Doppler Radar Observation of Wind Structure in Snow

Abstract

Sinusoidal variations in the longitudinal speed of the wind in the planetary boundary layer are observed with a C-band multiple-gate Doppler radar using snow as a wind tracer. These undulations in the horizontal wind are believed to be orographically generated wave phenomena. The observed wind structures have average scale lengths of 300 m and their amplitude decreases with altitude. The propagation speeds of the, wind structures have been determined with a spatial correlation technique and have, at times, been found to depart appreciably from the mean ambient wind. Under stable atmospheric conditions the wind structures persist for a considerable period. In one extreme case the structures preserved identifiable characteristics during advection over a distance of 9 km. This remarkable persistence resulted in a Lagrangian-Eulerian time-scale ratio of 45.