Aerosol optical properties during coagulation and condensation in multimodal aerosol size distribution

The aerosols in the atmosphere continuously change their size and composition through the dynamic processes such as coagulation or condensation. For example, the Brownian motion of particles, turbulence, presence of a shear field, aerosol particle growth with the accretion of monomers on existing particle, and external forces such as gravity and electrical forces could cause coagulation. This means that the change of the size distribution due to coagulation and condensation process affect Ångstrom exponent. For this reasons, the aerosol dynamics play an important role in estimating optical properties such as Ångstrom exponent. Usually, the atmospheric aerosol shows the multimodal distribution (such as bimodal or three modal distribution). In this study, the change of the Ångstrom exponent for polydispersed aerosol size distribution during the aerosol dynamic processes was investigated. Multimodal Log-normal aerosol size distribution was assumed and the sensitive analysis of the Ångstrom exponent during the coagulation and condensation process was performed. The sensitivities of coarse mode particles are analyzed in order to find the effect of dust particles on optical properties with large particle size such as Asian dust. This study also investigated the sensitivity of aerosol refractive index to analyze the Angstrom exponent due to aerosol composition change during the aerosol dynamic process. The results showed that the Ångstrom exponent changes sensitively as a function of multimodal size distribution and refractive index.