Impact of windflow calculations on simulations of alpine snow accumulation, redistribution and ablation

Wind redistribution, radiation and turbulent heat fluxes determine seasonal snow accumulation and melt patterns in alpine environments. Mathematical representations of windflow vary in complexity and introduce uncertainty to snow modelling. To characterize this uncertainty, a spatially distributed snow model that considers the physics of blowing snow transport and sublimation and the energy fluxes contributing to snowpack ablation were evaluated for its ability to simulate seasonal snow patterns around a windy alpine ridge in the Canadian Rockies. The model was forced with output from three windflow models of varying computational complexity and physical realism: (i) a terrain-based empirical interpolation of station observations, (ii) a simple turbulence model and (iii) a computational fluid dynamics model. Compared with wind measurements, the windflow simulations produced similar and relatively accurate (biases lower than +/- 1.1 ms(-1)) wind speed estimates. However, the snow mass budget simulated by the snow model was highly sensitive to the windflow simulation used. Compared with measurements, distributed snow model depth and water equivalent errors were smallest using either of the two turbulence models, with the best representation of downwind drifts by the computational fluid dynamics model. Sublimation was an important mass loss from the ridge, and windflow model choice resulted in cumulative seasonal sublimation differences ranging from 10.5% to 19.0% of seasonal snowfall. When aggregated to larger scales, differences in cumulative snowmelt and snow transport were negligible, but persistent differences in sublimation and snow-covered area suggest that windflow model choice can have significant implications at multiple scales. Uncertainty can be reduced by using physically based windflow models to drive distributed snow models. Copyright (c) 2015 John Wiley & Sons, Ltd.