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PhD Defense


Title : A climatology of dust aerosol properties retrieved from hyperpsectral infrared observations. Application to AIRS and IASI sounders.

Date and time : The 06-12-2010 at 09h00

Type : thèse

Université qui délivre le diplôme :

Location : Ecole Polytechnique, Amphithéâtre Becquerel, Palaiseau (91)
Members of jury :

M. Olivier BOUCHER (MetOffice, UK) : Rapporteur

M. Xavier BRIOTTET (ONERA) : Rapporteur

M. Alain CHEDIN (LMD, CNRS) : Directeur de thèse

Mme Hélène CHEPFER (LMD, UPMC) : Examinatrice

Mme Laurence PICON (LMD, UPMC) : Co-directrice

Mme Clémence PIERANGELO (CNES) : Examinatrice

M. Didier TANRE (LOA, CNRS) : Examinateur

Summary :

Aerosols, coming from either natural or anthropogenic sources, play an important role in the Earth’s climate. In suspension in the atmosphere, these particles interact directly with solar and terrestrial radiation, and also with climate processes through the other components of the atmosphere. The impact of aerosols on the total radiative balance of the Earth is still difficult to quantify, in part due to the difficulty of measuring precisely their microphysical and optical properties. Their highly variable spatial and temporal distribution makes their study even more complex.

Multiple space observations, at different wavelengths and using different measurement techniques, offer a means to understand the role of aerosols. Among passive remote sensing methods, the use of infrared sounding is still lagging behind visible techniques. Yet, besides allowing the closure of the total radiative balance, infrared sounding also allows acquiring observations during both night and day, over ocean and over land. Access to the mean altitude of aerosols is a key point of infrared remote sensing.

This PhD thesis deals with an inversion method developed for hyperspectral infrared sounders such as AIRS/Aqua and IASI/Metop-A. Based on this method, a 8-year (2003–2010) climatology of dust aerosol properties (optical depth at 10 µm and mean altitude) has been obtained. These results have been validated using the temporal and spatial synergy brought by other instruments onboard the satellite constellation “A-Train” (MODIS/Aqua, CALIOP/CALIPSO, PARASOL). The spatial distribution and natural cycles of desert dust in the tropics are described. Thanks to the very high spectral resolution brought by IASI, the method has been extended to the retrieval of the effective radius of the dust coarse mode, which allows completing the study of dust aerosol evolution through atmospheric transport.

Keywords : microphysical and optical properties, dust aerosols, infrared remote sensing, AIRS, IASI, A-Train, inversion method.

Diploma delivered by :
Université Pierre et Marie Curie

Contact :
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