ABSTRACT. Wind tunnel measurements of snowdrift in a turbulent, logarithmic velocity boundary layer have been made in Davos, Switzerland, using natural snow. Regression analysis gives the drift threshold friction velocity (u Ãt ), assuming an exponential drift profile and a simple drift to friction velocity relationship. Measurements over 15 snow covers show that u Ãt is influenced more by snow density and particle size than by ambient temperature and humidity, and varies from 0.27 to 0.69 m s

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[1] Experiments in a cold wind tunnel were used to verify drifting snow sublimation models. A layer of drifting snow particles was formed over a sintered snow surface. Sublimation and drifting snow flux were estimated from two vertically resolved profile measurements separated along the flow path and were compared to a simple, onedimensional diffusion model of drift and drifting snow sublimation. The experiments show an increase in water vapor content of the air from drifting snow sublimation. The measured drifting snow sublimation appeared to be consistent with albeit somewhat larger than theoretical values found in the model study. Under wind tunnel conditions, particle number density appears to be the most important controlling factor on the sublimation rate. For experiments with external solar radiative forcing, the increase of the sublimation rate was also larger than theoretical predictions. The experiments suggest that irregular snow crystals and solar radiation might increase sublimation rates more than described by many drifting snow models.

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