Abstract
Dry snow avalanches generally consist of a dense flowing layer near the bottom and a snow cloud, however, the detailed internal structure is still poorly known. The airborne snow flow experiments were carried out using up to 240 kg of snow at the Miyanomori ski jump hill, Sapporo. The velocity of the flow reached more than 15 m/s and the snow cloud developed up to 40 cm in height. Snow balls rolled and saltated sparsely at the leading edge, then the main part of the flow, which was composed of the flowing layer and a well developed snow cloud followed. Not only the fluidized snow but also a number of snow balls were found in the flowing layer. At the tail, the two-layer structure was still maintained but the snow balls and height of the snow cloud decreased and the flow became intermittent. In the main part, the flowing layer ran faster than the snow cloud, while at the tail, the flowing layer decelerated and the speed of the snow cloud become faster. The densities of the fluidized snow at the main part and the tail were 10-40 kg/m3 and 40-70 kg/m3 respectively.The spectrum analysis implied the existence of characteristic structures 1.5-4 m long, in the flow.
