Moisture fluxes over snow with and without protruding vegetation

The sublimation of snow and evaporation of melted snow is contrasted between brush, grass and bare ground sites using eddy-correlation data. Averaged over the entire winter season, the evaporation/sublimation is about 20% greater over the brush site than the bare ground site, apparently due to greater supply of snow. Blowing snow collects in patches of brush, which protrude above the snow. This study evaluates commonly used simple formulations of the surface moisture flux including two versions of the bulk aerodynamic formula and the stability-dependent Penman and Penman-Monteith methods for predicting evaporation/sublimation. The evaluation is based on eddy-correlation data from the three sites with conditions ranging from snow-free to snow-covered ground surfaces. The water availability factors, required for these formations, increase with snow-fraction coverage, but less so with melting conditions, depending on site and formulation. Various influences on the sublimation/evaporation are examined and the performance and shortcomings of each formulation are assessed.