PNNL

Abstract

Polarization-sensitive detection of elastic backscatter is useful for detection of cloud phase and depolarizing aerosols. The U.S. DOE Atmospheric Radiation Measurements (ARM) Program has deployed micropulse lidar (MPL) for over a decade, but without polarized detection. Adding an actively-controlled liquid crystal retarder provides the capability to identify depolarizing particles by alternately transmitting linearly and circularly polarized light. This represents a departure from established techniques which transmit exclusively linear polarization or exclusively circular polarization. Mueller matrix calculations yield simple relationships between the well-known linear depolarization ratio dlinear, the circular depolarization ratio dcirc, and the hybrid MPL depolarization ratio dMPL. This research was supported by the Office of Biological and Environmental Research of the U.S. Department of Energy as part of the Atmospheric Radiation Measurement Program.