Abstract:

The continuous high temperature is affecting China’s environment, economy and social production in varying degrees. Based on the daily precipitation and maximum temperature data of 234 meteorological stations in the middle reaches of the Yangtze River from 1971 to 2022, the reanalysis data from National Centers for Environmental Prediction/National Center for Atmospheric Research and sea surface temperature (SST) data from National Oceanic andAtmospheric Administration, the characteristics of atmospheric circulation in summer high temperature anomaly years and its relationship with SST are analyzed. The results are as follows: The summer high temperature days in the middle reaches of the Yangtze River presented a significantly increasing trend in the past 52 years, especially since the beginning of the 21st century. The annual average number of high temperature days in summer in the middle reaches of the Yangtze River was 19 days. In 2022, the number of high temperature days in summer was the most (74 days), compared with the average climate state in the past 30 years, the anomaly percentage is 163 % higher, and in 1987 it was only 5 days. Under the influence of the teleconnection wave train of the subpolar waveguide, the East Asian continental high pressure is enhanced, and the anticyclonic circulation controls the middle reaches of the Yangtze River. At the same time, the position of the East Asian summer westerly jet is northward, which promotes the west Pacific subtropical high to extend westward and northward. The strong sinking motion suppresses the development of low-level convection, and the radiation warming effect is obvious. As a result, the high temperature days in summer in the middle reaches of the Yangtze River are abnormally more. The high temperature days in summer in the middle reaches of the Yangtze River are positively correlated with SST (especially in summer) of the equatorial northern Indian Ocean, the North Atlantic and the mid-low latitude western Pacific. Beside, the summer high temperature days are negatively correlated with SST of the equatorial central and eastern Pacific. From the beginning of the previous winter, the SST of the equatorial northern Indian Ocean and the North Atlantic continues to be high, and the SST of the western Pacific in the middle and low latitudes gradually begins to increase. At the same time, the equatorial central and eastern Pacific is in an abnormal La Nina state in summer, which is conducive to abnormally more high temperature days in the middle reaches of the Yangtze River.

Key words: high temperature days, the middle reaches of the Yangtze River, atmospheric circulation, sea surface temperature anomaly

摘要：

全球变暖加剧了气候系统的不稳定性和极端天气的频发，“热岛效应”和高温热浪的叠加，给人们的生命安全和经济生产造成巨大损失，本文利用1971—2022年长江中游234个站点日降水量和最高气温数据、美国国家环境预报中心/国家大气研究中心（National Centers for Environmental Prediction/National Center for Atmospheric Research，NCEP/NCAR）再分析资料和美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration， NOAA）海表温度（简称“海温”）资料，分析夏季高温异常年的大气环流特征及其与海温的关系。结果表明：近52 a来尤其是进入21世纪，长江中游夏季高温日呈显著增加趋势，年均高温日为19 d。其中，2022年高温日数最多达74 d，与近30 a气候态平均相比，距平百分率高出163%，1987年高温日最少仅5 d。夏季高温日偏多年，在副极地波导的遥相关波列影响下，东亚大陆高压增强，反气旋性环流控制长江中游地区，同时东亚夏季西风急流位置偏北，促使西太平洋副热带高压西伸北抬，强烈的下沉运动抑制低层对流发展，辐射增温作用明显。高温日数与赤道北印度洋、北大西洋和中低纬西太平洋海温，尤其是夏季海温呈正相关关系，与赤道中东太平洋海温呈负相关。从前冬开始赤道北印度洋和北大西洋海温持续偏高，中低纬西太平洋海温逐渐开始升高，同时夏季赤道中东太平洋呈异常La Ni?a状态，有利于长江中游夏季高温日异常偏多。

关键词: 高温日数, 长江中游, 大气环流, 海温异常