Inhomogeneous precipitation distribution and snow transport in steep terrain

The inhomogeneous snow distribution found in alpine terrain is the result of wind and precipitation interacting with the (snow) surface over topography. We introduce and explain preferential deposition of precipitation as the deposition process without erosion of previously deposited snow and thus in absence of saltation. A numerical model is developed, describing the relevant processes of saltation, suspension, and preferential deposition. The model uses high-resolution wind fields calculated with a meteorological model, ARPS. The model is used to simulate a 120 h snow storm period over a steep alpine ridge, for which snow distribution measurements are available. The comparison to measurements shows that the model captures the larger-scale snow distribution patterns and predicts the total additional lee slope loading well. However, the spatial resolution of 25 m is still insufficient to capture the smaller-scale deposition features observed. The model suggests that the snow distribution on the ridge scale is primarily caused by preferential deposition and that this result is not sensitive to model parameters such as turbulent diffusivity, drift threshold, or concentration in the saltation layer.