Studies on Blowing Snow II
摘要
In a wind tunnel, several series of measurements of wind velocity were made with small Pitot tubes at different heights above the new fallen snow surface and the surface roughness parameter 0.0045 cm was obtained for the wind speed at the central part of wind tunnel 5.5-10 m/s. In the field, the roughness parameter was the same value 0.0045 cm as in the wind tunnel for the wind speed at 1 m height 5-9 mis, but it became larger with the wind speed, and it became 0.11 cm for the wind speed 13.2 m/s. The relation between the temperature and the threshold wind speed necessary for the occur-rence of blowing snow was obtained by observation in the field. On this rel~tion, a theoretical explanation was attempted. It was also observed in a wind tunnel that the turbulence makes the threshold wind speed lower. The saltation of snow particles was photographed in a wind tunnel and in a field. The illumi-nation by a strobolight made it easy to measure the speed of snow particles on a photograph since a particle made a series of spots on it. Two parallel trenches in a field, perpendicular to the wind direction gave information on the mechanism of the blowing snow. When the interval of two trenches was about 1 m and wind speed was not more than 6 mis, no snow drifted into the leeward trench. But, when the interval was 10 m, and wind speed was not more than 5 mis, the amount of snow drifted in the leeward trench was a half of that drifted in the windward trench. Three types of blizzard meters were set in a field and were compared with each other on their respective collection efficiency. The type for Antarctica was not good, as its mouth was too small and was easily choked with snow.