2022年夏季中国高温环流特征及其与热带海面温度异常的关系

Characteristics of High Temperature Circulation in China of the Summer 2022 and Their Relationship with Tropical Sea Surface Temperature Anomalies

基于1979~2022年NCEP/DOE逐月再分析资料和NOAA海面温度资料,通过合成、相关分析等统计方法,以海面温度(Sea Surface Temperature,SST)异常影响为切入点,对比分析了2022年与La Niña年强迫作用下的我国夏季季节内环流差异,并在此基础上进一步探讨了异常高温与同期热带SST之间存在的可能联系。结果表明:1)2022年夏季,我国中东部高温区具有明显空间变化特征,6月位于华中地区、7月位于西南地区、8月影响整个长江流域。2)西太平洋副热带高压和南亚高压的同时异常加强,以及两者重叠打通并形成少见的北半球副热带高压带,是造成2022年夏季我国中东部异常高温过程的直接原因。3)在持续2年的较强La Niña背景下,2022年东亚夏季环流并未完全表现出对La Niña冷SST的响应,南海及菲律宾以东对流异常偏弱、东亚—太平洋遥相关型不显著均与La Niña年环流典型特征有较大出入。夏季同期热带SST异常对高温过程的形成具有一定贡献,热带西印度洋和热带中太平洋的冷SST异常分别有利于我国长江流域和华中地区出现高温酷暑,其中热带中太平洋冷SST异常可能是西太平洋副热带高压加强的重要原因,而热带西印度洋冷SST对南亚高压的增强有贡献作用。

Intraseasonal circulation characteristics in the summer of 2022 and the influences from tropical oceans were studied by using the NCEP/DOE monthly reanalysis data and NOAA observational datasets during 1979–2022 with the composite and correlation analysis methods.The results show that there are significant spatial variations in temperatures in Central and Eastern China,the center of high temperature anomalies located in Central China,Southwest China,and the entire Yangtze River Basin in June,July,and August,respectively.The simultaneously strengthened Western Pacific Subtropical High(WPSH)and South Asian High(SAH),as well as their overlap,ultimately formed a rare Northern Hemisphere subtropical high,which is the direct cause of the high temperature in Central and Eastern China in the summer of 2022.However,the East Asian summer circulation in 2022 is distinct from a classic response to La Niña.The weak convection anomalies in the South China Sea and east of the Philippines and the insignificant East Asia-Pacific teleconnection pattern are both different from the typical La Niña years.The tropical Sea Surface Temperature(SST)anomalies in the summer of 2022 contributed to the formation of these extreme high temperature processes.The cold SST anomalies in the tropical West Indian Ocean and tropical Central Pacific Ocean are conducive to the occurrence of high temperatures in the Yangtze River Basin and Central China,respectively.The cold SST anomalies in the tropical West Indian Ocean contribute to the strengthening of the SAH,whereas the cold SST anomalies in the tropical Central Pacific Ocean may be an important cause of the strengthened WPSH.