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Abstract:

Analysis of circulation and impact of extreme weather processes is the basis of refined disaster prevention and mitigation services. Based on meteorological observation data, reanalysis data and satellite data, the characteristics, atmospheric circulation background and its main impacts of the extreme heatwave event in the Sichuan Basin from 25 July to 9 August 2021 are analyzed. During this heatwave event, temperatures of 13 national meteorological stations broke the historical maximum temperature records, and high temperature days reached 14 days at six stations. The heatwave center was located in the central and southern parts of the Sichuan Basin, and the process intensity reached its peak in early August, and the daily maximum temperature (42.4 ℃) appeared at Xingwen station in Yibin. The analysis shows that the atmospheric circulation background of this heatwave is different from that of most previous heatwave processes, the direct role of the western Pacific subtropical high (subtropical high) during this process is not obvious, and the typhoon activity in the southeast coast prevents the westward extension of the subtropical high. The peripheral flow of the subtropical high is conducive to the maintenance of the anticyclonic system over the basin, and makes it difficult for water vapor from the south to reach the basin, which plays an important role in the development and maintenance of high temperature and heatwave. During this heatwave process, the average high temperature days in Chengdu reached 8.36 days and the heat island effect is significant. The impact of heatwave and urban heat islands effect on mega-cities like Chengdu worths attention.

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