Range–Height Scans of Lidar Depolarization for Characterizing Properties and Phase of Clouds and Precipitation

Abstract

Backscatter and depolarization lidar measurements from clouds and precipitation are reported as functions of the elevation angle of the pointing lidar direction. The data were recorded by scanning the lidar beam (Nd:YAG) at a constant angular speed of ?3.5° s?1 while operating at a repetition rate of 10 Hz. The scan results highlight known depolarization phenomena in clouds and precipitation, and contribute additional and often essential information for the unambiguous characterization of their liquid, solid, or mixed phase. Moreover, in rain and snow, there is an evident and at times spectacular dependence on the elevation angle. That dependence is very sensitive to crystal type and orientation, or raindrop shape. For the rain case, there is a definite need for calculations of the scattering phase matrix elements for slightly deformed and oscillating spheres because of the real potential for retrieving information on raindrop eccentricity from lidar depolarization scans.