Apport de la double polarisation pour l'étude expérimentale et théorique de la section efficace radar de la surface océanique

Abstract : This thesis deals with the analysis of radar measurements (C band) in VV and HH polarisations to
improve the understanding of the interactions between the sea surface and the electromagnetic incident
wave in order to study the sea surface. First, we propose an empirical model which reproduces the
ratio of the radar cross-section as a function of incidence angle and wind direction. We show that
such a model can be used for wind field retrieval from SAR images. Then, we propose a comparison
between different kind of electromagnetic models and data. This study shows that a common part of
the radar signal in each polarisation must be modelled to fully reproduce the interactions between
electromagnetic waves and the sea surface. This common part can be attributed to the breaking waves
effects and plays a key role in the up/down-wind asymmetry of the signal. Finally, we investigate the
azimuth description of the radar signal, analysing possible effects of several surface processes. We
show that waves-waves non-linear interactions have a significant role on the wave spectrum azimuth
behaviour.