Effect of relative humidity and particle shape on the scattering properties of sea salt aerosols

According to the hygroscopic characteristics and different forms of sea salt particles in different relative humidity conditions, the models of sea salt particles under three conditions were established:low humidity(RH=0%), medium humidity(RH=50%), high humidity(RH=95%). Influence of relative humidity and particle morphology on the scattering characteristic of sea salt was studied by discrete dipole approximation (DDA) method. Influence of relative humidity and particle morphology on the scattering and radiation characteristic of sea salt was studied by DDA method, Mie scattering theory and Discrete Ordinate Method Radiative Transfer (DISORT) method. The results show that relative humidity and particle morphology have great influence on the scattering characteristics of sea salt particles. Under medium relative humidity, the scattering and radiative transfer characteristics of the sea salt aerosol are more sensitive to particle shape. When the optical thickness is equal to 0.1, the relative difference of BRDF of spherical-cubic sea salt model can be more than 15%, the effect of relative humidity and particle morphology must be taken into account when studying the scattering and radiation transfer properties of sea salt aerosol. With the increase of optical thickness, the relative difference of BRDF decreases, when the optical thickness is greater than 1, the relative difference of BRDF is less than 5%, the equivalent sphere method can be used to simulate calculation within a certain precision range. These findings have important implications to the theory and application of atmospheric aerosol scattering and radiation transfer.