Modeling Study of Aerosol Indirect Effects on Climate with an AGCM-aerosol Coupled System

摘要

Aerosol indirect effects (AIEs) on global climate are quantitatively investigated by introducing aerosol–cloud interaction parameterizations for stratus clouds into an AGCM (BCC_AGCM2.0.1) developed by the National Climate Center of the China Meteorological Administration coupling with the Canadian Aerosol Module (CAM). The study yields a global annual mean of –1.57 W m-2 for the first indirect radiative forcing. The second indirect effect leads to global annual mean changes in net shortwave flux of –0.58 W m-2 at the top of the atmosphere (TOA). The total AIE reduces the global annual means of net shortwave flux at the TOA and of surface temperature by 2.27 W m-2 and 0.12 K, respectively. Change in surface temperature induced by the total AIE is clearly larger in the Northern Hemisphere (–0.21 K) than in the Southern Hemisphere, where changes are negligible. The interhemispheric asymmetry in surface cooling results in significant differences in changes of the interhemispheric annual mean precipitation rate, which could lead to a tendency for the ITCZ to weaken and broaden. In summer, the northeasterly or northerly flows in most areas of east and south China and over the nearby oceans are enhanced due to the total AIE, which weakens the transport of warm and moist air carried by the East Asian summer monsoon, and decreases the summer monsoon precipitation in east and south China.