Indirect Radiative and Climatic Effects of Sulfate and Organic Carbon Aerosols over East Asia Investigated by RIEMS

The indirect radiative and climatic effects of sulfate and organic carbon aerosols over East Asia were investigated using a Regional Integrated Environment Model System (RIEMS) with an empirical aerosol-cloud parameterization. The indirect radiative forcing was negative and ranged from -9-0 W m-2 in the domain. The maximum cooling, up to -9 W m-2, occurred in the Chongqing District in winter, whereas the cooling areas were larger during summer than in winter. Organic carbon (OC) aerosols were more abundant in winter than in summer, whereas the sulfate concentration during summer was much higher than during winter. The concentrations of sulfate and OC were comparable in winter, and sulfate played a dominant role in determining indirect radiative forcing in summer, whereas in winter, both sulfate and OC were important. The regional mean indirect radiative forcings were -0.73 W m-2 and -0.41 W m-2 in summer and winter, respectively. The surface cooling caused by indirect effects was more obvious in winter than that in summer. The ground temperature decreased by ~1.2 K in most areas of East China in winter, whereas in summer, the temperature decreased (~-1.5 K) in some regions, such as the Yangtze River region, but increased (~0.9 K) in the areas between the Yellow and Yangtze Rivers. In winter, the precipitation decreased by 0-6 mm in most areas of East China, but in summer, alternating bands of increasing (up to 80 mm) and decreasing (~-80 mm) precipitation levels appeared in East China.