; Abrams, M. C.; Lowes, L. L.; Zander, Rodolphe; Mahieu, Emmanuel

in Journal of Geophysical Research (1993), 98(D11), 20491-20494

Vertical profiles of sulfur hexafluoride (SF6) in the lower stratosphere and upper troposphere have been retrieved from 0.01-cm-1 resolution infrared solar occultation spectra recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the ATLAS (Atmospheric Laboratory for Applications and Science) 1 shuttle mission of March 24 to April 2, 1992. Based on measurements of the unresolved absorption by the SF6 nu3 band Q branch at 947.9 cm-1, average SF6 volume mixing ratios and 1-sigma uncertainties of 3.20 +/- 0.54 parts per trillion by volume (pptv; 10(-12) ppv) at 200 mbar (approximately 11.8 km) declining to 2.86 +/- 0.29 pptv at 100 mbar (approximately 16.2 km) and 1.95 +/- 0.50 pptv at 30 mbar (approximately 23.9 km) have been retrieved. The profiles show no obvious dependence with latitude over the range of the measurements (eight occultations spanning 28-degrees-S to 54-degrees-S). Assuming an exponential growth model and applying a correction for the interhemispheric concentration difference, an average SF6 rate of increase of 8.7 +/- 2.2% per year, 2 sigma, between 12 and 18 km has been derived by fitting the present measurements, ATMOS measurements from the April-May 1985 Spacelab 3 mission, and balloon-borne IR measurements obtained in March 1981 and June 1988.

See detailLes missions spatiales ATMOS: des flashes sur notre atmosphère en évolution
Sauval, J.; Zander, Rodolphe

in Ciel et Terre (1993), 109

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See detailGROUND-BASED INFRARED MEASUREMENTS OF CARBONYL SULFIDE TOTAL COLUMN ABUNDANCES - LONG-TERM TRENDS AND VARIABILITY
RINSLAND, C. P.; Zander, Rodolphe; Mahieu, Emmanuel; Demoulin, Philippe; GOLDMAN, A.; EHHALT, D. H.; RUDOLPH, J.

in Journal of Geophysical Research (1992), 97(D5), 5995-6002

Total vertical column abundances of carbonyl sulfide (OCS) have been derived from time series of high-resolution infrared solar absorption spectra recorded at the National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.09 km, latitude 31.9-degrees-N, longitude 111.6-degrees-W), southwest of Tucson, Arizona, and at the International Scientific Station of the Jungfraujoch (altitude 3.58 km, latitude 46.5-degrees-N, longitude 8.0-degrees-E), in the Swiss Alps. The analysis of both data sets is based on nonlinear least squares spectral fittings of narrow intervals centered on lines of the intense nu-3 band of OCS, the P(37) transition at 2045.5788 cm-1 and the P(15) transition at 2055.8609 cm-1, with a consistent set of spectroscopic line parameters. The Kitt Peak measurements, recorded on 30 different days between May 1977 and March 1991, show a 10% peak-to-peak seasonal cycle with a summer maximum and a winter minimum and a trend in the total column abundance equal to (0.1 +/- 0.2)% yr-1, 2-sigma. Jungfraujoch solar spectra recorded on 67 different days between October 1984 and April 1991 have been analyzed. The fitted trend in the Jungfraujoch total columns, (-0.1 +/- 0.5)% yr-1, 2-sigma, is consistent with the Kitt Peak trend results within the errors. The Jungfraujoch total columns show a more complex seasonal variation than noted in the Kitt Peak data. The mean of the daily averaged total columns, 8.44 x 10(15) molecules cm-2 above Kitt Peak and 6.41 x 10(15) molecules cm-2 above the Jungfraujoch station, correspond respectively to mean tropospheric mixing ratios of 0.54 +/- 0.04 and 0.52 +/- 0.04 parts per billion by volume; these values are consistent with previously reported remote and in situ measurements. Taken together, the results from the two sites indicate that there has been no significant change in the OCS total column abundance at northern mid-latitudes over the last decade.

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See detailThe 1985 chlorine and fluorine inventories in the stratosphere based on atmos observations at 30-degrees north latitude
Zander, Rodolphe; Gunson, Michael R.; Farmer, Crofton B.; Rinsland, Curtis P.; Irion, F. W.; Mahieu, Emmanuel

in Journal of Atmospheric Chemistry (1992), 15(2), 171-186

The set of high-resolution infrared solar observations made with the Atmospheric Trace Molecule Spectroscopy (ATMOS) - Fourier transform spectrometer from onboard Spacelab 3 (30 April-1 May 1985) has been used to evaluate the total budgets of the odd chlorine and fluorine chemical families in the stratosphere. These budgets are based on volume mixing ratio profiles measured for HCl, HF, CH3Cl, ClONO2, CCl4, CCl2F2, CCl3F, CHClF2, CF4, COF2, and SF6, near 30-degrees north latitude. When including realistic concentrations for species not measured by ATMOS, i.e., the source gases CH3CCl3, and C2F3Cl3 below 25 km, and the reservoirs ClO, HOCl and COFCl between 15 and 40 km (five gases actually measured by other techniques), the 30-degrees-N zonal 1985 mean total mixing ratio of chlorine, Cl, was found to be equal to (2.58 +/- 0.10) ppbv (parts per billion by volume) throughout the stratosphere, with no significant decrease near the stratopause. The results for total fluorine indicate a slight, but steady, decrease of its volume mixing ratio with increasing altitude, around a mean stratospheric value of (1.15 +/- 0.12) ppbv. Both uncertainties correspond to one standard deviation. These mean springtime 1985 stratospheric budgets are commensurate with values reported for the tropospheric Cl and F concentrations in the early 1980s, when allowance is made for the growth rates of their source gases at the ground and the time required for tropospheric air to be transported into the stratosphere. The results are discussed with emphasis on conservation of fluorine and chlorine and the partitioning among source, sink, and reservoir gases throughout the stratosphere.

See detailRemote sensing of the atmosphere by high resolution infrared absorption spectroscopy
Brown, L.R.; Farmer, C.B.; Rinsland, C.P.; Zander, Rodolphe

in Rao, K.N.; Weber, A. (Eds.) Spectroscopy of the earth's Atmosphere and interstellar Medium (1992)

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See detailMiddle and upper atmosphere pressure-temperature profiles and the abundances of CO2 and CO in the upper atmosphere from ATMOS/Spacelab 3 observations
Rinsland, C. P.; Gunson, M. R.; Zander, Rodolphe; López-Puertas, M.

in Journal of Geophysical Research. Atmospheres (1992), 97(D18), 20479--20495

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See detailInfrared Spectroscopic Measurements of the Vertical Column Abundance of Sulfur Hexafluoride, SF6, From the Ground
Zander, Rodolphe; Rinsland, C.P.; Demoulin, Philippe

in Journal of Geophysical Research (1991), 96(D8), 15447-15454

The unresolved v3 band Q branch of sulfur hexafluoride, SF6, at 947.9 cm-1 has been identified and quantitatively analyzed in series of high-quality infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, and at the National Solar Observatory facility on Kitt Peak in Arizona. Series of monthly mean total vertical column abundances of SF6 above both stations, deduced from that feature with line-by-line nonlinear least squares fitting methods, are reported over the time intervals from June 1986 to June 1990 for the Jungfraujoch and from March 1981 to June 1990 for Kitt Peak. Assuming an exponential growth model for fitting these series of measurements, it is found that the vertical column abundances have increased at mean rates of 6.9 +- 2.8 %/yr above the Jungfraujoch (calculated columns of 2.99 x 10E13 molecules/cm2 in June 1986 and 3 94 x 10E13 molecules/cm2 in June 1990) and 6.6 +- 7.2 %/yr above Kitt Peak (calculated columns equal to 2.97 x 10E13 molecules/cm2 in June 1981 and 5.38 x 10E13 molecules/cm2 in June 1990), the uncertainties corresponding to 2 sigma confidence levels. These results are further discussed within the context of variability and compared with previously published measurements.

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See detailDetermination of Absolute Strengths of N2 Quadrupole Lines From High-Resolution Ground-based IR Solar Observations
Demoulin, Philippe; Farmer, C.B.; Rinsland, C.P.; Zander, Rodolphe

in Journal of Geophysical Research (1991), 96(D7), 13003-13008

High-resolution, high signal-to-noise ratio, solar absorption spectra recorded with a Fourier transform spectrometer at the International Scientific Station of the Jungfraujoch, Switzerland, have been analyzed to determine the strengths of several lines belonging to the S branch of the N2 (1-0) electric quadrupole vibration-rotation band centered at 2329.9168 cm-1. The method which was applied here was based on equivalent width measurements of lines observed over a broad range of air masses; extrapolation of these measurements to zero air mass gave the line strengths for the transitions S7 to S10, independent of half widths, an ambiguity unavoidable with the use of curve-fitting techniques. The resulting absolute accuracies of the line strengths derived here, estimated to be better than +-2.5% for S8, +-2.6% for S10, +-3.4% for S9, and +-5.1% for S7, are due largely to the high quality and quantity of the spectra retained in this analysis and the accuracy with which the observation conditions are known. An important application of the improved values for these N2 transitions, which have low initial ground state energies, is the direct determination of the line-of-sight atmospheric air masses associated with remotely sensed infrared spectroscopic observations. Positions of the N2 transitions studied here have further been redetermined with an absolute accuracy better than 0.0002 cm-1.

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See detailGround-Based Infrared Measurements of HNO3 Total Column Abundances: Long-Term Trend and Variability
Rinsland, C.P.; Zander, Rodolphe; Demoulin, Philippe

in Journal of Geophysical Research (1991), 96(D5), 9379-9389

The long-term trend and variability of the total column amount of atmospheric nitric acid (HNO3) have been investigated based on time series of infrared solar absorption spectra recorded at two remote high-altitude sites, the International Scientific Station of the Jungfraujoch (ISSJ) in the Swiss Alps (altitude 3.6 km, latitude 46.5°N, longitude 8.0°E) and the National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.1 km, latitude 31.9°N, longitude 111.6°W), southwest of Tucson, Arizona. The HNO3 v5 band Q branch at 879.1 cm-1 and three P branch manifolds near 869 cm-1 were analyzed using a nonlinear least squares spectral fitting technique and a consistent set of spectroscopic line parameters. The ISSJ measurements evaluated in the present work consist of two solar spectra recorded with a grating spectrometer in June 1951 and a set of observations obtained with a high-resolution Fourier transform spectrometer between June 1986 and June 1990. The modern ISSJ measurements show a ~20% peak-to-peak amplitude seasonal cycle with a winter maximum superimposed on significant variability and a summer minimum; the June results from 1986 to 1990 are both higher and lower than the two retrieved June 1951 HNO3 total column amounts. The fitted trend, (-0.16 +- 0.50) %/yr, 2 sigma, indicates that there has been no detectable change in the HNO3 total column over the last 4 decades. The Kitt Peak measurements, recorded with a high-resolution Fourier transform spectrometer between December 1980 and June 1990, also show marked variability in the HNO3 total column, but in contrast to the ISSJ measurements, no obvious seasonal cycle is observed. The deduced trend in the total column above Kitt Peak, (-0.8 +- 1.6) %/yr, 2 sigma, is consistent with the ISSJ time series of measurements, in that no significant HNO3 long-term trend has been found. The sets of measurements from the two sites are compared with each other and with previously published results, with emphasis on the reported variability of HNO3 and the changes in the HNO3 total column with season and latitude.

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See detailSeasonal Cycle and Secular Trend of the Total and Tropospheric Column Abundance of Ethane Above the Jungfraujoch
Ehhalt, D.H.; Schmidt, U.; Zander, Rodolphe; Demoulin, Philippe; Rinsland, C.P.

in Journal of Geophysical Research (1991), 96(D3), 4985-4994

Total column abundances of ethane (C2H6) above the Jungfraujoch Station, Switzerland, 3.58-km altitude, have been deduced from infrared solar spectra recorded in 1951 and from 1984 to 1988. The results were derived from the spectroscopic analysis of the v7 band PQ3, PQ1, and RQ0 subbranches of C2H6 near 2976.8, 2983.4, and 2986.7 cm-1, respectively. The 1984-1988 results obtained from more than 300 observations at 0.005 cm-1 resolution show a definite seasonal variation in the total vertical column abundance of that gas, with a maximum of (1.43 +- 0.03) x 10E16 molecules/cm2 during March and April and a minimum in the fall. The corresponding C2H6 mixing ratio in the free troposphere was derived to 1.53 +- 0.14 ppb in early April; the ratio of maximum to minimum C2H6 concentration in the troposphere was found to be 1.88 +- 0.12. From the analysis of the same spectral features observed in March and April 1951, we have deduced a total vertical column abundance of (1.09 +- 0.10) x 10E16 molecules/cm2. Assuming an exponential increase with time and correcting for a small decrease in the stratospheric amount of C2H6 due to the man-induced increase in stratospheric chlorine, we obtain a secular trend in the tropospheric burden above the Jungfraujoch equal to (0.85 +- 0.3)%/yr. It is argued that this trend is valid for the entire northern hemisphere.

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See detailVertical Column Abundances and Seasonal Cycle of Acetylene, C2H2, above the Jungfraujoch Station, Derived from IR Solar observations
Zander, Rodolphe; Rinsland, C.P.; Ehhalt, D.H.; Rudolph, J.; Demoulin, Philippe

in Journal of Atmospheric Chemistry (1991), 13

Monthly mean total vertical column abundances of acetylene have been determined from series of infrared solar spectra recorded at the Jungfraujoch station, Switzerland, between June 1986 and April 1991. The data have been obtained by nonlinear least-squares fittings of the v5 band R19 transition of C2H2 at 776.0818 cm-1. The average of 22 monthly mean total vertical columns of C2H2 retrieved during that time interval of almost 5 years was found to be equal to (1.81 +- O.12) X 1OE15 molec/cm2, which corresponds to an average mixing ratio of (0.22 +- O.013) ppbv (parts per billion by volume) in a troposphere extending from the altitude of the station (3.58 km), up to 10.5 km. Despite the large variability found from year to year, a least-squares sine fit to the data reveals a seasonal variation with an amplitude of about +- 40 % of the mean; the maximum occurs during mid-winter and the minimum in the summer. The present results are compared critically with similar in-situ data found in the literature. A sinusoidal fit to ail such free troposphere measurements made in-situ between 30° N and 60° N indicates good agreement in shape and phase with the seasonal variation derived above the Jungfraujoch, but their average column abundance, 2.3 X lOE15 molec/cm2, is about 30 % higher; this difference is explained on the basis of non-upwelling meteorological conditions generally prevailing during ground-based remote solar observations.

See detailThe fundamental quadrupole band of 14N2: Line positions from high-resolution stratospheric solar absorption spectra
Rinsland, C. P.; Zander, Rodolphe; Goldman, A.; Murcray, F. J.; Murcray, D. G.; Gunson, M. R.; Farmer, C. B.

in Journal of Molecular Spectroscopy (1991), 148(1), 274-279

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See detailTwo-dimensional model calculation of fluorine-containing reservoir species in the stratosphere
Kaye, Jack A.; Douglass, Anne R.; Jackman, Charles H.; Stolarski, Richard S.; Zander, Rodolphe; Roland, G.

in Journal of Geophysical Research. Atmospheres (1991), 96(D7), 12865--12881

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See detailStratospheric profiles of heavy water vapor isotopes and CH3D from analysis of the ATMOS Spacelab 3 infrared solar spectra
Rinsland, C. P.; Gunson, M. R.; Foster, J. C.; Toth, R. A.; Farmer, C. B.; Zander, Rodolphe

in Journal of Geophysical Research. Atmospheres (1991), 96(D1), 1057--1068

See detailIdentification of magnetic dipole infrared transitions of the fundamental band of oxygen
Dang-Nhu, M; Zander, Rodolphe; Goldman, A; Rinsland, CP

in Journal of Molecular Spectroscopy (1990), 144(2), 366-373

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See detailStratospheric methane concentration profiles measured during the Balloon Intercomparison Campaigns
Zander, Rodolphe; Louisnard, N.; Bangham, M.

in Journal of Atmospheric Chemistry (1990), 10(2), 145-158

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See detailStratospheric ClONO2, HCl, and HF concentration profiles derived from Atmospheric Trace Molecule Spectroscopy Experiment Spacelab 3 observations: An update
Zander, Rodolphe; Gunson, M. R.; Foster, J. C.; Rinsland, C. P.; Namkung, J.

in Journal of Geophysical Research. Atmospheres (1990), 95(D12), 20519--20525

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See detailMeasurements of CH4, N2O, CO, H2O, and O3 in the middle atmosphere by the Atmospheric Trace Molecule Spectroscopy experiment on Spacelab 3
Gunson, M. R.; Farmer, C. B.; Norton, R. H.; Zander, Rodolphe; Rinsland, C. P.; Shaw, J. H.; Gao, B.-C.

in Journal of Geophysical Research. Atmospheres (1990), 95(D9), 13867--13882

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See detailIntercomparison of stratospheric water vapor profiles obtained during the Balloon Intercomparison Campaign
Murcray, D.; Goldman, A.; Kosters, J.; Zander, Rodolphe; Evans, W.; Louisnard, N.; Alamichel, C.; Bangham, M.; Pollitt, S.; Carli, B.; Dinelli, B.; Piccioli, S.; Volboni, A.; Traub, W.; Chance, K.

in Journal of Atmospheric Chemistry (1990), 10(2), 159-179

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See detailIntercomparison of measurements of stratospheric hydrogen fluoride
Mankin, Williamg; Coffey, M. T.; Chance, K. V.; Traub, W. A.; Carli, B.; Mencaraglia, F.; Piccioli, S.; Nolt, I. G.; Radostitz, J. V.; Zander, Rodolphe; Roland, G.; Johnson, Douglasw; Stokes, Geraldm; Farmer, C. B.; Seals, R. K.

in Journal of Atmospheric Chemistry (1990), 10(2), 219-236

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See detailBalloon Intercomparison Campaigns: Results of remote sensing measurements of HCl
Farmer, C. B.; Carli, B.; Bonetti, A.; Carlotti, M.; Dinelli, B. M.; Fast, H.; Evans, W. F. J.; Louisnard, N.; Alamichel, C.; Mankin, W.; Coffey, M.; Nolt, I. G.; Murcray, D. G.; Goldman, A.; Stokes, G. M.; Johnson, D. W.; Traub, W. A.; Chance, K. V.; Zander, Rodolphe; Roland, G.; Delbouille, L.

in Journal of Atmospheric Chemistry (1990), 10(2), 237-272

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See detailSecular Increase of the Vertical Column Abundance of Methane Derived From IR Solar Spectra Recorded at the Jungfraujoch Station
Zander, Rodolphe; Demoulin, Philippe; Ehhalt, D.H.; Schmidt, U.

in Journal of Geophysical Research (1989), 94(D8), 11029-11039

Using all of the pertinent infrared solar spectra recorded at the Jungfraujoch Station, Switzerland, in 1951, 1975, and in 1984-1987, the increase of the vertical column abundance of methane, CH4, above that station has been reevaluated. The results are based on equivalent widths measurements of both the R0 and the R5 transitions of the 2v3 band of CH4 at 6015.66 and 6067.09 cm-1 and on the CH4-v3 band absorption characteristics between 2905.0 and 2908.8 cm-1. The data between 1984 and 1987 provide a full seasonal cycle. They demonstrate a significant annual variation in the column abundance of CH4 of +- 10% around the mean. They also show variability on shorter time scales. The mean cumulative rate of increase of the total vertical column abundance of CH4 above the Jungfraujoch is found to be (0.7 +- 0.1) %/yr between 1951 and 1986. Using a realistic CH4 concentration profile throughout the troposphere and the stratosphere, we deduce volume mixing ratios at the altitude of the Jungfraujoch, equal to 1.28 +- 0.08 and 1.64 +- 0.09 ppm, for 1951 and for 1985-1987, respectively.

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See detailSecular Increase of the Total Vertical Column Abundance of Carbon Monoxide Above Central Europe Since 1950
Zander, Rodolphe; Demoulin, Philippe; Ehhalt, D.H.; Schmidt, U.; Rinsland, C.P.

in Journal of Geophysical Research (1989), 94(D8), 11021-11028

The secular increase of the total vertical column abundance of carbon monoxide has been derived from sets of infrared solar spectra recorded from an altitude of 3.58 km at the Jungfraujoch Station, Switzerland, in 1950-1951 and in 1985-1987. The results are based on equivalent width measurements of the R3 line of the 1-0 vibration-rotation band of 12C160 at 2159.30 cm-1. The set of 1985-1987 observations indicates a strong seasonal cycle in the total column abundance of CO, with a +- 25 % modulation between minimum values in late summer and the maximum values in late winter. Variability on shorter time scales is also present in both the old and recent data sets. The mean cumulative rate of increase of the total column abundance of CO above the Jungfraujoch is found to be (0.85 +- 0.20) %/yr between 1950-1951 and 1985-1987. The present findings are compared with trends reported in earlier studies.

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See detailStratospheric infrared continuum absorptions observed by the ATMOS instrument
Rinsland, C. P.; Zander, Rodolphe; Namkung, J. S.; Farmer, C. B.; Norton, R. H.

in Journal of Geophysical Research. Atmospheres (1989), 94(D13), 16303--16322

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See detailSpectroscopic Evidence for the Presence of the v4-Q Branch of Chlorine Nitrate (ClONO2) in Ground-Based Infrared Solar Spectra
Zander, Rodolphe; Demoulin, Philippe

in Journal of Atmospheric Chemistry (1988), 6

The investigation of infrared solar spectra recorded at the lnternational Scientific Station of the Jungfraujoch, Switzerland, with a high spectral resolution Fourier transform spectrometer, has revealed an absorption feature between 780.15 and 780.28 cm-1 which we have identified as the v4-Q branch of ClONO2 near 780.21 cm-1. While no details of the distribution versus altitude have been deduced from the data available so far, the analysis of June 1986 observations leads to a mean day-time column density of chlorine nitrate above the Jungfraujoch, equal to (1.15 +- 0.3) E15 mol./cm2. This value is in good agreement with recently published ClONO2 results obtained during the ATMOS/SL3 mission at 30°N latitude. The present research represents an important step towards assessing the possibility of monitoring the telluric ClONO2 column density from high mountain based stations.

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See detailIntercomparison of NO Column Measurements During MAP/GLOBUS 1985
McKenzie, R.L.; Matthews, W.A.; Kondo, Y.; Zander, Rodolphe; Demoulin, Philippe; Fabian, P.; Murcray, D.G.; Murcray, F.J.; Lado-Bordowsky, O.; Camy-Peyret, Claude; Roscoe, H.K.; Pyle, J.A.; Mc Peters, R.D.

in Journal of Atmospheric Chemistry (1988), 7

Column measurements of nitric oxide were made using several techniques during the MAP/GLOBUS campaign in France in September 1985. The data sets are nearly co-located and simultaneous, therefore allowing a valid intercomparison of the various measurement methods. The range of altitudes sampled differs from instrument to instrument. This complicates the comparison because the data sets are to some extent complementary. The NO distributions apparently vary significantly from day to day, and possibly over shorter timescales. Changes in dynamics may be responsible for these variations. The results from the instruments which measure in the infrared and the ultraviolet are self-consistent, and show good agreement with photochemical predictions. On 19 September, when the intercomparison was made, the profile measured by the in-situ chemi- luminescent instrument differed significantly from the predicted profile, and the measured columns were generally higher.

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See detailConcentrations of carbonyl sulfide and hydrogen cyanide in the free upper troposphere and lower stratosphere deduced from ATMOS/Spacelab 3 infrared solar occultation spectra
Zander, Rodolphe; Rinsland, C. P.; Farmer, C. B.; Namkung, J.; Norton, R. H.; Russell, J. M.

in Journal of Geophysical Research. Atmospheres (1988), 93(D2), 1669--1678

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See detailMeasurements of odd nitrogen compounds in the stratosphere by the ATMOS experiment on Spacelab 3
Russell, J. M.; Farmer, C. B.; Rinsland, C. P.; Zander, Rodolphe; Froidevaux, L.; Toon, G. C.; Gao, B.; Shaw, J.; Gunson, M.

in Journal of Geophysical Research. Atmospheres (1988), 93(D2), 1718--1736

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See detailInfrared spectroscopic measurements of halogenated sink and reservoir gases in the stratosphere with the ATMOS instrument
Raper, O. F.; Farmer, C. B.; Zander, Rodolphe; Park, J. H.

in Journal of Geophysical Research. Atmospheres (1987), 92(D8), 9851--9858

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See detailInfrared spectroscopic measurements of halogenated source gases in the stratosphere with the ATMOS instrument
Zander, Rodolphe; Rinsland, C. P.; Farmer, C. B.; Norton, R. H.

in Journal of Geophysical Research. Atmospheres (1987), 92(D8), 9836--9850

See detailConcentrations of hydrogen chloride and hydrogen fluoride measured during the MAP/GLOBUS campaign of September 1983
Zander, Rodolphe; Roland, G.; Delbouille, L.; Sauval, A. J.; Marché, P.; Karcher, F.; Amoudei, M.; Dufour, B.

in Planetary and Space Science (1987), 35(5), 665-672

Within the context of the MAP/GLOBUS campaign of September 1983, several trace species have been observed by absorption spectroscopy at the two ground stations of the Jungfraujoch, Switzerland (3580 m altitude) and the Observatoire de Haute-Provence, France (1905 m altitude). The results obtained for HCl and for HF, expressed in terms of mean integrated columns above these sites are: Jungfraujoch: (2.1 ± 0.2) E15 mol cm−2 HCl (4.8 ± 0.2) E14 mol cm−2 HF Haute-Provence: (2.6 ± 0.2) E15 mol cm−2 HCl. Taking into account the difference in the altitude of the two stations, the reported HCl results are in agreement to within their respective uncertainties. The integrated column density of HCl and HF above 11 km altitude, deduced from airplane observations on 9 September 1983, are: (1.65 ± 0.25) E15 mol cm−2 HCl above 11 km (3.7 ± 1.7) E14 mol cm−2 HF above 10 km supporting satisfactorily the ground measurements.

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See detailMonitoring of the integrated column of hydrogen fluoride above the Jungfraujoch Station since 1977 — the HF/HCl column ratio
Zander, Rodolphe; Roland, G.; Delbouille, L.; Sauval, A.; Farmer, C. B.; Norton, R. H.

in Journal of Atmospheric Chemistry (1987), 5(4), 385-394

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See detailConcentrations of ethane (C2H6) in the lower stratosphere and upper troposphere and acetylene (C2H2) in the upper troposphere deduced from atmospheric trace molecule spectroscopy/Spacelab 3 spectra
Rinsland, C. P.; Zander, Rodolphe; Farmer, C. B.; Norton, R. H.; Russell, J. M.

in Journal of Geophysical Research. Atmospheres (1987), 92(D10), 11951--11964

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See detailColumn abundance and the long-term trend of hydrogen chloride (HCl) above the Jungfraujoch Station
Zander, Rodolphe; Roland, G.; Delbouille, L.; Sauval, A.; Farmer, C. B.; Norton, R. H.

in Journal of Atmospheric Chemistry (1987), 5(4), 395-404

See detailIntercomparison of stratospheric NO2 and NO3 measurements during MAP/GLOBUS 1983
Pommereau, J. P.; Fabian, P.; Flentje, G.; Helten, M.; Pätz, H. W.; Ehhalt, D. H.; Karcher, F.; Froment, G.; Armand, G.; Matthews, W. A.; Offermann, D.; Rippel, H.; Rigaud, P.; Naudet, J. P.; Huguenin, D.; Simon, P. C.; Peetermans, W.; Vandeneede, P.; Zander, Rodolphe; Roland, G.

in Planetary and Space Science (1987), 35(5), 615-629

Nitrogen dioxide and trioxide have been observed from balloons, plane and from the ground during MAP/GLOBUS 1983. Comparison between NO2 mixing ratios measured from balloons shows some agreement between remote sensing techniques on the one hand and in situ methods on the other. The two sets of data which agree in the lower stratosphere at 20 km diverge at higher altitudes by a factor of 2 around 27 km and 4 around 33 km. The NO2 column densities observed at sunset from the ground are in agreement with plane and balloon determinations, provided that the average mixing ratio below 16 km was indeed lower than 1.5 × 10−10. The diurnal variation of the NO2 column as determined from ground observations during the second half of September differs from the one seen in the stratosphere. A first comparison between NO3 night-time remote measurement and preliminary in situ results show a disagreement by a factor of 2.

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See detailObservation of several chlorine nitrate (ClONO2) bands in stratospheric infrared spectra
Zander, Rodolphe; Rinsland, C. P.; Farmer, C. B.; Brown, L. R.; Norton, R. H.

in Geophysical Research Letters (1986), 13(8), 757--760

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See detailEvidence for the presence of the 802.7 cm−1 band Q branch of HO2NO2 in high resolution solar absorption spectra of the stratosphere
Rinsland, C. P.; Zander, Rodolphe; Farmer, C. B.; Norton, R. H.; Brown, L. R.; Russell, J. M.; Park, J. H.

in Geophysical Research Letters (1986), 13(8), 761--764

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See detailSpectroscopic detection of CH3Cl in the upper troposphere and lower stratosphere
Park, J. H.; Zander, Rodolphe; Farmer, C. B.; Rinsland, C. P.; Russell, J. M.; Norton, R. H.; Raper, O. F.

in Geophysical Research Letters (1986), 13(8), 765--768

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See detailDetection of carbonyl fluoride in the stratosphere
Rinsland, C. P.; Zander, Rodolphe; Brown, L. R.; Farmer, C. B.; Park, J. H.; Norton, R. H.; Russell, J. M.; Raper, O. F.

in Geophysical Research Letters (1986), 13(8), 769--772

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See detailOn the temporal increase of tropospheric CH4
Ehhalt, D. H.; Zander, Rodolphe; Lamontagne, R. A.

in Journal of Geophysical Research (1983), 88(C13), 8442--8446

The available data on the tropospheric CH4 mixing ratio in the northern hemisphere are examined for a possible trend, with the following result: There was no or little increase between 1948 and 1965 as evidenced by IR measurements of the atmospheric CH4 column density. Between 1965 and 1975 there appears a weak increase in tropospheric CH4 at an average rate of about 0.5%/yr, as suggested by independent sets of CH4 measurements. Between 1978 and 1980 a CH4 increase of 1 to 2%/yr has been observed by several laboratories. The overall trend resulting for the past 30 years is subject to a fair amount of uncertainty.

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See detailSimultaneous detection of FC-11, FC-12 and FC-22, through 8 to 13 Micrometers IR solar observations from the ground
Zander, Rodolphe; Stokes, Gerald M.; Brault, James W.

in Geophysical Research Letters (1983), 10(7), 521--524

High-resolution solar observations covering the 8 to 13 µm atmospheric window are now being carried out routinely at the Kitt Peak National Observatory (KPNO), Tucson, Arizona, using a 1 meter-path difference Fourier transform spectrometer. Such observations allow the simultaneous measurement of a large number of trace gases. Preliminary results for the three most important fluorocarbons, FC-11, FC-12 and FC-22 are reported here. These results, in the form of average mixing ratios, show the potential and illustrate the performance of the Kitt Peak interferometer for this application.

See detailDétection, par voie spectroscopique, de l’acétylène et de l’éthane dans l’atmosphère terrestre, à partir d’observations solaires infrarouges au sol
Zander, Rodolphe; Stokes, G.M.; Brault, J.W.

in Comptes Rendus de l'Académie des Sciences. Série 2, Sciences de la Terre et des Planètes (1982), 295

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See detailRecent observations of HF and HCl in the upper stratosphere
Zander, Rodolphe

in Geophysical Research Letters (1981), 8(4), 413--416

Concentrations of gas phase hydrofluoric- and hydrochloric acid have been determined in the upper stratosphere from near-infrared solar spectra recorded in the course of balloon fights from Palestine, Texas, USA (32°N latitude), in October 1978 and in September 1979. The average mixing ratios for HF deduced respectively from these flights are (4.8±.3)×10−10ppv above 30.3km and (6.2±.5)×10−10ppv above 36.8km. This observed difference is ascribed to an increase in the HF concentration out to at least 37km. The HCl mixing ratios deduced from the 1978 flight yield (4.5±.6)×10−10ppv at 21.7km, (7.5±.7)×10−10ppv at 27.5 km and (2.1±.4)×10−9ppv above 30.5km. Observations in 1979 imply an average HCl mixing ratio above 36.8km of (2.4±.4)×10−9ppv. Our data do not indicate a measurable temporal trend of the HCl concentration above 30km.

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See detailConcentration of carbon monoxide in the upper stratosphere
Zander, Rodolphe; Leclercq, H.; Kaplan, L. D.

in Geophysical Research Letters (1981), 8(4), 365--368

The concentration of telluric carbon monoxide has been determined in the upper stratosphere from infrared solar spectra recorded by balloon on October 1978 and September 1979, over Texas, USA. The average mixing ratios were found to be (2.1∓.3)×10−8ppv and (3.7∓.4)×10−8ppv above the float altitudes of 30.6 and 36.8 km, respectively. The concentration profile deduced from all our measurements indicates that the CO mixing ratio increases in the upper stratosphere, from (1∓.3)×10−8ppv at 30.6 km, to about 4×10−8ppv above 41 km.

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See detailConfirming the presence of hydrofluoric acid in the upper stratosphere
Zander, Rodolphe; Roland, G.; Delbouille, L.

in Geophysical Research Letters (1977), 4(3), 117--120

See detailIdentification of solar lines out to 8 microns, based on spectra obtained by balloon
Biémont, Emile; Zander, Rodolphe

in Astronomy and Astrophysics (1977), 56

See detailLa présence d’acide fluorhydrique dans la stratosphère confirmée par des observations à partir du sol
Zander, Rodolphe; Roland, G; Delbouille, L

in C.R. Acad. Sci. Paris (1977), 284

See detailHigh resolution infrared solar observations by balloon
Zander, Rodolphe

in Infrared Physics (1976), 16

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See detailWater vapor above 25 Km altitude
Zander, Rodolphe

in Pure and Applied Geophysics (1973), 106(1), 1346-1351

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See detailAdditional details on the near-infrared reflectivity of laboratory ice clouds
Zander, Rodolphe

in Journal of Geophysical Research (1968), 73(20), 6581--6584

See detailProjet d’observation du spectre infrarouge du soleil, à haute résolution, par ballons stratosphériques
Zander, Rodolphe; Delbouille, L; Roland, G

in Comptes-Rendus du colloque International du CNES "Utilisation des ballons pour la recherche scientifique ̎ (1967, July), II

See detailWater vapor in the stratosphere
Zander, Rodolphe; Bottema, Murk

in Journal of Geophysical Research (1967), 72(22), 5749--5751

See detailMoisture contamination at altitude by balloon and associated equipment
Zander, Rodolphe

in Journal of Geophysical Research (1966), 71(15), 3775--3778

See detailSpectral scattering properties of ice clouds and Hoarfrost
Zander, Rodolphe

in Journal of Geophysical Research (1966), 71(2), 375--378

See detailThe composition of the Venus clouds and implications for model atmospheres
Bottema, Murk; Plummer, William; Strong, John; Zander, Rodolphe

in Journal of Geophysical Research (1965), 70(17), 4401--4402

See detailComposition of the Clouds of Venus.
Bottema, Murk; Plummer, William; Strong, John; Zander, Rodolphe

in Astrophysical Journal (1964), 140