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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 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 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 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

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See detailAttempting to retrieve peroxyacetyl nitrate from ground-based infrared solar spectra
Mahieu, Emmanuel ULiege; Fischer, Emily V.; Tzompa-Sosa, Zitely A. et al

in Geophysical Research Abstracts (2018, April 09), 20

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

Poster (2017, December 13)

Ethane is the most abundant non-methane hydrocarbon (NMHC) in the Earth atmosphere. Its main sources are of anthropogenic origin, with globally 62% from leakage during production and transport of natural ... [more ▼]

Ethane is the most abundant non-methane hydrocarbon (NMHC) in the Earth atmosphere. Its main sources are of anthropogenic origin, with globally 62% from leakage during production and transport of natural gas, 20% from biofuel combustion and 18% from biomass burning. In the Southern hemisphere, anthropogenic emissions are lower which makes biomass burning emissions a more significant source. The main removal process is oxidation by the hydroxyl radical (OH), leading to a mean atmospheric lifetime of 2 months. Until recently, a prolonged decrease of its abundance has been documented, at rates of -1 to -2.7%/yr, with global emissions dropping from 14 to 11 Tg/yr over 1984-2010 owing to successful measures reducing fugitive emissions from its fossil fuel sources. However, subsequent investigations have reported on an upturn in the ethane trend, characterized by a sharp rise from about 2009 onwards. The ethane increase is attributed to the oil and natural gas production boom in North America, although significant changes in OH could also be at play.In the present contribution, we report the trend of ethane at 23 ground-based Fourier Transform Infrared (FTIR) sites spanning the 80ºN to 79ºS latitude range. Over 2010-2015, a significant ethane rise of 3-5%/yr is determined for most sites in the Northern Hemisphere, while for the Southern hemisphere the rates of changes are not significant at the 2-sigma uncertainty level. Dedicated model simulations by EMAC (ECHAM5/MESSy Atmospheric Chemistry; ~1.8×1.8 degrees) implementing various emission scenarios are included in order to support data interpretation. The usual underestimation of the NMHCs emissions in the main inventories is confirmed here for RCP85 (Representative Concentration Pathway Database v8.5). Scaling them by 1.5 is needed to capture the background levels of atmospheric ethane. Moreover, additional and significant emissions (~7 Tg over 2009-2015) are needed to capture the ethane rise in the Northern hemisphere. Attributing them to the oil and gas sector and locating them in North America allows EMAC to produce adequate trends in the Northern hemisphere, but not in the Southern hemisphere, where they are overestimated. Possible causes for this difference are discussed. [less ▲]

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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 ULiege; Bader, Whitney ULiege; Bovy, Benoît ULiege et al

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 ... [more ▼]

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. [less ▲]

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See detailObservation and simulation of ethane at 22 FTIR sites
Mahieu, Emmanuel ULiege; Franco, Bruno ULiege; Pozzer, Andrea et al

Conference (2017, May 30)

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See detailImpact of circulation changes on the long-term trend of stratospheric hydrogen fluoride at five NDACC stations
Prignon, Maxime ULiege; Bernath, P.F.; Blumenstock, T. et al

Poster (2017, May 29)

Hydrogen fluoride is mainly produced by the photolysis of anthropogenic source gases such as the chlorofluorocarbons (CFC), the hydrochlorofluorocarbons (HCFC) and the hydrofluorocarbons (HFC). These ... [more ▼]

Hydrogen fluoride is mainly produced by the photolysis of anthropogenic source gases such as the chlorofluorocarbons (CFC), the hydrochlorofluorocarbons (HCFC) and the hydrofluorocarbons (HFC). These families of species are known for contributing to ozone depletion and/or to the greenhouse effect. It is thus essential to regulate and monitor their emissions. Despite the fact that the Montreal protocol (1987) has succeeded to reduce and then suppress the CFC emissions, HF is still increasing in the stratosphere because of ongoing emissions of the HCFC and HFC substitution products. In the framework of the recent studies demonstrating the influence of stratospheric circulation changes on the trend of long-lived tracers (e.g. hydrogen chlorine), we decided to investigate the impact of these circulation changes on HF. To achieve this objective, the rates of changes over time of HF total/partial columns at various latitudes of the globe will be determined and critically discussed. Fourier Transform Infrared data produced at five NDACC sites (Kiruna – 68°N, Jungfraujoch – 46°N, Izana – 28°N, Lauder 45°S and Arrival-heights – 78°S) and satellite data (HALOE and ACE) will be used for this study. This preliminary selection of ground-based stations allows to cover both hemispheres and our period of investigation (last two decades). Finally, in order to support our data interpretation, two SLIMCAT simulations (standard and fixed dynamics) will also be included. [less ▲]

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See detailThe recent increase of atmospheric methane from 10 years of ground-based NDACC FTIR observations since 2005
Bader, Whitney ULiege; Bovy, Benoît ULiege; Conway, Stephanie et al

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 ... [more ▼]

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. [less ▲]

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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 et al

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 ... [more ▼]

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. [less ▲]

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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 ULiege; Mahieu, Emmanuel ULiege; Vollmer, M. K. et al

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 ... [more ▼]

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. [less ▲]

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See detailDiurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N
Franco, Bruno ULiege; Marais, Eloise A.; Bovy, Benoît ULiege et al

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 ... [more ▼]

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. [less ▲]

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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 ULiege; Lejeune, Bernard ULiege; Bovy, Benoît ULiege et al

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 ... [more ▼]

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. [less ▲]

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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. et al

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 ... [more ▼]

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). [less ▲]

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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 ULiege; Hendrick, François; Van Roozendael, Michel et al

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 ... [more ▼]

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. [less ▲]

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