P39  Anthropogenic Influences on Asian Monsoon: Land-use Change vs. Short-lived Air Pollutants

Jiang, Xiaoyan, Mary C. Barth, Alex E. Guenther, Louisa Emmons, and Christine Wiedinmyer, National Center for Atmospheric Research, USA

Anthropogenically-induced land-use/land cover change has been identified as a significant forcing that can impact Asian monsoon precipitation characteristics through altering the surface Bowen ratio, boundary layer processes, and land–atmosphere coupling. Aerosols, in particular those related to anthropogenic activities, including black carbon, organic carbon, and sulfate aerosols, have been found to affect the Asian monsoon through direct and indirect aerosol radiative forcing. In this work, we use the coupled regional Weather Research and Forecasting model with Chemistry (WRF-Chem) to understand and compare how these changes caused by human activities could modulate the Asian monsoon system (i.e., monsoon development and evolution). A series of 6-month WRF-Chem sensitivity experiments have been carried out, and the modeling results are evaluated against reanalysis data and satellite observations. When considering the aerosol radiative forcing, in particular the indirect radiative forcing, the model performs well in simulating monsoon season rainfall over India, East China, and some regions in South Asia where the air is heavily polluted. The impacts on precipitation due to land use change are smaller as compared to the impacts of aerosols. Detailed analysis regarding the changes in radiation, surface fluxes, atmospheric heating, and circulation patterns due to land-use change and aerosols are presented to further explain the roles of short-lived air pollutants versus land-use change in the Asian monsoon system.