Non‐Gaussian effects in the two‐scale model for rough surface scattering

The popular two‐scale scattering model is applied to random surfaces whose probability density function of the slopes is described by the Gram‐Charlier type series. The particular form of the roughness spectrum pertains to the sea wave structure. Its angular factor is modified as to agree with the experimental data related to both the upwind and the crosswind rms slopes. A simple empirical factor, suggested earlier, is included in the spectrum to account for the modulation of the small ripples by the large waves. The results related to the azimuthal dependence of the backscattering cross section are shown to agree reasonably well with the airborne radar data acquired at Ku and X band in a circle flight pattern. It is also shown that the experimentally observed effects of upwind‐downwind asymmetry and the shift of the minimum of the backscattered power off the crosswind direction are related to the non‐Gaussian corrections. In addition, the particular coefficients in the slopes distribution responsible for the above two effects are singled out.