136 research outputs found

    On the feasibility of retrieving 16O 18O 16O ozone from high resolution ground-based FTIR spectra

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    We present evidence of the 16O 18O 16O ozone isotope in the 5 micron region from FTIR solar occultation spectra obtained from the Jungfraujoch Solar Observatory (47°N, 8°E, 3580 m) in Switzerland at a spectral resolution of 0,0025 cm-1 (res. = 1/2L). These spectra clearly show numerous unblended lines of the 16O 18O 16O ozone isotope. Laboratory spectra in the 5 micron region of 16O 18O 16O have been measured and have yielded line positions of the nu1 + nu3 isotopic bands which can eventually lead to their retrieval from measured ground-based solar occultation spectra

    Chemical ozone loss in the Arctic winter 1991–1992

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    Chemical ozone loss in winter 1991–1992 is recalculated based on observations of the HALOE satellite instrument, Version 19, ER-2 aircraft measurements and balloon data. HALOE satellite observations are shown to be reliable in the lower stratosphere below 400 K, at altitudes where the measurements are most likely disturbed by the enhanced sulfate aerosol loading, as a result of the Mt.~Pinatubo eruption in June 1991. Significant chemical ozone loss (13–17 DU) is observed below 380 K from Kiruna balloon observations and HALOE satellite data between December 1991 and March 1992. For the two winters after the Mt. Pinatubo eruption, HALOE satellite observations show a stronger extent of chemical ozone loss towards lower altitudes compared to other Arctic winters between 1991 and 2003. In spite of already occurring deactivation of chlorine in March 1992, MIPAS-B and LPMA balloon observations indicate that chlorine was still activated at lower altitudes, consistent with observed chemical ozone loss occurring between February and March and April. Large chemical ozone loss of more than 70 DU in the Arctic winter 1991–1992 as calculated in earlier studies is corroborated here

    Towards IASI-New Generation (IASI-NG): impact of improved spectral resolution and radiometric noise on the retrieval of thermodynamic, chemistry and climate variables

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    Besides their strong contribution to weather forecast improvement through data assimilation, thermal infrared sounders onboard polar-orbiting platforms are now playing a key role for monitoring atmospheric composition changes. The Infrared Atmospheric Sounding Interferometer (IASI) instrument developed by the French space agency (CNES) and launched by Eumetsat onboard the Metop satellite series is providing essential inputs for weather forecasting and pollution/climate monitoring owing to its smart combination of large horizontal swath, good spectral resolution and high radiometric performance. EUMETSAT is currently preparing the next polar-orbiting program (EPS-SG) with the Metop-SG satellite series that should be launched around 2020. In this framework, CNES is studying the concept of a new instrument, the IASI-New Generation (IASI-NG), characterized by an improvement of both spectral and radiometric characteristics as compared to IASI, with three objectives: (i) continuity of the IASI/Metop series; (ii) improvement of vertical resolution; (iii) improvement of the accuracy and detection threshold for atmospheric and surface components. In this paper, we show that an improvement of spectral resolution and radiometric noise fulfill these objectives by leading to (i) a better vertical coverage in the lower part of the troposphere, thanks to the increase in spectral resolution; (ii) an increase in the accuracy of the retrieval of several thermodynamic, climate and chemistry variables, thanks to the improved signal-to-noise ratio as well as less interferences between the signatures of the absorbing species in the measured radiances. The detection limit of several atmospheric species is also improved. We conclude that IASI-NG has the potential for strongly benefiting the numerical weather prediction, chemistry and climate communities now connected through the European GMES/Copernicus initiative

    Validation and data characteristics of methane and nitrous oxide profiles observed by MIPAS and processed with Version 4.61 algorithm

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

    Advanced exploitation of ground-based Fourier transform infrared observations for tropospheric studies over Europe: achievements of the UFTIR project

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    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

    Les raies moléculaires de l'atmosphère solaire dans l'infrarouge (spectroscopie, transfert radiatif et modélisation physico-chimique du CO et de ses isotopomères)

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    Pour déterminer l'abondance O/H et les rapports isotopiques de C et de O dans le soleil, nous avons développé un modèle chimique photosphérique, un modèle de transfert radiatif qui détermine le spectre émergent et un programme d'inversion qui restitue les abondances de CO et de ses isotopomères à partir de spectres solaires infrarouge. Dans le modèle thermochimique, nous avons sélectionné les espèces à prendre en compte pour modéliser l'abondance du CO et le fond continu dans l'infrarouge. Nous avons construit un modèle à trois composantes à partir de champs hydrodynamiques 3D. Nous avons modélisé les coefficients d'élargissement collisionnels CO-H jusqu'à J=150 et à haute température à partir des coefficients CO-He et CO-H2 à plus basse température pour de plus faibles J. L'inversion des largeurs équivalentes des raies de CO nous a permis d'obtenir un rapport O/H=575+/-30, des rapports isotopiques 12C/13C=85+/- 10, 16O/18O=485+/-75 et 16O/17O=1700.+/-700.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

    Développement et caractérisation d'un spectromètre diode laser pour la mesure en continu et in situ de la composition atmosphérique en 12CO2 et en 13CO2

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    Ce manuscrit présente l'instrument SIMCO (Spectrometer for Isotopic Measurements of CO2) dont le développement s'inscrit dans le contexte scientifique général de l'étude de l'influence des émissions anthropogéniques de gaz à effet de serre sur le climat. La mesure de la concentration totale de CO2 et de la composition isotopique atmosphérique +-13CO2 permet de mieux faire la part entre les processus biogéochimiques et les processus d'origine anthropogénique. Cependant, la très faible amplitude de variation de la composition isotopique dans l'atmosphère implique d'obtenir une exactitude sur la mesure (en unités de +-13C) meilleure que 0,2 et une excellente stabilité de l'instrument. La problématique de l'augmentation de la concentration de CO2 dans l'atmosphère est exposée en introduction par un bilan des connaissances actuelles que l'on a du cycle du carbone. Puis l'état de l'art de la mesure de gaz à l'état de trace par spectroscopie d'absorption est décrit afin de justifier la configuration expérimentale choisie. Enfin, après avoir rappelé les fondements de la spectroscopie des isotopes du CO2, le montage expérimental retenu et développé, ses performances (et notamment les résultats de deux campagnes de mesures permettant de confronter les mesures de l'instrument SIMCO à celles d'un chromatographe en phase gazeuse et d'un spectromètre de masse) ainsi que les futures améliorations de l'instrument SIMCO sont présentés.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF
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