HIGH-FREQUENCY FORWARD SCATTERING IN A REFRACTING OCEAN

The Kirchhoff approximation for scattering from random rough surfaces is extended to treat the general case of forward boundary scattering in a refractive underwater sound channel where multiple interactions with the surface may occur. Various approximations are obtained for the scattered intensity and the spatial covariance in the high-frequency limit. Numerical examples are presented to demonstrate the strong predicted dependence of both the reflectivity and the spatial covariance on refraction. When acoustic energy is strongly refracted toward the scattering surface, all of these approximations fail to provide meaningful predictions of the scattered intensity.