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See detailGround-based CO observations at the Jungfraujoch: Comparison between FTIR and NDIR measurements
Dils, Bart; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

in Geophysical Research Abstracts (2008), 10

Measurements of CO have been performed at the Swiss Alpine Jungfraujoch station (46.5º N, 8.0° E, 3580m a.s.l.) on a regular basis since the mid-1980’s, using Fourier Transform Infrared solar absorption ... [more ▼]

Measurements of CO have been performed at the Swiss Alpine Jungfraujoch station (46.5º N, 8.0° E, 3580m a.s.l.) on a regular basis since the mid-1980’s, using Fourier Transform Infrared solar absorption spectrometry (FTIR), and since 1996 using an in situ Nondispersive Infrared technique (NDIR). While the in situ measurements detect local CO concentrations at the site, the FTIR technique provides integrated measurements along the line-of-sight. Nevertheless, the pressure broadening of the spectral absorption lines recorded at high resolution enables retrieving information on the vertical distribution of CO, mainly in the troposphere, including its concentration near the surface. Considering the inherent capabilities of the two independent measurement techniques, substantial differences between both data sets for surface level CO could potentially arise. Here we present a comparison of both data sets for the 1997 -2004 time period. Both data sets have been analysed by using successive Kolmogorov-Zurbenko filters. It appears that the long-term trend over the given time period is significantly different for both datasets. Possible causes for this difference will be critically discussed. [less ▲]

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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 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 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 detailOn the line parameters for the X 1sigma+g (1–0) infrared quadrupolar transitions of 14N2
Goldman, Aaron; Tipping, R.H.; Ma, Q. et al

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

Re-examination of the 14N2 X 1sigma+g (1–0) line parameters in the HITRAN database showed that the vibration–rotation interaction effect on the line intensities has been neglected, and that the halfwidths ... [more ▼]

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

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See detailGeophysical validation of MIPAS-ENVISAT operational ozone data
Cortesi, U.; Lambert, J. C.; De Clercq, C. et al

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

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on-board the European ENVIronmental SATellite (ENVISAT) launched on 1 March 2002, is a middle infrared Fourier Transform spectrometer ... [more ▼]

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

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See detailValidation of MIPAS HNO3 operational data
Wang, D. Y.; Hopfner, Michael; Blom, C. E. et al

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

Nitric acid (HNO3) is one of the key products that are operationally retrieved by the European Space Agency (ESA) from the emission spectra measured by the Michelson Interferometer for Passive Atmospheric ... [more ▼]

Nitric acid (HNO3) is one of the key products that are operationally retrieved by the European Space Agency (ESA) from the emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. The product version 4.61/4.62 for the observation period between July 2002 and March 2004 is validated by comparisons with a number of independent observations from ground-based stations, aircraft/balloon campaigns, and satellites. Individual HNO3 profiles of the ESA MIPAS level-2 product show good agreement with those of MIPAS-B and MIPAS-STR (the balloon and aircraft version of MIPAS, respectively), and the balloon-borne infrared spectrometers MkIV and SPIRALE, mostly matching the reference data within the combined instrument error bars. In most cases differences between the correlative measurement pairs are less than 1 ppbv (5-10%) throughout the entire altitude range up to about 38 km (similar to 6 hPa), and below 0.5 ppbv (15-20% or more) above 30 km (similar to 17 hPa). However, differences up to 4 ppbv compared to MkIV have been found at high latitudes in December 2002 in the presence of polar stratospheric clouds. The degree of consistency is further largely affected by the temporal and spatial coincidence, and differences of 2 ppbv may be observed between 22 and 26 km (similar to 50 and 30 hPa) at high latitudes near the vortex boundary, due to large horizontal inhomogeneity of HNO3. Similar features are also observed in the mean differences of the MIPAS ESA HNO3 VMRs with respect to the ground-based FTIR measurements at five stations, aircraft-based SAFIRE-A and ASUR, and the balloon campaign IBEX. The mean relative differences between the MIPAS and FTIR HNO3 partial columns are within +/- 2%, comparable to the MIPAS systematic error of similar to 2%. For the vertical profiles, the biases between the MIPAS and FTIR data are generally below 10% in the altitudes of 10 to 30 km. The MIPAS and SAFIRE HNO3 data generally match within their total error bars for the mid and high latitude flights, despite the larger atmospheric inhomogeneities that characterize the measurement scenario at higher latitudes. The MIPAS and ASUR comparison reveals generally good agreements better than 10-13% at 20-34 km. The MIPAS and IBEX measurements agree reasonably well (mean relative differences within +/- 15%) between 17 and 32 km. Statistical comparisons of the MIPAS profiles correlated with those of Odin/SMR, ILAS-II, and ACE-FTS generally show good consistency. The mean differences averaged over individual latitude bands or all bands are within the combined instrument errors, and generally within 1, 0.5, and 0.3 ppbv between 10 and 40 km (similar to 260 and 4.5 hPa) for Odin/SMR, ILAS-II, and ACE-FTS, respectively. The standard deviations of the differences are between 1 to 2 ppbv. The standard deviations for the satellite comparisons and for almost all other comparisons are generally larger than the estimated measurement uncertainty. This is associated with the temporal and spatial coincidence error and the horizontal smoothing error which are not taken into account in our error budget. Both errors become large when the spatial variability of the target molecule is high. [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 detailAn empirical line-by-line model for the infrared solar transmittance spectrum from 700 to 5000 cm(-1)
Hase, F.; Demoulin, Philippe ULg; Sauval, A. J. et al

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

An empirical line-by-line model for the infrared solar transmittance spectrum is presented. The model can be incorporated into radiative transfer codes to allow fast calculation of all relevant emission ... [more ▼]

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