A Backscatter Modeling for River Ice: Analysis and Numerical Results

A microwave backscatter model was developed to help provide an understanding of the interaction of a radar signal with the different ice types formed on natural freshwater bodies. This model was based on the radiative transfer theory, which is solved by the doubling matrix method. This numerical method provides an explanation for scattering effects due to volume, boundaries, boundary-volume interactions and interactions between layers. Three ice types were analyzed: columnar ice, frazil ice, and snow ice. Simulations with the model proved that the radar response from river ice cover depends on both ice-cover boundaries. The shape and distribution of air inclusions within the different ice types seem to have a significant impact on their contributions to the total response. The presence of tubular air inclusions within columnar ice causes an increase in the total response as a result of a double-bounce scattering. Small spherical and closed air inclusions within snow ice and frazil ice generate significant backscattering at high frequencies due to volume and surface-volume scattering. A further increase in the ice-cover thickness with air inclusions also causes increased scattering. Superposing two or more of these ice types causes considerable multiple scattering between layers. Finally, radar ice measurements collected over the Athabasca River were employed to further validate the model, and satisfactory results were obtained.