Probability density function of ocean surface slopes from radar observations

Airborne radar observations of the sea surface at C-Band and small incidence angles are used to investigate some properties of the surface slope probability density function (pdf). The method is based on the analysis of the variation of the radar cross-section with incidence angle, assuming that the backscatter can be described by the Geometrical Optics theory. First, we show that roughness properties with scales larger than 12 cm can be analyzed in our configuration (C-Band, incidence 7 to 16 degrees). The radar data are then analyzed in terms of filtered mean square slope under the assumption of a Gaussian slope pdf. Dependence with wind speed of the upwind and total mss are analyzed and compared to various published studies. Finally an analysis of the radar data under a non-Gaussian assumption for the slope pdf is proposed, by applying the compound model suggested by Ill.