Aerosol Impacts on Clouds and Regional Climate in Southeast of China– Results from Bin and Bulk Microphysics

Two different cloud systems – deep convective clouds (DCC) and stratocumulus (SCu), observed during the DOE ARM Mobile Facility (AMF) field campaign to study the aerosol indirect effects in China (AMF-China), are simulated with the Weather Research and Forecasting (WRF) model, using an explicit bin microphysics and a two-moment bulk microphysics scheme. For the first time, extensive measurements of aerosol and cloud properties were acquired in China that can be used to validate model simulations to better understand aerosol indirect effects in China. We find that aerosols can significantly change the spatial and temporal distributions of precipitation in the DCC system, but the change in the stratiform cloud regime is not as significant. Aerosols also significantly delay the development of the cloud system and precipitation, increase droplet and ice particle number concentrations, decrease the hydrometeor size, and increase the anvil area in the DCC system. Aerosol is found to reduce wind speed and temperature near the surface in the morning but increase them in the afternoon until evening, with larger magnitudes in the DCC. Our results show that aerosols in China significantly change the timing of storms, surface sensible and latent heat fluxes, precipitation rate, and the regional climate of southeastern China. The Morrison two-moment microphysics is able to simulate the cloud system reasonably well, but has poorer performances in simulating the timing of precipitation, precipitation rate, and cloud properties observed at the AMF site compared to the bin microphysics. Aerosol effects simulated by the two-moment bulk scheme are similar to those of the explicit bin microphysics for the SCu, but different for the DCC system. Suggestions in improving bulk parameterizations will be discussed.