Threshold wind velocity for snow drifting as a function of terminal fall velocity of snow particles

The threshold wind velocity V T for snow drifting depends on the snow particle shape and its surface condition. To explain the effect of particle shape on V T , we employ the terminal fall velocity of snow particles, which, similar to V T , depends on the aero resistance coefficient. For snow samples obtained from a natural snow surface, V T was measured by a wind tunnel experiment, and the terminal wind velocity w was measured in a cylinder. In addition, the repose angle was also observed. For estimating the friction between the particles, V T and w were considered to be dependent on particle shape. For a dendrite crystal, V T and w were determined to be 3-7 m/s and 0.4-0.9 m/s, respectively; further, V T tended to be proportional to w. The V T /w ratio of other particles was larger than that of the dendrite crystals; this is explained by the existence of a bonding force.