Modeling of the Second Indirect Effect of Anthropogenic Aerosols in East Asia

This study investigated the second indirect climatic effect of anthropogenic aerosols, including sulfate, organic carbon (OC), and black carbon (BC), over East Asia. The seasonal variation of the climatic response to the second indirect effect was also characterized. The simulation period for this study was 2006. Due to a decrease in autoconversion rate from cloud water to rain as a result of aerosols, the cloud liquid water path (LWP), and radiative flux (RF) at the top of the atmosphere (TOA) changed dramatically, increasing by 14.3 g m-2 and decreasing by -4.1 W m-2 in terms of domain and annual average. Both LWP and RF changed most in autumn. There were strong decreases in ground temperature in Southwest China, the middle reaches of the Yangtze River in spring and autumn, while maximum cooling of up to -1.5 K occurred in the Chongqing district. The regional and annual mean change in ground temperature reached -0.2 K over eastern China. In all seasons except summer, precipitation generally decreased in most areas north of the Yangtze River, whereas precipitation changed little in South China. Precipitation changed most in summer, with alternating bands of increasing (~40 mm) and decreasing (~40 mm) precipitation appearing in eastern China. Precipitation decreased by 1.5-40 mm over large areas of Northeast China and the Huabei Plain. The domain and annual mean change in precipitation was approximately -0.3 mm over eastern China. The maximum reduction in precipitation occurred in summer, with mean absolute and relative changes of -1.2 mm and -3.8% over eastern China. This study revealed considerable climate responses to the second indirect effect of aerosols over specific regions of China.