References of "Duchatelet, Pierre"
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See detailRetrievals of C2H2 from high-resolution FTIR solar spectra recorded at the Jungfraujoch station (46.5ºN) and comparison with ACE-FTS observations
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Bernath, P. F. et al

in Geophysical Research Abstracts (2008), 10

Acetylene (C2H2) is among the nonmethane hydrocarbons (NMHCs) accessible to infrared remote sensing technique. As a product of combustion and biomass burning, it is emitted at the Earth’s surface and ... [more ▼]

Acetylene (C2H2) is among the nonmethane hydrocarbons (NMHCs) accessible to infrared remote sensing technique. As a product of combustion and biomass burning, it is emitted at the Earth’s surface and further transported and mixed into the troposphere. Destruction by OH is the main removal process. The average tropospheric lifetime of C2H2 is estimated at about 1 month on the global scale; at mid-latitudes, it varies between 20 days in summer to 160 days in winter. This compound is appropriate to study tropospheric pollution and transport, and is often used in conjunction with other tracers of fires. C2H2 presents exploitable infrared absorption features near 3 and 15 μm, where weak isolated lines of the nu5 and the nu2 + nu4 + nu5 bands are found, respectively. Several of these lines can be used to retrieve abundances of C2H2 from high-resolution groundbased infrared solar spectra. Typical observations recorded at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580m asl, Swiss Alps) by the NDACC (Network for the Detection of Atmospheric Composition Change)-affiliated Bruker instrument have been fitted with the OEM-SFIT-2 (v3.91) algorithm. Various approaches and combination of lines have been tested, seeking for the optimum inversion strategy. The HITRAN-2004 spectroscopic line parameters including the August 2006 updates for water vapor have been adopted in the retrievals. These approaches will be presented and critically compared, with the help of error budget and information content analyses, taking into account the impact of major interferences such as water vapor. The time series of C2H2 tropospheric column abundances above Jungfraujoch will also be presented, including determination of its long-term trend and strong seasonal cycle. The ground-based results will further be compared with zonal mean observations performed by the ACE-FTS space-based instrument since early 2004. [less ▲]

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See detailImpact of different spectroscopic datasets on CH4 retrievals from Jungfraujoch FTIR spectra
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

(2008)

Due to its high warming potential and its relatively long chemical lifetime (~9 years), atmospheric methane (CH4) plays a major role in the radiative forcing responsible of the greenhouse effect. Methane ... [more ▼]

Due to its high warming potential and its relatively long chemical lifetime (~9 years), atmospheric methane (CH4) plays a major role in the radiative forcing responsible of the greenhouse effect. Methane also affects climate by influencing tropospheric ozone and stratospheric water. High quality methane data sets are needed to understand its cycle and evaluate its budget of sources and sinks. Methane vertical distribution as well as total and partial column time series can be retrieved from high-resolution ground-based FTIR spectra, using, e.g., the SFIT-2 algorithm which implements the Optimal Estimation Method of Rodgers . However, although several retrieval approaches characterized by relatively high information content exist, methane retrieved profiles very often present large oscillations in their tropospheric range, which might result partly from inappropriate or inconsistent parameters. Significant improvements on retrieval quality should therefore be reached by using more accurate or compatible CH4 spectroscopic data. The main purpose of this contribution is to test and compare three different sets of CH4 spectroscopic parameters and to quantify their impact on CH4 retrieved products as well as on the fitting quality. [less ▲]

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See detailObservations of CH4, CH3D and H2CO at Ile de La Réunion from ground-based FTIR and MAXDOAS campaign measurements
Vigouroux, Corinne; De Mazière, Martine; Van Roozendael, Michel et al

Poster (2007, November)

Ile de La Réunion (21°S, 55°E) is candidate to become a primary station the ground-based Network for the Detection of Atmospheric Composition Change (NDACC) which was formed to provide long-term ... [more ▼]

Ile de La Réunion (21°S, 55°E) is candidate to become a primary station the ground-based Network for the Detection of Atmospheric Composition Change (NDACC) which was formed to provide long-term monitoring of atmospheric trace gases at globally distributed sites. Ground-based network data are also very valuable for the validation of satellite data, such as SCIAMACHY, ACE-FTS and IASI. Up to now, only a few NDACC stations are located in the Southern Hemisphere, and none of them is at subtropical latitude. Three campaigns of FTIR measurements were made at the Ile de La Réunion in preparation of a near future permanent installation, namely in October 2002, from August to October 2004, and from May to November 2007. A UV-visible Multi-Axis DOAS (MAXDOAS) instrument was operated at the same site from July 2004 to June 2005. The inversion algorithms for both the MAXDOAS and FTIR spectral data analyses use the Optimal Estimation Method to derive information about the vertical distribution of the target gases. We will present the vertical profiles and total columns of the greenhouse gas CH4 and its isotopologue CH3D, obtained from the FTIR measurements. For the latter, the number of degrees of freedom for signal is close to one, limiting the information to the total column abundance. Early comparisons with correlative measurements from satellite data will be discussed. Formaldehyde (H2CO) is a source of HOx and an indicator for biogenic emissions, biomass burning, and anthropogenic pollution. It can be measured by both the FTIR and UV-Visible MAXDOAS instruments. The total columns obtained by the two techniques in the common period of measurements August-October 2004 will be discussed. We will also show the comparisons of the time series for formaldehyde from both instruments with correlative SCIAMACHY data above La Réunion. [less ▲]

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See detailRecent evolution of stratospheric inorganic chlorine (Cly) inferred from long-term ground-based FTIR observations of HCl and ClONO2
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Zander, Rodolphe ULg et al

in Geophysical Research Abstracts (2007, May 02), 9

Over the past decades, the increase of the stratospheric inorganic chlorine (Cly) loading has been the major cause for the ozone layer depletion, a matter of particular concern because of its ... [more ▼]

Over the past decades, the increase of the stratospheric inorganic chlorine (Cly) loading has been the major cause for the ozone layer depletion, a matter of particular concern because of its anthropogenic nature. Fortunately, appropriate decisions have been defined and put into force at the international level, leading to regulations adopted within the frame of the Montreal Protocol and its Amendments and Adjustments, and aiming at the suppression of all chlorine-bearing source gas emissions. Since its formalization, the NDSC (Network for Detection of Stratospheric Change, recently renamed NDACC, Network for the Detection of Atmospheric Composition Change) has given high priority to the monitoring of Cly based on solar observations with Fourier transform infrared (FTIR) spectrometers operated at the ground. Within this context, high-resolution solar absorption spectra recorded at Northern and Southern mid-latitudes have been analyzed to retrieve total vertical column abundances of the two main inorganic chlorine species, i.e. HCl and ClONO2. At these latitudes and in the absence of chlorine activation, these two reservoirs account for more than 92% of the total Cly loading. In this contribution, column abundance time series of HCl and ClONO2 for both the Jungfraujoch (46.5°N) and Lauder (45°S) NDACC primary stations will be presented. Comparison of these measurements with the 3-D CTM KASIMA model predictions will be shown and discussed critically, with some focus on the time period following the peak loading. Related trends will be determined and compared to expectations deduced from the most recent emission scenarios. [less ▲]

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See detailRetrievals of HCN from high-resolution FTIR solar spectra recorded at the Jungfraujoch station
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Demoulin, Philippe ULg et al

in Geophysical Research Abstracts (2007, April)

Recent investigations have resulted in the revision of the lifetime of hydrogen cyanide (HCN) from 2.5 years to 2-5 months, more in line with its important and well documented variability in the ... [more ▼]

Recent investigations have resulted in the revision of the lifetime of hydrogen cyanide (HCN) from 2.5 years to 2-5 months, more in line with its important and well documented variability in the troposphere. The main HCN source is believed to be biomass burning, making this species a useful tracer of fires, e.g. the widespread and intense 2004 boreal fires. Oxidation by the OH radical is among the identified sinks, while uptake by oceans has been hypothesized as the dominant sink. As shown by previous investigations, several lines from the nu3 fundamental HCN band at 3 μm can be used to retrieve information on vertical distribution of hydrogen cyanide from high-resolution FTIR solar absorption spectra. The major interfering gas in this region is water vapor. A series of typical observations recorded at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580m asl, Swiss Alps) by the NDACC (Network for the Detection of Atmospheric Composition Change)-affiliated Bruker instrument have been fitted using various approaches to determine the optimum strategy to be used for HCN retrievals at that site, even under very wet conditions. The selected approach is made of 7 windows encompassing 5 HCN lines. The a priori information (HCN vertical distribution and covariance matrix) is based on ACE-FTS measurements performed over northern midlatitudes. The HITRAN-2004 spectroscopic line parameters including the August 2006 updates for water vapor have been adopted in the retrievals performed with the OEM-SFIT-2 (v3.91) algorithm. This contribution will give a full description of the adopted retrieval approach, including error budget and information content analysis. Tropospheric column time series of HCN from 1994 onwards will also be presented and discussed. [less ▲]

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See detailMeasured and modelled trends of stratopsheric Cly and Fy column amounts in the northern hemisphere
Ruhnke, Roland; Blumenstock, Thomas; Duchatelet, Pierre ULg et al

Poster (2007, April)

Reactive inorganic chlorine plays a crucial role in the stratospheric ozone depletion. To stabilize and enable a recovering of the stratospheric ozone layer, the Montreal protocol and its amendments and ... [more ▼]

Reactive inorganic chlorine plays a crucial role in the stratospheric ozone depletion. To stabilize and enable a recovering of the stratospheric ozone layer, the Montreal protocol and its amendments and adjustments have been progressively implemented to reduce or even stop the production and emission of important chlorinated source gases (CFCs, HCFCs, CCl4, CH3CCl3, and Halons). As these source gases are photolysed in the stratosphere into inorganic chlorine and fluorine, respectively, the turn over of the inorganic chlorine (HCl and ClONO2) and slowing down of fluorine (HF and COF2) reservoirs act as a verification of the effectiveness of these protocols. Here we present results of long-term measurements of the stratospheric column of HCl, ClONO2, and HF obtained at different stations in the northern hemisphere (Ny Alesund, Kiruna, Zugspitze, Jungfraujoch, Izana, all affiliated to the NDACC, Network for the Detection of Atmospheric Composition Change) within the PEP (Pole- Equator-Pole) network. These time series are interpreted with model calculations performed with a state of the art 2-D model and the 3-D CTM KASIMA with respect to the determination of the slowing down or turn over, respectively. In addition, trend parameters calculated using different approaches (e.g. linear trend, bootstrap-method) will be presented and intercompared. [less ▲]

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See detailApproaches for retrieving abundances of methane isotopologues in the frame of the AGACC project from ground-based FTIR observations performed at the Jungfraujoch
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

Poster (2007, April)

This work has been performed within the frame of AGACC(http://www.oma.be/AGACC/Home.html), a contribution to the Belgian Scientific Support for a Sustainable Development. The project intends to make an ... [more ▼]

This work has been performed within the frame of AGACC(http://www.oma.be/AGACC/Home.html), a contribution to the Belgian Scientific Support for a Sustainable Development. The project intends to make an advanced exploitation of existing ground-based remote-sensing measurements for a selection of atmospheric species that play an important role in the chemistry of the atmosphere and that have a direct or indirect impact on climate. Target species include -among others- lower tropospheric aerosols, H2O, HDO, CH4, HCN and CO. The instrumentation includes 3 types of spectrometers (FTIR, MAXDOAS and Brewer) and one CIMEL sun photometer. These instruments are operated at 3 different sites (Jungfraujoch, Ile de la Réunion and Uccle) and most of them are affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC, formerly NDSC - http://www.ndacc.org), a group dedicated to performing high-quality long-term observations. This contribution will deal with the detection of the isotopologues of methane, a species released to the atmosphere by natural processes (e.g. wetlands, termites) as well as by anthropogenic activities (e.g. fossil fuel exploitation, rice agriculture, biomass burning, etc). Due to its high warming potential and its relatively long chemical lifetime, atmospheric methane is a major greenhouse gas. Methane also affects climate by influencing tropospheric ozone and stratospheric water. The cycle of methane is complex and a thoroughly study of the sources and sinks of its main isotopologue, as well as the other isotopic species, is necessary to characterize it. Isotopic ratios are also useful to differentiate between various sources of atmospheric methane. To study the vertical distribution of methane isotopologues from the high resolution FTIR spectra recorded by the University of Liège instrument at the International Scientific Station of the Jungfraujoch (ISSJ; 46.5°N, 8.0°E, 3580m a.s.l., Swiss Alps), we have selected several 13CH4 lines distributed in the so-called InSb (1-5 µm) and MCT (2-16 µm) spectral ranges. A set of four microwindows has also been selected for the study of CH3D. Using the SFIT-2 v3.91 algorithm, vertical column abundances as well as low-resolution vertical distributions have been retrieved, adjusted from an a priori profile defined on a 41 layers scheme and derived from ACE-FTS space observations. The information content and first preliminary retrieval results will be presented. [less ▲]

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See detailDetermination of COF2 vertical distributions above Jungfraujoch by FTIR and multi-spectra fitting
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

Poster (2007, April)

The major sources of fluorine in the stratosphere are CFC-11 and CFC-12. Photolysis of these compounds leads to release of chlorine atoms, while the fluorine is, in a first step, present in the form of ... [more ▼]

The major sources of fluorine in the stratosphere are CFC-11 and CFC-12. Photolysis of these compounds leads to release of chlorine atoms, while the fluorine is, in a first step, present in the form of carbonyl compounds like COClF and COF2. Their further photolysis liberates fluorine atoms, which are quickly converted to HF. Given its long life time, COF2 is the second stratospheric fluorine reservoir. The first COF2 vertical distributions were derived from occultation measurements performed by the ATMOS instrument during the SPACELAB-3 Space Shuttle mission in 1985. The Canadian FTIR spectrometer ACE-FTS, onboard the SCISAT-1 satellite, is the first instrument since the last ATMOS flight in 1994, to record COF2 vertical profiles from space. All these observations show that, at mean latitudes, COF2 concentration is maximum between 30 and 35 km. Several COF2 IR absorption lines located either in the so-called InSb (1-5 µm) and MCT (2-16 µm) spectral ranges can be used to determine its total column from ground-based FTIR observations. In this context, several studies concerning the evolution of COF2 total column above various stations were published during the nineties. At this time, no study concerning the inversion of COF2 vertical distributions from ground-based FTIR spectra has been published. This report deals with the feasibility of such inversions, using, simultaneously, via the SFIT-2 v3.91 algorithm, a multi-microwindows and a multi-spectra fitting procedure. The multi-spectra method consists of combining several FTIR observations, recorded during the same day, to increase the information content. A selection of microwindows in InSb and MCT ranges, a complete discussion about the data characterization (e.g. information content) and typical examples of COF2 retrieved profiles from high resolution solar spectra recorded with the University of Liège Jungfraujoch FTS will be revealed. [less ▲]

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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 et al

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 ... [more ▼]

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. [less ▲]

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See detailFTIR Observations at the Jungfraujoch Station for long-term monitoring of the Troposphere and Validation of the Space-based Sensors.
Mahieu, Emmanuel ULg; Zander, Rodolphe ULg; Demoulin, Philippe ULg et al

in Burrows, J.; Borrell, P. (Eds.) Measuring Tropospheric Trace Constituents from Space. (2007)

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See detailOptimisation of retrieval strategies using Jungfraujoch high-resolution FTIR observations for long-term trend studies and satellite validation.
Mahieu, Emmanuel ULg; Servais, Christian ULg; Duchatelet, Pierre ULg et al

in Burrows, J.; Borrell, P. (Eds.) Observing Tropospheric Trace Constituents from Space. (2007)

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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. et al

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 ... [more ▼]

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. [less ▲]

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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 et al

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 ... [more ▼]

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. [less ▲]

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See detailEvolution of a dozen non-CO2 greenhouse gases above Central Europe since the mid-1980s.
Zander, Rodolphe ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

in Proceedings of the 4th International Symposium on Non-CO2 Greenhouse Gases (2006)

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See detailAdvanced exploitation of ground-based Fourier transform infrared observations for tropospheric studies over Europe: achievements of the UFTIR project
De Mazière, Martine; Vigouroux, Corinne; Blumenstock, Thomas et al

in Geophysical Research Abstracts (2006), 8

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including information about their vertical ... [more ▼]

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including information about their vertical distributions in the troposphere and the stratosphere. Such observations have regularly been made since many years as a contribution to the NDSC (Network for the Detection of Stratospheric Change). They are the only ground-based remote sensing observations available nowadays that carry information about key atmospheric trace species in the free troposphere, among which the most important greenhouse gases. The European UFTIR project (Time series of Upper Free Troposphere observations from a European ground-based FTIR network, http://www.nilu.no/uftir) has focused on maximizing the information content of FTIR long-term monitoring data of some direct and indirect greenhouse gases (CH4, N2O, O3,HCFC-22, and CO and C2H6, respectively). The UFTIR network includes six NDSC stations in Western Europe, covering 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 of the abovementioned target gases. A bootstrap resampling method has been implemented to evaluate trends of the tropospheric and total burdens of the target gases, including their uncertainties. In parallel, simulations of the target time series have been 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, and to explain the observed trends. The final results of the project will be presented, and ways to proceed will be discussed. [less ▲]

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See detailInversion et caractérisation de profils de constituants atmosphériques fluorés à partir de spectres infrarouges enregistrés au Jungfraujoch
Duchatelet, Pierre ULg

Master of advanced studies dissertation (2005)

La composition de l’atmosphère terrestre évolue, suite à l’accumulation d’un nombre croissant de constituants gazeux chimiquement et radiativement actifs, émis au sol par les activités humaines. Ces ... [more ▼]

La composition de l’atmosphère terrestre évolue, suite à l’accumulation d’un nombre croissant de constituants gazeux chimiquement et radiativement actifs, émis au sol par les activités humaines. Ces émissions croissantes influencent l’ozone atmosphérique, l’équilibre radiatif de la Terre (et dès lors son climat) et modifient le niveau d’oxydation de son atmosphère. Une meilleure connaissance de la composition atmosphérique et une compréhension approfondie des processus physiques et chimiques qui prévalent dans la troposphère et la stratosphère sont essentielles pour établir l’état actuel de notre environnement, pour en comprendre les changements récents et en cours, et pour en prédire l’évolution future. Elle est également indispensable pour fournir une solide base scientifique aux mesures régulatoires de pratiques industrielles et humaines, liées aux Protocoles de Montréal et de Kyoto. L’acquisition de cette connaissance nécessite des mesures troposphériques et stratosphériques, basées notamment sur des observations récurrentes à partir du sol. A moyenne latitude, ces observations sont réalisées par l’Université de Liège à la Station Scientifique Internationale du Jungfraujoch (ISSJ, 46.55°N, 8.98°E, 3580m d’altitude, Alpes suisses) à l’aide de deux spectromètres par transformée de Fourier à haute résolution opérant dans l’infrarouge. Les observations FTIR systématiques de l’atmosphère terrestre au Jungfraujoch ont débuté dès 1985. Il a en effet été démontré que la continuation ininterrompue de mesures à long terme joue un rôle primordial dans la recherche sur les changements atmosphériques globaux focalisés sur la chimie et la dynamique de l’atmosphère et le climat terrestre. Les données ainsi recueillies au Jungfraujoch par l’Université de Liège se sont déjà révélées extrêmement utiles pour l’étude de la variabilité et de l’évolution à long terme d’un grand nombre d’espèces. La base de données constituée au fil des années d’observation s’exprime pour chaque constituant en termes de colonne verticale totale, déduite à partir de l’algorithme SFIT-1. Cependant, depuis le début des années 2000, un nouveau code, SFIT-2, permet, en plus d’obtenir la colonne verticale de l’espèce cible, de déduire son profil de distribution verticale. La détermination de colonnes partielles a également été rendue possible. De cet essor, s’en est accompagné le développement de bon nombre d’outils de caractérisation de profils FTIR et de formalismes de comparaison entre distributions verticales issues d’instruments différents. L’analyse du contenu en information et l’analyse d’erreur des profils inversés constituent les principaux outils permettant de caractériser les données FTIR. L’un des objectifs premiers du présent travail est par conséquent de fournir un aperçu des possibilités liées à l’algorithme d’inversion SFIT-2 ainsi qu’à ses outils de caractérisation. Ces outils, décrits en détail dans ce travail, ont été appliqués à l’inversion et à la caractérisation des distributions verticales de deux gaz atmosphériques, HF et COF2 (Chapitre 4). Ces gaz ont été choisis car ils représentent les deux principaux réservoirs de fluor stratosphérique dont l’importance permet de quantifier indirectement l’impact de l’activité humaine sur l’érosion de la couche d’ozone. Les profils ainsi déduits ont également été comparés aux mesures réalisées par le satellite canadien ACE lors de ses passages au-dessus du Jungfraujoch. Auparavant, après un bref aperçu des propriétés physiques et chimiques de l’atmosphère, nous évoquons toute la problématique des phénomènes d’effet de serre et d’érosion de couche d’ozone, dans lesquels les constituants fluorés sont directement ou indirectement impliqués (Chapitre 1). Nous décrivons ensuite les réactions qui régissent la chimie du fluor atmosphérique pour montrer comment les réservoirs prennent naissance à partir des gaz sources émis en surface. L’importance de ces réservoirs ainsi que leur évolution sont également largement abordées (Chapitre 2). Après avoir évoqué les notions fondamentales liées à la spectrométrie par transformée de Fourier, nous décrivons les instruments et les bases de données observationnelles qui leur sont associées (Chapitre 3) et qui nous ont aidés à produire les résultats géophysiques présentés dans la dernière partie de ce travail. [less ▲]

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See detailComparisons between ACE-FTS and ground-based measurements of stratospheric HCl and ClONO2 loadings at northern latitudes
Mahieu, Emmanuel ULg; Zander, Rodolphe ULg; Duchatelet, Pierre ULg et al

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 ... [more ▼]

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. [less ▲]

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See detailEvolution of a dozen non-CO2 greenhouse gases above central Europe since the mid-1980s
Zander, Rodolphe ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

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 ... [more ▼]

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. [less ▲]

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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 ULg; Dzhola, A. V. et al

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 ... [more ▼]

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. [less ▲]

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See detailRecent Evolution of atmospheric OCS above the Jungfraujoch station : implications for the stratospheric aerosol layer.
Mahieu, Emmanuel ULg; Zander, Rodolphe ULg; Demoulin, Philippe ULg et al

in Proceedings of the Atmospheric Spectroscopy Applications. (2005)

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