Simulation of the influence of coarse mode particles on the properties of fine mode particles

The effects of coarse mode particles on aerosol dynamics with simultaneous processes are investigated by applying the modal approach, The Brownian coagulation and condensation processes are considered for an aerosol system with three modal aerosol distributions to simulate how the distribution changes when the coarse mode number concentration increases. Simulation results show that during the Brownian coagulation process, the number concentration in the nuclei and accumulation mode decrease due to inter-modal coagulation of the nuclei, accumulation and coarse modes particles. This inter-modal coagulation process is enhanced when the number concentration of the coarse mode increases, such as in dust storm events. It means that the coarse mode can influence on the nuclei and accumulation mode significantly, especially, when the number concentration of the coarse mode becomes large. For the case of gravitational coagulation, the intra-modal coagulation of coarse mode particles makes the number concentration to decrease, while the inter-modal gravitational coagulation between fine modes and coarse mode is negligible. (C) 2002 Elsevier Science Ltd. All rights reserved.