Structures of snow cloud in dry-snow avalanches

Abstract

During two winter seasons, we observed avalanche winds and the air movement in the snow dust region. The wind velocity near the avalanche front was comparable to the averaged internal velocity of the front region. The avalanche wind blew down the valley. However, there was a rising air current just before the avalanche front. The wind velocity and direction showed a periodic change in the snow cloud region, from which the size of the ordered structure (vortex) was estimated to be 35–70 m. The density of the frontal part of one avalanche was estimated to be 1.9–3.8 kg m −3 .