Influence of developing phase of the El Niño events on the summer extreme precipitation in eastern China

Using the reanalysis data and precipitation dataset during 1961-2020, this paper analyzes the influence of developing phase of the Eastern Pacific El Niño events on the summer extreme precipitation in China. Results are shown as follows. During the developing summer, El Niño mainly affected Eastern China, resulting in the extreme precipitation in North China and Jiangnan region decreased, while the extreme precipitation in Jianghuai region increased significantly. The physical process is further analyzed. When the Eastern Pacific El Niño event is in the developing summer, significant positive SST anomalies were observed in the equatorial Eastern Pacific and negative SST anomalies were observed in the Western Pacific, which are associated with anticyclonic circulation anomalies. There were positive SST anomalies in the Northwest Pacific, corresponding to the cyclonic circulation anomalies. The anomalous SST stimulated the “+ - +” EAP wave train anomalies and caused “- + -” precipitation configuration. At the intersection of anomalous circulations, it showed a significant anomalous convergence and ascent, which brought sufficient water vapor to the Jianghuai region. However, North China was mainly controlled by anticyclonic circulation and Mongolian high, and was affected by the anomalous northwest wind from the high latitudes. There was a significant anomalous divergence and sinking, the dynamic conditions of precipitation were insufficient. In addition, during the developing phase of the Eastern Pacific El Niño events, the Western Pacific subtropical high shifted eastward, which weakened the occurrence of precipitation and water vapor transport in Jiangnan region, resulting in the extreme precipitation in Jiangnan region decreased. The above results highlight the important impact of the Eastern Pacific El Niño events on extreme precipitation in China during the developing summer, and provide a theoretical basis for regional extreme climate prediction.