The Cryosphere Discuss., 4, 865-900, 2010
www.the-cryosphere-discuss.net/4/865/2010/
doi:10.5194/tcd-4-865-2010
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under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal The Cryosphere (TC). Please refer to the corresponding final paper in TC.
Understanding snow-transport processes shaping the mountain snow-cover
R. Mott, M. Schirmer, M. Bavay, T. Grünewald, and M. Lehning
WSL Institute of Snow and Avalanche Research Davos, Davos, Switzerland

Abstract. Mountain snow-cover is normally heterogeneously distributed due to wind and precipitation interacting with the snow cover on various scales. The aim of this study was to investigate snow deposition and wind-induced snow transport processes on different scales and to analyze some major drift events caused by North-West storms during two consecutive accumulation periods. In particular, we distinguish between the individual processes that cause specific drifts using a physically based model approach. Very high resolution wind fields (5 m) were therefore computed with the atmospheric model Advanced Regional Prediction System (ARPS) and used as input for a model of snow surface processes (Alpine3D) to calculate saltation, suspension and preferential deposition of precipitation. Several flow features during North-West storms were identified with input from a high-density network of permanent and mobile weather stations and indirect estimations of wind directions from snow surface structures, such as snow dunes and sastrugis. We also used Terrestrial and Airborne Laser Scanning measurements to investigate snow deposition patterns and to validate the model. The model results suggest that the in-slope deposition patterns we found, particularly two huge cross-slope cornice-like drifts, developed only when the prevailing wind direction was northwesterly and were formed mainly due to snow redistribution processes (saltation-driven). In contrast, more homogeneous deposition patterns on a ridge scale were formed during the same periods mainly due to preferential deposition of precipitation. The numerical analysis showed that snow-transport processes were sensitive to the changing topography due to the smoothing effect of the snow cover.

Citation: Mott, R., Schirmer, M., Bavay, M., Grünewald, T., and Lehning, M.: Understanding snow-transport processes shaping the mountain snow-cover, The Cryosphere Discuss., 4, 865-900, doi:10.5194/tcd-4-865-2010, 2010.
 
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