Summer Extreme High Temperature in the Bohai Rim Region and Its Relationship with Abnormal Characteristics of Atmospheric Circulation

Xu Weiping; Xing Yamin; Meng Xiangxin; Tang Zidong; Bo Zhongkai; Wang Na; Chen Ya'nan

doi:10.16765/j.cnki.1673-7148.2025.05.010

Abstract：Based on daily maximum and minimum temperature data of 753 national stations in north-ern China from 1961 to 2022 and the ERA5 monthly reanalysis data,this paper comparatively analyzes the spatial and temporal distribution characteristics of the summer warm day,warm night and compound extreme high temperature events in the Bohai Rim region and their corresponding atmospheric circulations in the same period and the previous period.The results show that,in the Bohai Rim region in summer,warm day shows a decreasing trend,while the warm night and compound extreme high temperature events show an increasing trend.Moreover,the increase in compound extreme high temperature becomes more significant.Both of the warm night and compound extreme high temperature have obvious inter-decadal variation characteristics.Warm day,warm night and compound extreme high temperature appear mainly in the early to middle of June,late June to mid-August,and mid-to-late July,respectively.In particular,the intensities of compound extreme high temperature events have increased significantly.Through the cor-responding circulation field of the three extreme high temperature index regression,it is found that the compound extreme high temperature has an obvious wave-train structure in Eurasia,similar to the result of warm day regression.But what is different is that the positive anomaly center in western Europe and the Baikal Lake region is much stronger,and the negative anomaly center in West Siberia is much wea-ker.The regression of the previous circulation fields suggests that the three extreme high temperature in-dices all have obvious wave-train structures in the mid-high latitudes.In the middle and upper tropo-sphere,a positive anomaly center of height field appears near the Baikal Lake area,accompanied by an abnormal anticyclonic circulation and the abnormal sinking motion.This is responsible for the occurrence of extreme high temperature events around the Bohai Rim region.