Assessing the Non-Sphericity and Inhomogeneity Effects of Sea Salt Aerosols in Light Scattering and Radiative Transfer

The non-sphericity and inhomogeneity of marine aerosols have not been well addressed in radiative transfer calculations and remote sensing studies. This talk reports on recent studies on the optical properties of non-spherical and inhomogeneous sea salts. Dry sea salt aerosols are modeled based on cube-like super-ellipsoidal geometries with a prescribed aspect ratio and roundness parameter. Due to the hygroscopicity, sea salt particles grow with increasing humidity. Wet sea salt particles are modeled as coated super-ellipsoids, as spherical particles with a super-ellipsoidal core, and as homogeneous spheres depending on the level of relative humidity. We found that the non-sphericity and inhomogeneity of marine aerosols have to be accounted for in interpreting Lidar backscattering signals. In addition, we found the effect of inhomogeneity on optical properties is pronounced for coarse-mode sea salts, which has significant impact on the asymmetry parameter. These findings have important implications for atmospheric radiative forcing assessment involving sea salt aerosols, which will be illustrated with the CESM (Community Earth System Model) results.