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2022年夏季重庆极端高温天气特征及其成因分析

Analysis of characteristics and causes of extreme high temperature Analysis of characteristics and causes of extreme high temperature

  • 摘要: 2022年夏季,重庆出现两次极端高温天气过程。利用重庆地区34个气象站点观测资料和ERA5再分析资料,分析了两次高温过程的主要环流异常特征。结果表明:南亚高压加强东伸和西太平洋副热带高压(以下简称副高)异常加强及西伸北抬,日本海以北至鄂霍次克海地区异常强盛的阻塞高压(以下简称鄂海阻高),使北方冷空气盘踞在40°—50°N以北地区,难以南下影响包括重庆在内的长江流域,重庆处于副高西段异常强盛的下沉和水汽辐散中心区,造成该地区持续极端高温天气。分析2001年以来不同等级区域性高温天气过程中的副高和南亚高压指数发现,2022年夏季副高西伸至最西,同时南亚高亚中心异常偏东,二者直接造成了重庆的极端高温天气。并且2022年夏季赤道太平洋西部海温的异常偏暖,130°E—150°W、30°—60°N区域平均距平值为1961年以来同期最高值,促使鄂海阻高强盛。在La-Niña事件作用下,110°—120°E范围内Hadley环流在20°—30°N为强盛的下沉运动,其下沉支与副高中心下沉区叠加,造成副高异常偏强和西伸,进而引发重庆极端高温天气。

     

    Abstract: During the summer of 2022, two periods of extreme high temperature events occurred in Chongqing. Using observations from 34 sites in the Chongqing and ERA5 reanalysis data, the main circulation anomalies during this period were analyzed. The results indicate that the strengthening and eastward extension of the South Asian High, along with the abnormal intensification and westward-northward extension of the Western Pacific Subtropical High (hereafter referred to as the Subtropical High), and the occurrence of an anomalously strong blocking high pressure north of the Sea of Japan extending to the Sea of Okhotsk (hereinafter referred to as the Okhotsk Blocking High), resulted in the stagnation of cold air above the 40°—50°N region, rendering it unable to influence the Yangtze River basin, including Chongqing. Chongqing was situated in a region of abnormally intense subsidence and moisture divergence under the western section of the Subtropical High, leading to persistent extreme high temperatures in the area. Analysis of the Subtropical High and South Asian High indices for different levels of regional high-temperature events since 2001 revealed that the Subtropical High extending westward to its most extreme position, while the center of the South Asian High was anomalously eastward in the summer of 2022. These factors directly contributed to Chongqing's extreme high temperatures. Additionally, the summer of 2022 witnessed anomalously warm sea surface temperatures in the western equatorial Pacific, with the average anomaly value in the 130°E—150°W, 30°—60°N region being the highest since 1961 for the same period, which strengthened the Okhotsk Blocking High. Under the influence of the La Niña event, Hadley circulation within the 110°—120°E range featured strong subsidence movements at 20°—30°N. This subsidence, combined with the central subsidence area of the Subtropical High, led to the abnormal intensification and westward extension of the Subtropical High, which in turn triggered the extreme high temperatures in Chongqing.

     

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