An investigation of scattering mechanisms from snow covered ice

Through a combined study using scattering models and measurements from saline ice with and without snow cover, the authors found that the presence of snow cover can generate either a larger dielectric discontinuity at the snow-ice interface or a rougher interface condition than the case without snow cover. This happens because of the possibility of brine wicking up from the saline ice into the snow-ice interface. To further pin down the relative importance of these two mechanisms, they performed experiments on bare and saline and snow-covered saline ice at CRREL during the winter 1994-95. They made measurements over a wide range of microwave frequencies with HH and VV polarizations. They study these scattering effects using a 6´-diameter, 25 cm deep tank that can be rotated to facilitate collection of a large number of independent samples. Comparisons with model predictions are carried out to pin down the relative importance of these two mechanisms. Theoretical studies have shown that backscattering due to a larger vertical roughness parameter will cause a smaller return at normal incidence and a faster drop off with the incidence angle will occur if the horizontal roughness scale becomes larger. At large angles of incidence the vertically polarized return should be higher than the horizontally polarized return. On the other hand, if the main effect of brine wicking is to increase the discontinuity at the snow-ice-interface, then the angular drop off rate will nor change much over the small incidence angle region and horizontally polarized return may be close to the vertically polarized return at large angles of incidence. Thus, it is possible to investigate the relative importance of these mechanisms with an experiment designed to obtain a reliable backscattering angular trend and polarization dependence