Scattering of Polarized Laser Light by Water Droplet, Mixed-Phase and Ice Crystal Clouds. Part II: Angular Depolarizing and Multiple-Scattering Behavior

Abstract

Light scattering measurements obtained with a polar nephelometer in the planes of polarization both orthogonal and parallel to that of the linearly polarized laser source are used to investigate the angular depolarizing properties of artificial ice, water and mixed-phase clouds in Part II of this report. Although the generation of depolarized energy in water and ice clouds is shown to be accomplished by different scattering mechanisms, angular depolarization patterns for both cloud types display the tendency for linear depolarization ratios (δ, the ratio of orthogonal to parallel polarized signals) to increase with increasing scattering angle. For ice clouds, however, the δ values are typically an order of magnitude or more greater than the values for water clouds as a consequence of cloud particle shape effects. Angular depolarization measurements of mixed-phase clouds are shown to possess the potential for determining a measure of cloud ice-water balance by means of bistatic remote sensing observations. Moreover, the backscattering characteristics of water and ice clouds have been examined with the aid of observations performed at a scattering angle of 175° for application to monostatic lidar studies.