Decomposition of projected summer rainfall change over East Asia based on timeslice experiments

The summer rainfall change over East Asia in response to CO2 forcing and the associated processes are investigated via a set of pilot timeslice piSST experiments from the Cloud Feedback Model Intercomparison Project Phase 3 (CFMIP-3). The total response of rainfall to 4 × CO2 in coupled models is decomposed into components associated with uniform SST warming, SST pattern change, the direct radiative effect of increased CO2, and the plant physiological response. In general, the contributions of the individual responses of summer rainfall to different forcings are subject to a regional dependence. The uniform SST warming reduces rainfall in many land regions in East Asia, but increases rainfall over the northern East Asia. The spatial patterns of the rainfall change as the result of SST pattern change are nearly opposite to those of the uniform SST warming, which account for most inter-model uncertainty in the simulations. The direct radiative effect of increasing CO2 is largely responsible for an increase of rainfall across the East Asian continent, especially over the central China and southern Tibetan Plateau, and the plant physiological effect appears to increase rainfall over the eastern and southern China. Also discussed are the atmospheric circulation changes that are driven by the distinct aspects of CO2 forcing and directly tied to the summer rainfall changes.