Asian aerosol assimilation and regional aerosol radiative forcing, using reanalyses, regional models and satellite data

We summarize a state-of-the-art aerosol assimilation effort aimed at recreating the 4D aerosol (including dust and anthropogenic aerosols) heating rates and surface solar fluxes in Asia. This project was launched to better understand aerosols, their radiative forcing and regional climatic impacts in Asia. The PNNL regional model was used to provide meteorology. Satellite and ground based data were integrated for AOD &SSA data. The Iowa aerosol/chemistry model STEM-2K1 assimilated AOD &SSA observations into their model bound by the PNNL meteorology, and produced 2001-2004 aerosol simulations at the 0.45°x0.4° resolution. In the vertical there are 23 layers in the troposphere. We used the aerosol simulations and the regional model simulated meteorology to calculate anthropogenic aerosol radiative forcing with an updated Monte-Carlo Aerosol Cloud Radiation (MACR) model. The PNNL regional model is used again with this forcing to assess the climatic effects of Asian anthropogenic aerosols. The 4 year climatological monthly mean anthropogenic aerosol forcing ranges from -20 Wm-2 to +10 Wm-2 (TOA), from +2 Wm-2 to +50 Wm-2 (atmosphere) and from -57 Wm-2 to -3 Wm^{- 2} (surface). In the vertical, the aerosol forcing is mainly concentrated below 650hPa and diminishes slowly towards 200hPa. At the 775hPa level, the forcing often exceeds 1.0 K/day. At this level, the forcing is largest in winter but its interannual variation is larger in fall. Most of the forcing is around South Asia, Southeast Asia, the eastern China and nearby oceans.