The Polarization Characteristics of Lidar Scattering from Snow and Ice Crystals in the Atmosphere

Abstract

The effects of ice crystals on the backscatter polarization in lidar returns have been measured. Scattering from ground-level snow of varying density, high-altitude cirrus clouds and ice pellet shower clouds has been studied using a linearly polarized ruby laser system with multiple receiver channels. The space and time dependence of the total intensity and the linear depolarization ratio δ of the lidar return have been investigated. It has been found that considerable variations occur in snow with δ varying between 0.2 and 0.8. In cirrus and ice pellet shower clouds δ is typically found to lie in the range 0.3 ± 0.1. The factors involved in the use of polarization data for ice-water discrimination in the atmosphere are presented and discussed.