The role of a mid-air collision in drifting snow

Abstract. Drifting snow, a common two-phase flow movement in high and cold areas, contributes greatly to the mass and energy balance of glacier and ice sheets and further affects the global climate system. Mid-air collisions occur frequently in high-concentration snow flows; however, this mechanism is rarely considered in current models of drifting snow. In this work, a three-dimensional model of drifting snow with consideration of inter-particle collisions is established; this model enables the investigation of the role of a mid-air collision mechanism in openly drifting snow. It is found that the particle collision frequency increases with the particle concentration and friction velocity, and the blown snow with a mid-air collision effect produces more realistic transport fluxes since inter-particle collision can enhance the particle activity under the same condition. However, the snow saltation mass flux basically shows a cubic dependency with friction velocity, which distinguishes it from the quadratic dependence of blown sand movement. Moreover, the snow saltation flux is found to be largely sensitive to the particle size distribution since the suspension snow may restrain the saltation movement. This research could improve our understanding of the role of the mid-air collision mechanism in natural drifting snow.