Modeling the radiative properties of nonspherical soil-derived mineral aerosols

Mineral dust aerosols have complex nonspherical shapes and varying composition. This study utilizes data on morphology (size and shape) and composition of dust particles to determine the extent to which the optical properties of real particles differ from those of spheres. A method for modeling the optical properties of complex particle mixtures is proposed. The method combines dust particle composition-shape-size (CSS) distributions reconstructed from the electron microscopy data, effective medium approximations and discrete dipole approximation. The method is used to compute optical characteristics of realistic dust mixtures representative of Saharan and Asian dust. We demonstrate that considered CSS distributions result in various differences in the extinction coefficient, single scattering albedo, asymmetry parameter and the scattering phase function relative to the volume-equivalent spheres and the mixtures of the randomly oriented oblate and prolate spheroids. Implications of these differences for radiation/climate modeling and remote sensing are discussed. (C) 2003 Elsevier Ltd. All rights reserved.