Dipole response of early‐summer rainfall in eastern China to 1.5 and 2.0°C global warming

Abstract

AbstractThe 2015 Paris Agreement set the goal of pursuing efforts to keep global warming to 1.5°C above the pre‐industrial level. It remains unclear how the early‐summer rainfall in China responds to moderate warming. Here, we investigate the changes in June rainfall in eastern China by 1.5 and 2.0°C warming using the ensemble projection from Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) dataset. Results reveal a dipole response in the June rainfall with the significant increase in southeastern China but a slight decrease in northeastern China at 1.5 and 2.0°C warming compared to the present day. The moisture budget analysis indicates that the dipole rainfall response is caused predominantly by the dynamic response in the anomalous circulation and in turn moisture transport. Compared to the present day, the upper‐tropospheric temperature is significantly enhanced in the tropics but decreased in middle latitudes at the 1.5 and 2.0°C warming. The enhanced poleward temperature gradient strengthens zonal wind on the south of the East Asian westerly jet, leading to a southward displacement of jet. As a result, an anomalous upward motion is reinforced over the north of 30°N with an anomalous downward motion over the south of 30°N, leading to a dipole rainfall anomaly in eastern China. In addition, the warming also induces a thermodynamic response with increased moisture and in turn rainfall across eastern China, further enhancing rainfall in southeastern China, but weakening the decreased rainfall in northeastern China.