Modulation of L-band signals by the sea surface roughness

Abstract

In the context of the ESA SMOS and Aquarius/SAC-D missions, sea surface thermal emission in L-band is measured from space since almost 3 and 1 years respectively. Using a new instrumental concept for the first one, a Microwave Imaging Radiometer using two dimensional aperture synthesis, sea surface brightness temperatures can be extracted under a large range of incidence and azimuthal angles, and different spatial resolutions. Although using a more classical real aperture radiometer, Aquarius derives its originality from measuring quasi simultaneously active and passive signals for three different incidence and azimuthal angles. A lot of works have been done the last ten years to develop physically based scattering models in order to accurately predict the sea surface roughness impact on brightness temperatures. Recent results have shown that non negligible discrepancies exist between these models and this new data set of L-band measurements. This presentation will provide a review of the last empirical adjustments of radar normalized cross sections and sea surface brightness temperatures modulations by different sea surface roughness characteristics. A discussion regarding possible improvements in electromagnetic scattering modeling and inherent sea surface spectral description will be proposed