Modeling interpretation of active and passive measurements from sea ice

A combined surface-volume scattering model based on the radiative transfer formulation for an inhomogeneous layer above an inhomogeneous half space is developed using a dense medium phase function. This phase function gives the scattering properties of coherent scattering from a group of randomly positioned scatterers within a unit volume. For a bare saline ice or a snow-covered saline ice at C- and X-bands, backscattering at small angles of incidence is dominated by the air-ice or snow-ice interface. At large angles of incidence, volume scattering by ice, or snow and ice, is noticeable especially at higher frequencies. When the model is applied to passive measurements emission is found to be dominated by ice in the low frequency region. The presence of a snow cover enhances emission in the low frequency region and gradually turns into a darkening-effect when frequency exceeds 35 GHz. At 94 and 140 GHz emission is dominated by snow. As frequency increases, the effect of group scattering lowers the rate of increase in albedo and permits a larger difference between like and cross polarized backscattering in active sensing and slows down the rate of decrease in emissivity in passive sensing.