Sublimation of drifting snow in an Alpine catchment

In mountainous regions, drifting snow has a large impact on hydrology, snow distribution, snowcover stratigraphy and avalanche risk. A weakness in most of the existing drifting snow models is the representation of drifting snow sublimation. No field measurements exist and model estimates vary from 4 to 70 % of winter snowfall for the Alpine region. We are extending an existing snow transport model, Alpine3D, with a module for drifting snow sublimation. In previous approaches, temperature and humidity feedbacks or advection were frequently neglected. We introduce a drifting snow sublimation model that includes all these effects. The model could partially be validated in a wind tunnel.

We will consider a test case in a complex Alpine catchment with steep slopes. Here we will estimate the importance of sublimation itself and of the different feedbacks, though the strong dependence on the initial conditions makes a generalization impossible. Preliminary results show a decrease of deposited snow up to 40 % in a lee slope. Averaged over the research area however, the snow deposition is reduced by only 2%. Furthermore, the difference in deposition when including the temperature feedback is just as large as the difference in deposition caused by the sublimation, showing that this feedback can't be neglected. The influence of the humidity feedback appears to be even larger. The inclusion of these significant feedbacks will therefore allow us to give a more accurate estimate of drifting snow sublimation in the Alpine region.