A comparative study on scattering properties of aerosols with different aggregation patterns

Aerosol particles suspended in the atmosphere naturally aggregate to form various morphologies, which significantly impact atmospheric radiation transmission. This paper investigates the impact of particle mixing states on the scattering phase function of chain-like atmospheric aerosol aggregates using the Generalised Multiparticle Mie (GMM) method. The scattering properties of dust aerosol particles arranged in triangular (T-3), L-shaped (L-3), and square (S-4) configurations are compared with their envelope-equivalent spheres. The analysis considers the impacts of individual particle size and incident wavelength. Building upon effective medium theory, this study further investigates the scattering property ratios between T-3 dust aggregates and their envelope-equivalent spheres in urban and rural environments. The results indicate that the difference in particle size within a chain determines the magnitude of scattering phase function. At specific size parameters, T-3 aggregate achieves SSA equivalence with its envelope-equivalent spheres, while L-3 and S-4 morphologies demonstrate optical equivalence, in extinction, scattering, and SSA values with their corresponding equivalent spheres under certain conditions. Size parameter and aggregation morphology significantly influence the phase function ratios between aggregates and their envelope-equivalent spheres. Environmental (urban/rural) influences on the phase function ratio are minimal within size-dependent forward scattering ranges, suggesting that primary particle diameter determines the angular region where environmental effects can be neglected. These findings contribute to understanding the impact of atmospheric aerosol aggregates on radiation transmission and provide theoretical support for the retrieval of atmospheric aerosols.