The difference and linkage between aerosol direct and indirect effects on precipitation over Southeast Asia during summer 2015

The rapid economic development and urbanization has enhanced the anthropogenic emissions over Southeast Asia, which drew great attention on the aerosol influence on its precipitation. Four simulations are conducted on summer 2015 using WRF-Chem to explore the aerosol direct effect (ADE) and aerosol indirect effect (AIE) on precipitation over Southeast Asia. The research is aiming to compare and discuss the land-sea difference between two effects and their mechanisms of influences. Based on the comparison analysis, it is showed that 1. Including the chemistry processes in the model improves the simulation to a limited extent; 2. ADE and AIE influence precipitation in an inverse way. ADE induces larger changes in precipitation than AIE and shows great land-sea difference; 3. ADE cools and enhances downward motion over the land surface and increases water vapor via aerosol absorption, which leads to suppressed precipitation and smaller rain radius; 4. AIE enhances the conversion of cloud water into rainwater and heats the land surface via cloud reduction, which leads to an enhancement in upward motion and precipitation.