PNNL

Abstract

Aerosol optical properties can be approximated in terms of analytic functions of the wet surface mode radius with coefficients that can be related to the wet refractive index. The wet radius is diagnosed from the dry radius and relative humidity using the Kohler theory. The wet refractive index is diagnosed from the volume fractions and refractive indices of all components of the aerosol, including water, using volume mixing for soluble components and an effective medium approximation for the insoluble components. The parameterization is evaluated by comparing with Mie solutions for highly scattering and highly absorbing aerosol for a wide range in size distributions and relative humidity. Errors are often less than 10% and are less then 30% for all conditions except when absorption is negligible. The parameterization is suitable for any aerosol model that uses log-normal size distributions composed of internal mixtures of multiple aerosol components.