The snow wetness and the onset of snow melting are two closely related variables that are important for the understanding of the hydrological regime of snow-covered mountain areas. The variables are indicators for the start of the growing season for the vegetation above the tree line, as well as being important for the management of the drainage system, in particular flood prediction and production of hydro-electrical power. This product is requested from the Norwegian users NVE and Statkraft.

 

 

It can be assumed that the snow starts melting when the snow has become wet or has been wet or moist for some time. The grain size of the snow will increase gradually, but the change will depend very much of the temperature and content of free water within the snow package. The snow wetness can thus be estimated indirectly from the combination of grain size development and snow surface temperature.

 

The approach estimates the snow surface wetness by combining estimates of the snow surface temperature and the snow grain size. Both of these can be retrieved from MODIS images. The main assumption is that when the surface temperature reaches the melting point and the grain size continues to increase, the snow has become wet.

 

 

Geoland project web site.