Based on the daily precipitation,maximum air temperature data of 279 stations and NCEP/NCAR reanalysis data from 1979 to 2022,the standardized precipitation index for 1 month and 3 months(SPI-1,SPI-3)were calculated,the circu-lation characteristics and possible causes of the persistent high-temperature and drought events over the south of Yangtze River Valley in midsummer of 2022 were diagnosed.The results showed that:1)the rainfall was more than 50％below the historical average,the longest continuous high-temperature days reached more than 30 days in the east of Jiangxi,and most areas of Zhe-jiang broken the historical records.2)High temperature and less rainfall led to the occurrence of subsequent drought events.SPI-1 showed the extreme drought appeared over the south of Yangtze River Valley in August,while SPI-3 displayed most regions developed from normal to slight drought during July and August,particularly with moderate drought along Zhejiang coast.3)More intensive West Pacific Subtropical High and westward position of its west ridge point,the northward position of the South Asian High and its weaker moisture convergence were responsible for the high-temperature and drought events.High temperature was sustained by upward transport of surface heat,which mainly derived from a significant net surface radiation income over the south of Yangtze River Valley from July to August.4)mega-El Nino/Southern Oscillation(mega-ENSO)was the main SST variability affecting the high-temperature and drought events,which induced the anomalous anti-cyclone and cor-responding downdraft over the south of Yangtze River by triggering the out-of-phase East Asia-Pacific(EAP)teleconnection.In addition,the mega-ENSO signal appeared even earlier in the early winter,indicating that it can be used as a prediction factor for high-temperature and less rainfall events in midsummer over the south of Yangtze River valley.
high-tcmpcrature and droughtmega-ENSOsurface energy balancesouthern Yangtze River Valley
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