Review of signature studies for microwave remote sensing of snowpacks

Abstract A long-term program of microwave-signature studies at the alpine test site, Weissfluhjoch (2550m altitude), was completed in 1987. Besides passive microwave data at frequencies between 5 and 100 GHz backscatter data at 10 GHz were collected together with dielectric and structural properties as well as classical snow data. The same instrumentation was used from icebreakers to measure snow-covered sea ice. Complementary snow signatures were recently obtained by a new multichannel (1–12 GHz) radiometer-scatterometer at lower-altitude test sites for taking into account possible spatial variability of snow properties, and for extending the spectral coverage to lower frequencies. The results include algorithms for classifying snow types, for mapping snow, for determining the liquid water content of the snow surface, for monitoring melt and refreeze cycles, for estimating energy loss and water equivalent, respectively. We conclude by an updated definition of an optimum snow sensor system.