Abstract : The main objective of this thesis is to study the potential and the feasibility of atmospheric temperature and humidity profile retrievals over land using microwave sounding measurements and especially AMSU-A and-B ones.
Indeed, microwave measurements are assimilated over oceans in many meteorological centres but remain insufficiently exploited over land. The land emissivity is high (almost close to 1.0) and is highly variable with surface characteristics. Consequently, it is difficult to separate the relative contributions of the surface and the atmosphere to the measured radiances.
An important part of this work has been dedicated to the land emissivity estimation at AMSU frequencies (23-150 GHz) and scanning conditions (from -58 to +58 with respect to nadir). The land emissivity calculations have been conducted over the globe and using cloud free data from year 2000.
The land AMSU emissivities have been evaluated by examining their angular and spectral dependences and by comparison to SSM/I emissivities.
Theses analyses permit the development of a microwave land emissivity parameterization for frequencies ranging from 23 to 150 GHz and scanning angles up to 58.
Thereafter and with a good knowledge of the surface (emissivity and skin temperature), the feasibility of the AMSU temperature and humidity profiles has been studied by conducting an information content analysis. This study shows that AMSU measurements when combined with a reliable surface emissivity and skin temperature could produce valuable estimations of the atmospheric temperature and humidity profiles especially at atmospheric low levels.