Sensitivity analysis of morphology on radiative properties of soot aerosols.

Absorption cross section (Cabs), scattering cross section (Csca) and asymmetry parameter (ASY) of soot particles in different atmospheric aging status were investigated under fixed equivalent volume radius (RV) using the numerically exact multiple-sphere T-matrix method. The radiative properties of soot particles would be largely diverse in different aging status even RV is fixed. However, there are many insensitive parameters under different aging status. The Cabs and ASY is insensitive to monomers number (Ns) when Ns is larger than a threshold value. For bare and thinly coated soot aggregates, Cabs is insensitive to fractal dimension (Df) when the RV is small, where the relative errors of Cabs for different Df are within 2.5%. However, the effects of Df is obvious for large soot due to the shielding effects of large monomers, and the relative errors for different Df can reach to 18% for bare soot. For thinly coated soot, the changes of ASY with soot volume fraction (fsoot) is small due to the little changes of the fractal structure when the RV is fixed. In addition, for thickly coated soot, ASY is insensitive to Ns due to the unchanged overall spherical structure. Our results give a further understanding of the influences of morphology on radiative properties. It may be helpful for model selection and model simplification.