Atmospheric aerosols affect regional meteorology and long-term climate through climate-chemistry-aerosol-cloud-radiation interactions. The impacts of aerosol feedbacks, from direct impacts on radiation to indirect effects by acting as cloud condensation nuclei and modifying cloud properties, strongly depend on the number and mass concentrations as well as size distribution of aerosols. As a major source of new particles in the atmosphere, homogeneous nucleation is a key process in determining the number concentration and size distribution of aerosols. The fully-coupled Weather Research and Forecasting model with Chemistry (WRF/Chem) provides a powerful tool to simulate the direct and indirect effects of aerosols that are sensitive to aerosol treatments. Homogeneous nucleation is simulated in WRF/Chem based on the Wexler's classical binary H2SO4-H2O homogeneous nucleation (BHN) parameterization. Several BHN and ternary homogeneous nucleation (THN) parameterizations that are based on more advanced theories have been developed in recent years. In this study, a binary module based on a kinetic quasi-unary nucleation (QUN) treatment and a new kinetic ternary H2SO4-H2O-NH3 nucleation module will be first tested in a box model and then incorporated into WRF/Chem.

WRF/Chem with new and default nucleation modules will be applied over East Asia that covers most of China as well as Japan, Korea, and part of Mongolia, India, and some Southeast Asian countries. The horizontal and vertical grid resolutions are 36-km and 30 layers, respectively. The simulated periods are January and July, 2005. The simulations will be evaluated using surface and satellite observations. An intercomparison of model simulations with different nucleation modules will be conducted to analyze the impacts of simulated number concentrations and size distributions of aerosols on radiation, cloud properties, and other meteorological variables.