Merging a terrain-based parameter with blowing snow fluxes for assessing snow redistribution in alpine terrain

Wind and the associated snow transport are dominating factors determining the snow distribution and accumulation in alpine areas. These factors result in a high spatial variability of snow heights that is difficult to quantify. In this study, we propose an efficient method for estimations of changes in snow heights during blowing snow events. We merge a terrain-based parameter Sx, which characterizes the degree of shelter or exposure of a point provided by the upwind terrain, with estimations of quantity of snow transported by the wind. This estimation is provided by snow particle counters (SPC) that estimate the snow flux, the mass of drifting snow particles per time and area. A modified terrain-based parameter Sx(m) is then used to distribute snow over the terrain. The results are compared with measured changes in snow heights resulting from blowing snow events, obtained with terrestrial laser scanning (TLS). Data and results are from the Col du Lac Blanc research site in the French Alps. We use a high raster resolution of 1 m, which is required when assessing the snow-redistribution situation in highly structured terrain or in the starting zones of small and medium-sized avalanches. Results show that the proposed method can estimate snow distributions based on a modified terrain parameter Sx(m) and measured snow flux data. It can reproduce patterns of snow redistribution and estimate changes in snow heights reasonably well, as shown by correlation coefficients (R) of 0.78 to 0.86. The derivation of the modified terrain parameter Sx(m) and snow flux are specific to the research site and not yet generally applicable. The formulations require the calibration and alteration of two parameters only for use in studies with other terrain and weather characteristics.