Radar backscatter from a dense discrete random medium

Abstract

A dense medium phase matrix developed based on the concept of random lattice perturbation is employed in the radiative transfer theory to calculate the coand cross-polarized backscatter from a layer of randomly distributed spherical scatterers. The position randomness properties are characterized by the variance and correlation function of scatterer positions within the medium. The dense medium phase matrix differs from the conventional one in two major aspects, i.e., there is an amplitude and a phase correction. These corrections account for the effects of close spacing and position correlation between scatterers in a dense discrete random medium. This study shows that phase coherency and close-spacing amplitude modifications are two separate corrections necessary for an electrically dense medium. Results indicate that there is a need to distinguish between spatially and electrically dense medium. The phase correction is found to have a greater impact on cross-polarized than like-polarized backscatter coefficients; the converse is true of the amplitude correction. Backscattering calculations from the theory are compared with measurements from controlled microwave experiments on random media consisting of closely packed spheres, and from field measurements of dry snowpack. Predictions from such a theory agree well with the measured data.