Monitoring Swiss alpine snow cover variations using digital NOAA-AVHRR data

Within a research project and the programme for a Hydrologic Atlas of Switzerland, charts of the extent and the variations of the snow cover in Switzerland for two hydrologically and meteorologically different years were derived from digital NOAA-AVHRR data. During the two years, 32 satellite scenes were classified using supervised classification techniques. For the generation of the snow cover charts, up to 12 categories (several sub-categories for vegetation, water, snow, and clouds) were used. The final results were thematic maps differentiating between snow covered and non-snow covered (aper) areas. The snow cover charts were geocoded to the Swiss reference system using a ground-control-point approach allowing the superimposition onto a digital elevation model (DEM) and a digital boundary map of Switzerland within a geographic information system (GIS). Based on this data set, the snow coverage and its variations as well as the snowline for the two years under investigation were determined for several river basins in Switzerland. Furthermore, snow cover depletion curves for the two ablation periods, separately for several elevation zones, were generated which were necessary for snowmelt runoff computations in the Rhine-Felsberg basin using the SRM Model.