Rumble project - scattering index models

In this note we describe some models for the backscattering strength of a rough seafloor. The models range from the simple Lambert’s rule to perturbation models that include the effect of roughness and volumeinhomogeneities. For grazing angles in the range say 5-400, the dependence of backscattering strength on grazing angle can in many cases be described by Lambert’s rule. To obtain good correspondence with observations outside this range of angles, it may be necessary to include modifications to the Lambert’s rule: At lower grazing angles to include the effect of scattering by volume inhomogeneities, and near normal incidence to include the coherent component. If we want to relate the backscattering strength to physical parameters of the seafloor, it is necessary to use physical models. Two such models are included: A first order perturbation models for roughness scattering, and a first order perturbation model for volume scattering. A collection of information about roughness and topography of seafloors is also included.