Snow cover monitoring in alpine regions with COSMO-SkyMed images by using a multitemporal approach and depolarization ratio

The multi-temporal technique for the detection of wet snow, based on the different response of snow and no-snow area was applied to COSMO-SkyMed (CSK) images acquired over South Tyrol (Northern Italy) during the first year of activity in the project “SNOX - snow cover and glacier monitoring in alpine areas with COSMO-SkyMed X-band data” funded by the Italian Space Agency. A standard threshold value of -3 dB and a less restrictive threshold of -2.3 dB are compared for an improved distinction of the snow and no-snow distributions. The application of these two different thresholds determines a variation of snow cover area (SCA) between 2% and 8%. Furthermore, it has been proved that the choice of the reference image for the no-snow areas is critical and can determine a variability in the resulting SCA up to 10%. The depolarization factor, σ⁰_VH/σ⁰_VV, is also exploited to evaluate its contribution to the identification of snow covered areas. Preliminary results indicate that the contribution of the depolarization factor to the SCA detection is very limited.