Three-wavelength polarization Scheimpflug lidar system developed for remote sensing of atmospheric aerosols.

Abstract

Multiple-wavelength polarization lidar techniques have been of great interest for the studies of aerosol backscattering color ratio, Ångström exponent, particle size distribution, hygroscopic growth, etc. Conventional lidar techniques are mainly based on the time-of-flight principle. In this paper, a three-wavelength polarization Scheimpflug lidar (SLidar) system, based on the Scheimpflug imaging principle, has been developed for studying optical properties of atmospheric aerosols. The SLidar system utilizes low-cost, compact, multimode laser diodes as light sources and two complementary metal oxide semiconductor (CMOS) sensors as detectors. The depolarization ratio was measured at the 808 nm band by successively detecting atmospheric backscattering signals from two orthogonally polarized laser beams with a polarization CMOS camera, while the 520 nm and the 405 nm backscattering signals were recorded by a second CMOS camera based on the time-multiplexing scheme. Atmospheric remote measurements were carried out in May and July 2019 on a near-horizontal path. The aerosol extinction coefficient, linear volume depolarization ratio, and the Ångström exponent have been retrieved and evaluated to study aerosol properties during different atmospheric conditions, which were in good agreement with optical properties reported by previous studies.