A snowdrift index based on SNOWPACK model calculations

Abstract

The SNOWPACK model developed at the Swiss Federal Institute for Snow and Avalanche Research is a one-dimensional momentum, mass- and energy-balance model. Its current version includes important features such as a numerical solution of the instationary heat-transfer and creep/settlement equations, a complete surface-energy balance, phase changes, water transport and snow microstructure development (metamorphism). The micro-structural parameters are linked to the thermal conductivity and the snow viscosity. The new snowdrift routine uses the modelled snow to determine a threshold friction velocity. The drift model describes the local mass flux of snow, distinguishing between a saltation and suspension contribution. The snow-cover model adapts to erosion (or deposition) due to drifting and blowing snow. The drift formulation improves the seasonal snow-cover simulation considerably for stations that show a significant influence of snow transport. From the mass-flux calculation, a snowdrift index results that provides valuable information on local snowdrift for avalanche warning.