Polarimetric and interferometric methods to determine snow depth, SWE, and the depth of fresh snow

Abstract

Microwaves interact with snow on a wide variety of effects. The specific effect of interaction depends mainly on liquid water content which determines the penetration depth. The penetration depth changes by orders of magnitude at the transition from dry snow to wet snow. Further affects appear due to roughness of the boundary layers soil-snow and snow-air and discontinuities in the snow pack. Even the microstructural anisotropy of snow affects the interaction with microwaves. Therefore, complementary methods have to be applied to access the medium snow in all it's facets. Here, I will demonstrate different polarimetric and interferometric methods, which show a sensitivity to certain properties of snow. Surface-sensitive methods apply only for wet snow, due to the very limited penetration depth, especially at high frequencies. I will demonstrate, that the height difference of two single-pass interferograms taken by TanDEM-X is equivalent to the height of accumulated snow within one winter season. In contrast to wet snow, I will demonstrate, that it is possible to derive the total snow water equivalent (SWE) of dry snow from a time series of differential interferograms. Going beyond height or SWE sensitive methods, I will demonstrate a polarimetric method, which is sensitive to the microstructure of snow. A simple model will be presented, which shows that the phase delay of the HH vs. the VV polarization is sensitive to the amount of fresh snow and to the temperature-gradient driven metamorphism of snow.