Depolarization and Polarization of Light Scattering by Dustlike Tropospheric Aerosols

Abstract

Measurement of the polarization and depolarization characteristics of light scattering by aerosols is a powerful remote sensing technique for retrieving the microphysics of aerosol particles. In this paper, we model dust-like aerosols using mixtures polydisperse, randomly oriented spheroids with varying aspect ratios from 0.6 μm to 2.0 μm at the wavelength of 0.443 μm and 0.865 μm. The Stokes scattering matrix elements averaged over wide shape distributions of spheroids are compared with those computed for polydisperse randomly oriented single scattering spheroids. The shape-averaged phase function for a mixture of spheroids is smooth, featureless, and nearly flat at side-scattering angles and closely resembles those typically measured for natural sand and dust particles. The linear and circular depolarization ratios were computed using the rigorous T-matrix method. We also show that there is no simple relationships between the depolarization ratio and aspect ratio, and an single spheroidal shape particles cannot be used to model natural dust aerosols.