Dust-aerosol optical modeling with Gaussian spheres: Combined invariant-imbedding T-matrix and geometric-optics approach

Abstract

The Gaussian sphere has been widely used as a model to study light scattering by irregular particles; and, despite extensive numerical studies, the optical properties are not thoroughly understood. Based on Gaussian spheres and using a combination of the invariant imbedding T-matrix method and an improved geometric-optics method, the single-scattering properties (namely, the 4×4 phase matrix, extinction cross section, single-scattering albedo, and asymmetry factor) are computed in the Rayleigh to geometric optics regimes. The simulations are performed with various degrees of irregularity, and the effects of particle irregularities are investigated over a wide range of particle sizes. Furthermore, the theoretical simulations based on Gaussian spheres are used to fit the measured optical properties of feldspar particles from the well-known Amsterdam–Granada light scattering database. A mixture of several shapes is shown to closely reproduce the measured phase matrices. The results may be potentially useful for remote-sensing and radiative-transfer applications involving dust aerosol.