Saltation-layer structure of drifting snow observed in wind tunnel

Abstract

AbstractThe saltation-layer structure of drifting snow was investigated using the wind tunnel in a cold room. Experiments were conducted under various snow-temperature and wind-speed conditions over loose and hard snow covers. Snow was seeded at the upwind end of the wind tunnel. Mass-flux profiles of drifting snow were measured with a snow-particle counter. The theoretical expression for the mass flux of saltating sand (Kawamura, 1948) was fitted to the measured profiles, and two parameters in the theoretical expression, saltation height h0 and mass flux at the surface q0, were determined. The main results are as follows: (1) In the case of hard snow cover, snow particles are hardly ejected and drifting snow is maintained by the seeded snow. The value of h0 linearly increases with wind speed and decreases with snow temperature, and q0 decreases with wind speed and is in proportion to seeding rate. (2) In the case of loose snow cover, erosion occurs under high-wind conditions and the contribution of the ejected snow particles to drifting snow is remarkable. The h0 linearly increases with wind speed, but its value is smaller than the value over hard snow cover. Due to erosion, q0 increases with wind speed. Snowdrift transport rate and q0 do not change with seeding rate under low-wind conditions, because the drifting snow is saturated. Under high-wind conditions, however, both snowdrift transport rate and q0 slightly increase with seeding rate.