P5.22 Development and Evaluation of the Amsu-based Snow Water Equivalent Retrieval Algorithm

The estimation of snow water equivalent (SWE) from passive microwave sensors remains a formidable challenge primarily due to the non-unique nature of the microwave scattering signatures over snow cover surfaces. Ideally, there is a straightforward relationship between the volume of snow crystals present in the snow pack, and hence, SWE or snow depth, and the degree of microwave scattering by ice grains, measured by the drop in the brightness temperature (TB) observed by the satellite at a specific microwave window frequency. The degree of scattering can also be measured by computing a Scattering Index (SI) as the positive difference in TB measured at two microwave frequencies, TBν1 – TBν2 where v indicates frequency and ν2 > ν1. This spectral scattering signature, e.g., the decrease in TB with increasing frequency is unique to snow-cover surfaces, and as such has been used successfully for the identification of global snow cover (Grody, 1991). Similar to snow cover identification, this scattering index approach is also used for the retrievals of SWE. (Chang et al., 1987; Goodison and Walker, 1994).