Geometrical optics prediction of surface scattering statistics

A composite-roughness formulation of the geometrical optics approximation is applied to study the statistics of near-nadir electromagnetic scattering from the sea surface. For scattering from Gaussian random surfaces, the scattering cross section is dependent only on the probability density of surface slopes. The statistical distribution of the scattered intensity depends on both the slope probability density function and <|Ω|> $the mean absolute value of the surface curvature. The curvature is of interest because it provides a measure of capillary wave spectra. Numerical results are obtained for scattering from isotropic surfaces for a fixed number N of specular scatterers and for N Poisson distributed. Obtaining viable estimates of <|Ω|>, and hence of capillary wave spectra, from backscatter data at microwave frequencies may not be practical. Optical measurements for which individual point scatterers can be identified may, however, yield estimates of the surface curvature.