South China experienced a series of unprecedented extreme heat wave (EHW) events in early summer (June–July) 2020, which broke the historical record for the frequency of EHW events since 1979. Observational analyses showed that the prolonged EHW events were primarily induced by an anomalous tropospheric circulation over South China with a barotropic structure. This was attributed to the exceptional westward displacement of the western Pacific subtropical high (WPSH) and the eastward-extended upper-level South Asia high (SAH). In addition, the value of the SAH–WPSH index, which describes the relative displacement of the SAH and WPSH, also broke the historical record. Further analysis revealed that the EHW events in South China were closely associated with warming of the tropical Indian Ocean (TIO) sea surface temperature (SST), which affected both the SAH and WPSH via atmospheric teleconnections. Sensitivity and pacemaker experiments using an atmosphere-only and a coupled global climate model, respectively, suggested that the anomalous warming of the SST in the TIO directly caused the significant southeastward displacement of the intensified SAH as a result of diabatic heating in the troposphere. This heating also led to a westward-displaced WPSH via an induced mid- to lower tropospheric Kelvin wave and the associated Ekman divergence. In summary, warming in the TIO sustained exceptional shifts in both the SAH and WPSH, which favored the formation of a stationary anomalous high over South China that ultimately contributed to the record-breaking EHW events in early summer 2020.

2020年初夏（6-7月）华南地区经历了一系列前所未有的极端热浪（EHW）事件，打破了1979年以来EHW事件频率的历史记录。观测分析表明，长时间的EHW事件主要是由具有正压结构的华南异常对流层环流。这归因于西太平洋副热带高压（WPSH）和南亚高压（SAH）向东延伸的异常向西位移。此外，描述南亚高压和副高相对位移的SAH-WPSH指数的值也打破了历史记录。进一步分析表明，华南地区的 EHW 事件与热带印度洋（TIO）海表温度（SST）的变暖密切相关，它通过大气遥相关影响了 SAH 和 WPSH。分别使用仅大气和耦合全球气候模型的敏感性和起搏器实验表明，由于对流层非绝热加热，TIO中SST的异常变暖直接导致增强的SAH向东南方向显着位移。这种加热还通过诱导的对流层中下层开尔文波和相关的埃克曼散度导致了向西偏移的副副高。综上所述，TIO 变暖持续了 SAH 和 WPSH 的异常变化，这有利于华南上空形成静止异常高压，最终促成了 2020 年初夏创纪录的 EHW 事件。分别使用仅大气和耦合全球气候模型的敏感性和起搏器实验表明，由于对流层非绝热加热，TIO中SST的异常变暖直接导致增强的SAH向东南方向显着位移。这种加热还通过诱导的对流层中下层开尔文波和相关的埃克曼散度导致了向西偏移的副副高。综上所述，TIO 变暖持续了 SAH 和 WPSH 的异常变化，这有利于华南上空形成静止异常高压，最终促成了 2020 年初夏创纪录的 EHW 事件。分别使用仅大气和耦合全球气候模型的敏感性和起搏器实验表明，由于对流层非绝热加热，TIO中SST的异常变暖直接导致增强的SAH向东南方向显着位移。这种加热还通过诱导的对流层中下层开尔文波和相关的埃克曼散度导致了向西偏移的副副高。综上所述，TIO 变暖持续了 SAH 和 WPSH 的异常变化，这有利于华南上空形成静止异常高压，最终促成了 2020 年初夏创纪录的 EHW 事件。表明由于对流层非绝热加热，TIO海温异常增温直接导致增强的南亚高压向东南方向显着位移。这种加热还通过诱导的对流层中下层开尔文波和相关的埃克曼散度导致了向西偏移的副副高。综上所述，TIO 变暖持续了 SAH 和 WPSH 的异常变化，这有利于华南上空形成静止异常高压，最终促成了 2020 年初夏创纪录的 EHW 事件。表明由于对流层非绝热加热，TIO海温异常增温直接导致增强的南亚高压向东南方向显着位移。这种加热还通过诱导的对流层中下层开尔文波和相关的埃克曼散度导致了向西偏移的副副高。综上所述，TIO 变暖持续了 SAH 和 WPSH 的异常变化，这有利于华南上空形成静止异常高压，最终促成了 2020 年初夏创纪录的 EHW 事件。