Snow Classification Algorithm for Envisat Asar

Capabilities and methods for snow mapping in mountainous areas using the Advanced Synthetic Aperture Radar (ASAR) on board of ENVISAT were investigated. For algorithm development the backscattering signatures of snow covered and snow free surfaces in Alpine valleys and on mountain slopes were studied with ASAR data of different look angles and polarizations in comparison with field measurements of snow properties and meteorological data. The algorithm for automatic generation of snow maps during the melting period with ASAR applies multi-temporal change detection, the same principle as the method developed for ERS SAR. Impacts of various look angles (swathes), polarisations and image modes of ASAR for snow classification have been studied. The investigations demonstrate the suitability of ASAR Image Mode, Alternating Polarisation Mode and Wide Swath Mode for snow mapping in mountain areas, and the preference for steep incidence angle modes (IS6 and IS7) to minimize the loss of information due to layover and foreshortening. Time series of ASAR derived snow maps were produced for Alpine watersheds, confirming the high potential of this product for runoff modelling and forecasting.