Effects of anthropogenic emissions of CO₂ and aerosols on decadal transition of summer precipitation over eastern China in the late 1970s

In the background of global warming, summer precipitation over eastern China (ECSP) experienced a significant decadal change at the end of the 1970s with positive rainfall anomalies over northeastern China and the middle and lower reaches of the Yangtze River and negative rainfall anomalies over northern and southern China. We examined anthropogenic emissions of CO₂ and aerosols which had discernible decadal transitions around the mid to late 1970s and contributed to the ECSP change, and elucidated the underlying mechanism. Moisture budget over eastern China was calculated using the Community Earth System Model (CESM). The water vapor convergence over the Yangtze-Huai River valley and moisture divergence over southern China in the CO₂ simulation are dominated by the combined effects of the dynamic contribution related to mass divergence and the thermodynamic contribution related to moisture gradients, which have greater effect on the ECSP than that of aerosols. Aerosols forcing contributed to the rainfall increase over the Yangtze-Huai River valley and decrease over southern China primarily by the dynamic effect. The enhanced upward and downward motions caused by changes in temperature gradient led to similar rainfall anomalies over eastern China under the effects of CO₂ and aerosols, although their impacts on radiation and temperature were different. These results confirm that CO₂ and aerosols did have some effect on the decadal transition of ECSP at the end of the 1970s.