Snow surface slope and differential snow metamorphosis rate impact on SAR sea ice images interpretation

While dry snow is almost transparent to frequencies used by SAR satellites, a water content over 8% reduces penetration to a level that causes the backscattered component to come mostly from surface scattering. Snow metamorphosis is initiated by incoming solar radiation increase and depends on a number of parameters controlling heat exchanges within the snow layer. With variable surface slopes, net solar radiation influx and absorption may differ significantly within a target and impact its dielectric properties. Beside, surface slope orientation influences air flows over each and every snow-air interface and therefore the evaporation rate which in turn controls the latent heat consumed in the process. Vertical profiles of the water content are computed for a range of surface slope orientation, solar radiation influx and evaporation induced latent heat rates. Surface water content variability induced by the radiation diurnal cycle is simulated and the scattering impact inferred. While snow metamorphosis differential rates were confirmed from field observations, the main impact on SAR sea ice images interpretation was mainly related to liquid water content at the snow-air interface and the increased surface scattering incidence angle dependence from electromagnetically smooth surfaces.