Properties of Blowing Snow,
ROCKY MOUNTAIN FOREST AND RANGE EXPERIMENT STATION FORT COLLINS CO
Pagination or Media Count:
The size and shape of windblown snow particles determine not only the mass transported by turbulent fluxes but also the rate of phase change from ice to water vapor that occurs in this multiphase flow. These properties and particle densities dictate particle fall velocity and therefore the vertical distribution of mass and surface area, which strongly influence the gradients and fluxes of sensible heat and water vapor within the transport layer. Initial movement at the snow surface depends more on availability and impact forces of loose particles than on aerodynamic drag. Cohesion between surface particles and particle restitution coefficient are important properties that determine threshold wind speeds for snow transport. Threshold speeds for blowing snow vary over such a large range in nature that formulations predicting transport rate as a function of wind speed should include threshold speed as a parameter. The expression derived by Iversen et al 1975 is compared with low-level snow transport in the atmospheric boundary layer. Self-similarity of wind profiles in blowing snow is a property of the flow that has been exploited for scale modeling of snow deposition around obstacles, both outdoors and in wind tunnels. Good quantitative results are obtained by careful attention to similitude requirements.