On Depolarization Lidar-Based Method for the Determination of Liquid-Cloud Microphysical Properties
Defence Research and Development Canada Valcartier Quebec, Quebec Canada
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Under single scattering conditions, water droplets clouds do not depolarize the backscattered light. However, backscattered light from multiple scattering will be depolarized. The level of depolarization is a function of the droplets size, the cloud extinction coefficient value and profile it has also an important dependency on the lidar field-of-view FOV. The use of depolarization information to retrieve cloud microphysical properties, using Multiple-FOV has been the object of studies, 1, 2. Recently the use of the depolarization, at a single FOV, has been studied for cloud with linear liquid water content profiles, 3, 4. In this paper we present the mechanism leading to depolarization and identify the FOV values for which the information on particle size is high. Also Monte Carlo simulations for cloud with constant and ramp up profiles are presented. The degree of linear depolarization as a function of cloud penetration is significantly different for both cloud profiles. This suggests that the use of the degree of linear depolarization at a single FOV should be used with caution to determine clouds micro-physical parameters.