Mapping Snow Cover in Alpine Areas with Envisat/sar Images

RESUME It has been established that optical and near-infrared sensors can monitor the seasonal variations of snow cover in alpine areas in cloud free conditions. However, only microwave sensors are able to acquire data independently of day light and in adverse weather conditions. The effects of dry snow on currently available C-band SAR data are rather small and difficult to detect. On the contrary, several experiments have documented their ability in mapping the extent of wet snow. In 2002-2004 a series of ERS SAR and ENVISAT ASAR images were collected on the Italian Alps to further evaluate the potential of C-band SAR data in remote sensing of snow and, in particular, in detecting temporal evolution of snow cover. A sequence of SAR images was analysed by comparing the backscattering of specific sub-areas of interest with insitu snow and meteo data, and through simulations performed with a model based on the Strong Fluctuation Theory. A multi-temporal analysis of C-band SAR images combined with results of model simulations and some “a priori” information was used to monitor the extent of snow cover.