Abstract

Our lidar investigations of clouds and of particulate suspensions have revealed some interesting features of multiple scattering that could be exploited to infer size information from backscatter polarization measurement.¹ The total multiple scattering in the backscatter field shows a characteristic build-up with pulse penetration and with increase in attenuation coefficient. However, the distribution of multiple scattering, polarized parallel and perpendicular to the polarization direction of the linearly polarized transmitted pulse, is found to be anisotropically distributed in the region surrounding the illuminated volume. This anisotropy is found to have a relationship with the size of the scattering particles and the probing wavelength. For sizes comparable to the wavelength the parallel polarized backscatter intensity is found to concentrate along the direction of polarization and orthogonal to it with the regions at azimuths of 45° showing very low intensity. The cross-polarized backscatter however shows intensity concentrated along the 45° directions with minima of intensity along and orthogonal to the initial polarization direction.