Mapping Snow Depth in the Alps

The Swiss Federal Institute for Snow and Avalanche Research SLF publishes snow depth maps of Switzerland. These maps provide valuable input for avalanche warning, hydrological snowmelt runoff modelling, climatology, winter tourism and popular geovisualizations e.g. dynamic overlays for Google Earth. The snow depth maps are derived from snow station measurements using a spatial interpolation method based on the dependency of snow depth on altitude. On days with little cloud cover, an operational snow cover product obtained from the polarorbiting NOAA AVHRR satellite is included in the GIS analysis. Through this process, an additional set of virtual snowfree stations is gained to increase the density of the imeasurements. The resulting snow depth maps are calculated at a spatial resolution of 1x1 km. In this study we transfer and adapt this approach to the neighbouring region of South Tyrol (northern Italy). In a case study we demonstrate the merging technique and evaluate its accuracy based on cross-validation analysis. The error estimates indicate that the introduction of virtual snowfree stations results in an improved spatial snow depth interpolation. Limiting factors are associated with the number of cloud free satellite images and the sub-optimal illumination conditions during mid-winter in the rough alpine terrain. For the future, an alpine-wide snow depth map would be of great interest. Also, an adaptation and application to other mountain regions in the world could be of great relevance.