References of "Mahieu, Emmanuel"
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See detailImpacts of H2O variability on accuracy of CH4 observations from MIPAS satellite over tropics
Yirdaw Berhe, T.; Mengistu Tsidu, G.; Blumenstock, T. et al

in Atmospheric Measurement Techniques. Papers in Open Discussion (2019), 2019

Uncertainties of tropical methane concentrations, retrieved from spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), MIPAS version V5R_CH4_220 are large. We explore ... [more ▼]

Uncertainties of tropical methane concentrations, retrieved from spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), MIPAS version V5R_CH4_220 are large. We explore the relation of these uncertainties with water vapour variability. We further show that these uncertainties have been reduced in MIPAS version V5R_CH4_224. Coincident measurements of CH4 by MIPAS, ground based FTIR and CH4 derived from EOS MLS coincident measurements of atmospheric water vapour (H2O), carbon monoxide (CO) and nitrous oxide (N2O) are used to estimate the standard uncertainty of MIPAS CH4 220, MIPAS CH4 224 and natural variability of H2O. Different methods such as bias evaluation, differential method and correlation coefficient are employed to explore the latitudinal variations of standard uncertainty of MIPAS CH4 220 and natural variability of water vapour as well as its reduction on MIPAS CH4 224. The averaged bias between MIPAS CH4 220 and ground-based FTIR measurements are −12.3 %, 8.4 % and 1.2 % for tropics, mid-latitudes and high latitudes, respectively. The standard deviations of the differences for these latitudinal bands are 5.9 %, 4.8 % and 4.7 %. More-over, the correlation coefficient between MIPAS CH4 220 and MIPAS V5R_N2O_220 is 0.32 in the upper troposphere and lower stratosphere over tropics and larger than the mod-est value 0.5 in mid and high latitudes. The poor correlation between MIPAS CH4 220 and MIPAS N2O 220 over tropics can indicate the large uncertainty of MIPAS CH4 220 over tropics that is related to water variability. Similarly, mean relative difference between MIPAS CH4 224 and ground-based FTIR measurements are 3.9 %, −2.6 % and −2.7 % in altitude 15–21 km and the average estimated uncertainty of MIPAS CH4 224 methane were obtained 2.4 %, 1.4 % and 5.1 % in altitude ranges of 15 to 27 km for tropics, mid and high latitudes, respectively. The estimated measurement uncertainty of MIPAS CH4 224 is different for the three latitude bands in the northern hemisphere, reflecting the latitudinal variation of uncertainties of MIPAS methane. However, the large reduction of uncertainty in MIPAS CH4 224 as compared to MIPAS CH4 220 has been confirmed for the tropical measurements. The correlation coefficients between the uncertainty of MIPAS CH4 220 and the variability of water vapour in lower stratosphere are strong (0.88) on monthly temporal scales. Similar methods were used for MIPAS CH4 224. It was found that the uncertainty in methane due to the variability of water vapor has been reduced. [less ▲]

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See detailPost-peak trend of upper stratospheric hydrogen chloride derived from ground-based FTIR solar spectra and model simulations
Mahieu, Emmanuel ULiege; Prignon, Maxime ULiege; Servais, Christian ULiege et al

Conference (2019, May 23)

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented ... [more ▼]

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented, characterized by short-term variability which was attributed to atmospheric circulation changes, affecting mainly the lower stratosphere (Mahieu et al., 2014). This notably led to a temporary increase of HCl over 2007-2011, complicating the determination of the long-term HCl trend and the accurate verification of the success of the Montreal Protocol for the protection of the stratospheric ozone layer. Studies have used other long-lived tracers to remove the effects of dynamical variability in the lower stratosphere (e.g., Stolarski et al., 2018), while other investigations have suggested that trends in the upper stratosphere were potentially more appropriate for the long-term characterization of the HCl decrease (e.g., Froidevaux et al., 2015; Bernath and Fernando, 2018), especially when dealing with satellite height-resolved data. In this contribution, we use FTIR (Fourier Transform InfraRed) data from the Jungfraujoch station (Swiss Alps, 3580 m a.s.l.), a site of the NDACC network (http://www.ndacc.org), to study the evolution of HCl in some detail. The SFIT-4 retrieval algorithm implementing the Optimal Estimation Method of Rodgers (2000) is employed, providing HCl columns with good sensitivity from the tropopause up to about 40 km altitude. Moreover, the vertical resolution is sufficient to determine independent partial columns for the lower and upper stratosphere. With the support of model simulations performed with the 3D-Chemistry Transport Model of the Belgian Assimilation System for Chemical ObsErvations (BASCOE; Chabrillat et al., 2018), driven by the ERA-Interim meteorological reanalysis, we investigate the post-peak trend of HCl in the lower and upper stratosphere. We also determine the magnitude of the uncertainties affecting the various trends, using bootstrap tools which are specifically developed to take into account the auto-correlation present in our geophysical data sets. [less ▲]

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See detailPOst-peak trend of upper stratospheric hydrogen chloride derived from ground-based FTIR solar spectra and model simulations
Mahieu, Emmanuel ULiege; Prignon, Maxime ULiege; Servais, Christian ULiege et al

Conference (2019, April 12)

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented ... [more ▼]

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented, characterized by short-term variability which was attributed to atmospheric circulation changes, affecting mainly the lower stratosphere (Mahieu et al., 2014). This notably led to a temporary increase of HCl over 2007-2011, complicating the determination of the long-term HCl trend and the accurate verification of the success of the Montreal Protocol for the protection of the stratospheric ozone layer. Studies have used other long-lived tracers to remove the effects of dynamical variability in the lower stratosphere (e.g., Stolarski et al., 2018), while other investigations have suggested that trends in the upper stratosphere were potentially more appropriate for the long-term characterization of the HCl decrease (e.g., Froidevaux et al., 2015; Bernath and Fernando, 2018), especially when dealing with satellite height-resolved data. In this contribution, we use FTIR (Fourier Transform InfraRed) data from the Jungfraujoch station (Swiss Alps, 3580 m a.s.l.), a site of the NDACC network (http://www.ndacc.org), to study the evolution of HCl in some detail. The SFIT-4 retrieval algorithm implementing the Optimal Estimation Method of Rodgers (2000) is employed, providing HCl columns with good sensitivity from the tropopause up to about 40 km altitude. Moreover, the vertical resolution is sufficient to determine independent partial columns for the lower and upper stratosphere. With the support of model simulations performed with the 3D-Chemistry Transport Model of the Belgian Assimilation System for Chemical ObsErvations (BASCOE; Chabrillat et al., 2018), driven by the ERA-Interim meteorological reanalysis, we investigate the post-peak trend of HCl in the lower and upper stratosphere. We also determine the magnitude of the uncertainties affecting the various trends, using bootstrap tools which are specifically developed to take into account the auto-correlation present in our geophysical data sets. [less ▲]

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See detailInvestigation of stratospheric circulation using long-lived tracers with WACCM, BASCOE CTM and a reanalysis of MLS observations
Minganti, Daniele ULiege; Chabrillat, Simon; Christophe, Yves et al

Poster (2019, April 12)

The stratospheric circulation is investigated using WACCM4 (Whole Atmosphere Community Climate Model version 4), together with BASCOE CTM (Belgian Assimilation System for Chemical Observations Chemistry ... [more ▼]

The stratospheric circulation is investigated using WACCM4 (Whole Atmosphere Community Climate Model version 4), together with BASCOE CTM (Belgian Assimilation System for Chemical Observations Chemistry-Transport Model) and a reanalysis of stratospheric composition observed by MLS: BRAM2 (BASCOE Reanalysis of AURA MLS release 2) over the period 2005-2015. Three different reanalyses of the wind fields (ERA-interim, JRA55 and MERRA2) are used to drive the CTM, providing an estimate of the uncertainties in our representation of the actual stratospheric circulation. We use a long-lived tracer (N2O), and the Transformed Eulerian Mean (TEM) framework to analyse the tracer budget. We focus on the residual advection (mainly vertical) and eddy mixing (mainly horizontal) contributions to the N2O variations, studying the mean annual cycle and variability in the higher stratosphere and how it is depicted in the different datasets. The BRAM2 mean annual cycle, for both the vertical and the horizontal terms, is nearly in the middle of the spread. WACCM is in good agreement concerning the vertical term but differs considerably from the other datasets in the horizontal (~mixing) term. WACCM present a smaller variability with respect to the reanalysis in the Tropical higher stratosphere, especially for the vertical term. The next step of our research is to perform such analysis with the newer version of WACCM (version 6) as well as new BASCOE CTM runs using other reanalysis products. Multi-decadal changes in the terms of the budget, and their space dependence, will be investigated as well. [less ▲]

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See detailImpact of lower stratospheric dynamical variability on total inorganic fluorine derived from ground-based FTIR, satellite and model data
Prignon, Maxime ULiege; Bernath, P. F.; Chabrillat, S. et al

Poster (2019, April 12)

Long-lived tracer concentrations in the lower stratosphere are affected by short time scale circulation variability as highlighted by recent papers (e.g., Mahieu et al., 2014). Many tracers, such as ... [more ▼]

Long-lived tracer concentrations in the lower stratosphere are affected by short time scale circulation variability as highlighted by recent papers (e.g., Mahieu et al., 2014). Many tracers, such as hydrogen chloride (HCl) or hydrogen fluoride (HF) have now been successfully used to investigate or identify this variability (e.g., Harrison et al., 2016) In this work, the main reservoirs of inorganic fluorine [i.e., HF, carbonyl fluoride (COF2) and carbonyl chloride fluoride (COClF)] and their sum (total inorganic fluorine, Fy) are used to investigate the lower stratospheric circulation changes. We use Fourier Transform InfraRed (FTIR) ground-based observations conducted in the framework of the NDACC network (http://www.ndacc.org) to derive column abundances of HF and COF2, thus providing a good proxy for Fy. To support this research, we also include satellite observations from HALOE (HF available) and ACE-FTS (HF, COF2 and COClF available). Moreover, we use the Chemical-Transport Model (CTM) BASCOE (Belgian Assimilation System for Chemical ObsErvations; Chabrillat et al., 2018) to evaluate the representation of the investigated circulation changes in state-of-the-art meteorological reanalyses. We also evaluate if WACCM4 (Whole Atmosphere Community Climate Model version 4) is able to reproduce these changes through a free dynamics and free chemistry run. Finally, SLIMCAT CTM (Chipperfield et al., 2015) simulations are included to provide information on the partitioning between the main Fy reservoirs. [less ▲]

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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 ULiege; Chabrillat, Simon; Minganti, Daniele ULiege et al

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 ... [more ▼]

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. [less ▲]

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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 et al

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 ... [more ▼]

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. [less ▲]

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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 et al

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

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See detailFirst results from the KinAero MAXDOAS instrument
Pinardi, Gaia; Alexis, Merlaud; Martina, Friedrich et al

in Geophysical Research Abstracts (2019), Vol. 21(EGU2019-15792-1, 2019), 1

As part of an ongoing collaboration with the University of Kinshasa (RDC), we have recently developed a compact low-cost MAXDOAS instrument (KinAero) in view of deploying it at Kinshasa for long term ... [more ▼]

As part of an ongoing collaboration with the University of Kinshasa (RDC), we have recently developed a compact low-cost MAXDOAS instrument (KinAero) in view of deploying it at Kinshasa for long term monitoring of atmospheric pollutants such as NO2 and HCHO. We present the KinAero system, which consists in a compact grating spectrometer from the Avantes company coupled by optical fiber to an elevation scanning device operating in one fixed azimuthal direction. The spectral range covers the wavelengths from 290-550 nm with a resolution of 0.7 nm FWHM. We show characterization results of KinAero from the lab (detector linearity, signal-to-noise, pointing accuracy,...) and assess the overall quality of the NO2 and O4 slant column measurements based on comparisons with the BIRA-IASB NDACC-certified MAXDOAS instrument in Uccle. Between September and December 2018, KinAero was installed on the ICOS observation tower in Vielsalm (50.31◦N, 6◦E, 445 m.a.s.l), in a forest area. These measurements were performed as part of the BelAIR-Silva campaign, which provided a good opportunity to test the instrument in the field for a period of several months. The instrument was found to be stable during the full duration of the campaign. Using retrieval tools developed as part of the ESA FRM4DOAS project, we derived time-series of NO2 and HCHO column and profile measurements, which are applied to comparisons with the TROPOMI/S5P satellite instrument. [less ▲]

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See detailAnalysis of trends in total stratospheric ozone
Salawitch, Ross J; Tribett, W R; Wales, P et al

Conference (2018, December 12)

Time series of total column ozone have exhibited unusual, unexpected behavior over the past few years. In year 2016, total ozone was lower than expected based on some forecasts that utilize the time ... [more ▼]

Time series of total column ozone have exhibited unusual, unexpected behavior over the past few years. In year 2016, total ozone was lower than expected based on some forecasts that utilize the time evolution of equivalent effective stratosphere chlorine (EESC). Conversely, total column ozone exhibited a sharp rise in 2017. The existence of a new formulation (i.e., Engel et al., ACP, 2017) for the fractional release factors (FRFs) used to find EESC for mid-latitude lower stratospheric air parcels, the contribution of very short-lived chlorine and bromine compounds to EESC, as well as possible temporal variations in tropospheric column ozone compound the difficulty in establishing a quantitative relationship between the time evolution of EESC and stratospheric ozone. This presentation will consist of an analysis of the ~40 year record of total column ozone measured from space (e.g., version 8.6 of the NASA SBUV Merged Ozone Data Set at the time of abstract submission), along with: a) stratospheric chlorine loading from various satellite instruments as well as the long-term ground-based measurement from Jungfraujoch, Switzerland; b) various other quantities that affect the long-term evolution of stratospheric ozone (e.g., total solar irradiance, stratospheric optical depth, quasi-biennial oscillation of the direction of tropical stratospheric winds) c) estimates of tropospheric column ozone to assess our understanding of trends in total stratospheric ozone. Preliminary results indicate better quantitative understanding is attained for the new FRFs, which lead to a more gradual recovery of total stratospheric ozone than is found using the old FRFs. Reference: Engel, A. et al., ACP, 18, 601619, doi:10.5194/acp-18-601-2018, 2018. [less ▲]

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See detailUpdate on the FTIR monitoring program at the Jungfraujoch station
Mahieu, Emmanuel ULiege; Prignon, Maxime ULiege; Servais, Christian ULiege

Scientific conference (2018, October 31)

We present a report on the status of the FTIR monitoring program at the Jungfraujoch station. Focus is put on the reanalysis of the HCFC-22 (CHClF2) time series and to our first attempt to retrieve PAN ... [more ▼]

We present a report on the status of the FTIR monitoring program at the Jungfraujoch station. Focus is put on the reanalysis of the HCFC-22 (CHClF2) time series and to our first attempt to retrieve PAN from ground-based infrared solar absorption spectra. [less ▲]

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See detailObserving the atmospheric evolution of ozone-depleting substances
Reimann, Stefan; Elkins, James W.; Fraser, Paul J. et al

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 ... [more ▼]

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. [less ▲]

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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. et al

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 ... [more ▼]

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. [less ▲]

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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. et al

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 ... [more ▼]

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. [less ▲]

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See detailThe influence of biomass burning on the Arctic: Pan-Arctic FTIR observations and model results
Strong, K; Lutsch, E; Conway, S et al

Poster (2018, September)

Transport of biomass burning emissions into the Arctic can cause episodic enhancements of multiple trace gas species. We present a multi-year time series of the total columns of carbon monoxide (CO ... [more ▼]

Transport of biomass burning emissions into the Arctic can cause episodic enhancements of multiple trace gas species. We present a multi-year time series of the total columns of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) measured using Fourier Transform Infrared (FTIR) solar absorption spectroscopy at six high-latitude sites: Eureka, Nunavut; Ny Alesund, Norway; Thule, Greenland; Kiruna, Sweden; Poker Flat, Alaska; and St. Petersburg, Russia, and at three mid-latitude sites; Zugspitze, Germany; Jungfraujoch, Switzerland; and Toronto, Ontario. For each site, the inter-annual trends and seasonal variabilities of the CO total column time series are determined and enhancements above ambient levels are used to identify possible wildfire pollution events. Correlations of HCN and C2H6 with CO, back-trajectories from HYSPLIT and FLEXPART, and fire locations from the Moderate Resolution Spectroradiometer (MODIS) confirm the detections and identify the source regions. The GEOS-Chem chemical transport model is run in tagged mode to determine the relative contributions to the observed enhancements from continental-scale biomass burning source regions. Exceptional emissions of CO, HCN, C2H6, and ammonia (NH3) from the 2017 North American wildfires were measured at Eureka and Thule, indicating that wildfires may be a major source of NH3 in the summertime high Arctic. The enhancement ratios of the long-lived species HCN and C2H6 are found to be comparable between sites, but for NH3, the enhancement ratios are strongly dependent on the transport patterns of the smoke plumes. Satellite measurements of NH3 from the Infrared Atmospheric Sounding Instrument (IASI) and Cross-track Infrared Sounder (CrIS) are used to examine the spatial and temporal variabilities of NH3. Comparisons to a high-resolution (0.25° x 0.3125°) nested run of GEOS-Chem using emissions from the Global Fire Assimilation System (GFAS) are performed to evaluate the emission inventories and assess the long-range transport of NH3 to the high Arctic. [less ▲]

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See detailMesure et surveillance de constituants atmosphériques chlorés à la station du Jungfraujoch en support au Protocole de Montréal pour la protection de l'ozone stratosphérique
Mahieu, Emmanuel ULiege

Poster (2018, September)

Nous présentons de manière synthétique les contributions des chercheurs liégeois à la surveillance de l'abondance du chlore -destructeur de la couche protectrice d'ozone stratosphérique- dans l’atmosphère ... [more ▼]

Nous présentons de manière synthétique les contributions des chercheurs liégeois à la surveillance de l'abondance du chlore -destructeur de la couche protectrice d'ozone stratosphérique- dans l’atmosphère de la terre ainsi qu'à la compréhension de son évolution au cours des dernières décennies. [less ▲]

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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. et al

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 ... [more ▼]

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. [less ▲]

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See detailObservation and simulation of ethane (C2H6) at 23 FTIR sites
Mahieu, Emmanuel ULiege; Franco, B.; Pozzer, A. et al

in Geophysical Research Abstracts (2018, April 11), 20

Detailed reference viewed: 34 (9 ULiège)