Frédéric Frappart (LEGOS-OMP, France); Denis Blumstein (CNES, France); Florence Birol (LEGOS-OMP, France); Rosemary Morrow (LEGOS-OMP, France); Frenando Niño (LEGOS-OMP, France)

If radar altimetry, initially designed for studying ocean surface topography, is mostly used for its capacity to determine surface height, the backscattering coefficients provide information on the surface properties. We propose here to analyze the spatio-temporal variations of radar backscattering coefficients over global ocean in the different frequency bands used in radar altimetry during the last 20 years. We present first global maps of along-track average backscattering coefficients and associated standard deviation at S, C, Ku and Ka bands using data from Jason-2, ERS-2, ENVISAT and SARAL on their nominal orbit over ocean. Then, we relate the resulting maps to the roughness of the surface and its temporal evolution in terms of seasonal cycle and interannual variability. We will focus on some regions as the Mediterranean Sea to discuss in details our results.