Simulation of wind-induced snow transport and sublimation in alpine terrain using a fully coupled snowpack/atmosphere model

In alpine regions, wind-induced snow transport strongly influences the spatio-temporal evolution of the snow cover throughout the winter season. To gain understanding on the complex processes that drive the redistribution of snow, a new numerical model is developed. It directly cou- ples the detailed snowpack model Crocus with the atmo- spheric model Meso-NH. Meso-NH/Crocus simulates snow transport in saltation and in turbulent suspension and in- cludes the sublimation of suspended snow particles. The cou- pled model is evaluated against data collected around the ex- perimental site of Col du Lac Blanc (2720 m a.s.l., French Alps). First, 1-D simulations show that a detailed represen- tation of the first metres of the atmosphere is required to reproduce strong gradients of blowing snow concentration and compute mass exchange between the snowpack and the atmosphere. Secondly, 3-D simulations of a blowing snow event without concurrent snowfall have been carried out. Re- sults show that the model captures the main structures of at- mospheric flow in alpine terrain. However, at 50 m grid spac- ing, the model reproduces only the patterns of snow erosion and deposition at the ridge scale and misses smaller scale patterns observed by terrestrial laser scanning. When acti- vated, the sublimation of suspended snow particles causes a reduction of deposited snow mass of 5.3 % over the calcu- lation domain. Total sublimation (surface + blowing snow) is three times higher than surface sublimation in a simulation neglecting blowing snow sublimation.