Foehn is snow-eater; Numerical analysis of snowmelt and CO exchange processes at pre-alpine grassland sites

Katata, Genki; Mauder, M.*

A multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) was modified to simulate snow and frozen soil processes. Heat and liquid water transported within a multi-layer snow structure scheme, and freeze-thaw process of soil water was incorporated into the model. The modified model was applied to pre-alpine grassland sites in TERestrial ENvironmental Observatories (TERENO) networks in Germany. The modified model reproduced the overall temporal changes in observations of momentum, surface energy, and CO fluxes, albedo, physical snow depth and surface temperature, and soil temperature and moisture. Our simulations demonstrated that foehn winds, a southern warm and dry downslope wind of the Alps, strongly enhanced snow melting due to large negative sensible and positive latent heat fluxes. Soon after the snow melted due to foehn winds, CO assimilation immediately occurred even in the middle of winter season.