Polarization Diversity Lidar Returns from Virga and Precipitation: Anomalies and the Bright Band Analogy

Abstract

Polarization measurements have been obtained with lidar from ice virga and precipitation. Linear depolarization ratios are characteristically near 0.5 for the ice phase, but can display significantly higher values under some conditions. Such anomalous occurrences appear to result from the interrogation of populations of oriented ice crystals, and also as a consequence of the geometry of the monostatic lidar system when viewing targets at short ranges. In agreement with continuous wave laser scattering measurements, melting snowflakes produce a depolarization bright band analogous to that observed with microwave radar, yielding depolarization ratios up to ?0.7 a few hundred meters below the freezing level.