Influence of aspect ratio on the light scattering properties of spherical aerosol particles

Abstract

The influence of aspect ratio on the light scattering properties of ellipsoidal particles is studied by using T-matrix method and discrete ordinate method in this paper. The light scattering characteristic quantities including extinction efficiency, asymmetrical parameter, single scattering albedo, scattering phase matrix, and bidirectional reflectance distribution function (BRDF) are computed. It is found that light scattering properties of ellipsoidal particles are sensitive to aspect ratio. The aspect ratio can influence the oscillation frequencies and amplitudes of the scattering parameters except some special size parameters. The value of asymmetrical factor could be as large as 0.3 in wave crest value of size parameter while it is no more than 0.1 at the balance location. As for the multiple scattering, the characteristics of BRDF for different aspect ratios in different incident angles and optical thickness values are analyzed, and for a further study, the relative differences of BRDF influenced by aspect ratio, optical thickness, and incident angle are analyzed. The results show that the variation trends of BRDF for the ellipsoidal particles with various aspect ratios are basically the same. However, the curve of BRDF of spherical particles (i.e., with their aspect ratios being 1) is more variable. With the increasing of aerosol optical thickness and aspect ratio, the curves of BRDF at different aspect ratios for ellipsoidal particles tend to a steady and similar value and the relative difference of BRDF decreases. But with the increasing of aerosol optical depth, the relative difference of BRDF increases with the increasing of incident angles, especially in large optical thickness, the value of the relative difference of BRDF can be as large as 15%.