Statistical approach to derive snow lines in an alpine basin from high resolution snow cover monitoring

The rugged relief of the Alps makes it difficult to determine the altitude of the snow line because the seasonal snow cover consists of snow fields, snow patches and snow-free areas in an altitude range of several hundred meters. A statistical approach based on high resolution periodical snow cover mapping is adopted in order to derive the position of a statistical snow line within a belt of approximately 50% snow coverage. The gradual rise of snow line during the snowmelt season is evaluated in the basin of the Rhône at Sion by mapping the snow cover in elevation zones with 100 m and 20 m altitude steps. The position of the statistical snow line is interpolated within the zone nearest to 50% snow coverage separately for partial areas of the basin and for glaciers.