2023年7月广西持续性高温天气成因及前兆信号分析

Analysis of causes and precursor signals of persistent heat waves in Guangxi in July 2023

利用广西91个国家气象观测站最高气温逐日资料和NCEP/NCAR再分析资料、NOAA向外长波辐射资料,国家气候中心130项气候系统监测指数资料,分析2023年7月广西持续性高温天气的成因,探寻其前兆信号。结果表明,7月9-16日和22-29日,广西出现2次大范围高温天气过程,全区平均高温日数12 d,为1951年以来同期第3多。两个高温天气过程中,广西受台风西侧外围下沉气流控制,副热带高压强度偏强,位置偏北偏西、南亚高压异常东扩。深厚高压系统控制下的异常下沉增温作用导致广西2023年7月高温天气的发生发展。前期3-4月热带西太平洋暖池海温特征量与当年7月广西高温日数呈显著正相关,此因子可作为7月广西高温天气一个可靠的前兆信号。

Based on the daily maximum temperature from 91 weather stations in Guangxi and reanalysis data from NCEP/NCAR,outgoing longwave radiation data from NOAA,and 130 circulation indexes from National Climate Center in China,the causes of high temperature weather process in Guangxi in July 2023 were analyzed,and their precursor signals were explored.The results showed that there were two widespread high-temperature weather processes in Guangxi during 9—16 and 22—29 July,2023 in Guangxi.The average number of high-temperature days in Guangxi was 12,which is the 3rd greatest during the same period since 1951.Guangxi was controlled by the western peripheral sinking air flow of tropical cyclones.During the two processes,the western Pacific subtropical high was strong,with its position expanding north-westerly,and the South Asian High also has shown an abnormally eastward extension.The effect of anomalous subsidence and warming controlled by the deep high-pressure system leaded to the development of persistent heat waves in Guangxi in July 2023.The warm pool SST index in the tropical western Pacific Ocean in March-April is significantly positively correlated with the number of high temperature days in Guangxi in July,which can be used as a reliable preceding signal of persistent heat waves in July in Guangxi.