Complémentarité et représentativité des observations atmosphériques effectuées par instrumentation active et passive sur les nouvelles plates-formes spatiales

Abstract : One of the important objectives of the current climate research programs is the understanding of the impacts of clouds and aerosols on the global radiation budget. Indeed, clouds and aerosols have a significant influence on the Earth?s radiative balance and induce various climatic feedbacks that are still not enough known. The spatial heterogeneity of cloud structures and their microphysical properties significantly contribute to the modulation of the earth energy budget. Moreover, the surface longwave flux distribution is very sensitive to both the geometrical structures and altitudes of clouds. A first objective to improve existing climatic models is then to have a knowledge about the tri-dimensional distribution of cloud layers. Futhermore, spaceborne backscatter lidar systems allow new insights on the vertical distribution of aerosols. Second objective of this study is to improve the retrieval of aerosols properties over land, where retrievals from passive sensors are known to be more difficult due to surface contribution. To fullfile the first objective, I have applied and adapted an algorithm to assess the probability density function (PDF) of cloud layer top heights from GLAS (Geoscience Laser Altimeter System, NASA) and LITE Lidar (In-space Technology Experiment, NASA, 1994) profiles. The methodology is first explained and results based on all the GLAS and LITE data are presented and discussed. This method is validated by a sensibility study. Then, the synergy between active and passive measurements can lead to significant improvement of the lidar inversion. To answer the second objective, we present in the following of this work the potential of using the coupling between a spaceborne lidar (LITE) and a geostationary satellite (Meteosat-5) to retrieve the aerosol optical properties over both ocean and continent, with a focus on African dust. Therefore, a retrieval algorithm has been implemented. Results and validation of the method are presented. The error on the dust radiative impact has been assessed for this synergy, and by using the simultaneous data sets derived from other space-borne passive and active instruments.
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Sébastien Berthier. Complémentarité et représentativité des observations atmosphériques effectuées par instrumentation active et passive sur les nouvelles plates-formes spatiales. Autre. Université de Versailles-Saint Quentin en Yvelines, 2007. Français. ⟨tel-00327231⟩

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