Interdecadal change on the relationship between the mid-summer temperature in South China and atmospheric circulation and sea surface temperature

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South China suffers from high temperature frequently in mid-summer and this study aims to explore the interdecadal change of interannual variation of the mid-summer temperature in South China. It is revealed that the relationship between South China temperature and atmospheric circulation and sea surface temperature anomaly (SSTA) experiences an interdecadal change around the early 1990s. Before the early 1990s, warmer summer in South China is associated with the mid-latitude teleconnection featured by higher pressure over the Ural Mountains and the Korean Peninsula and lower pressure around the Lake Baikal. South China is located at the southern flank of an anomalous high pressure. After the early 1990s, South China temperature is prominently influenced by the tropical SSTA, and meanwhile the mid-latitude teleconnection becomes much weaker. Warmer summer is associated with higher pressure centered over South China and the El Nino to La Nina transition phase. The higher pressure influencing South China is located more southwards after the early 1990s, and it is favored by the tropical SSTA. The warmer SST in summer over the western tropical Pacific enhances the local convection and triggers an anomalous local Hadley cell with stronger subsidence over South China, directly leading to higher pressure over South China. Moreover, the colder SST over the central–eastern Pacific induces an anomalous Walker circulation and further strengthens the convection over the western tropical Pacific, exerting an indirect impact on the higher pressure over South China. The relative role of the western Pacific warming and central–eastern Pacific cooling is verified by CAM4 simulations. The intimate relationship between the tropical SSTA and South China temperature occurs during the El Nino to La Nina transition phase, which is the case after the early 1990s and suggests higher predictability for South China temperature in the recent decades.