Remote influence of South Asian black carbon aerosol on East Asian summer climate

The remote impact of South Asian black carbon (SABC) aerosol on East Asian summer monsoon (EASM) was studied and compared with the local impact of local East Asian black carbon (EABC) by using ensemble sensitive experiments in atmospheric general circulation model, GFDL AM2.1. The results show that SABC causes a south-north tripolar precipitation response pattern over East Asia. This includes reduced rainfall over a central area from the Yangtze River valley to East China Sea and southern Japan but intensified rainfall over a northern domain ranging from northern China/Korea to northern Japan as well as over a southern domain, southern China. Such SABC induced changes are about 5-10% of the observed climatological rainfalls in East Asia. Mechanistically, such a remote effect is realized through a propagating wave train along the Asian upper tropospheric jet. The wave train disperses South Asian atmospheric signals downstream and causes intensification of the western Pacific subtropical anticyclone (WPSA), resulting in weakened moisture supply toward East Asia from the Bay of Bengal. In addition, the remote circulation response enhances atmospheric stability over the Yangtze River valley. These two effects together cause rainfall reduction in the Yangtze River valley. Besides, the remote effect tends to offset a fraction of rainfall intensification induced by local EABC. Copyright (c) 2013 Royal Meteorological Society