2022年江西省夏秋季高温干旱特征和环流形势分析

Characteristics of the Summer and Autumn High Temperature and Drought and Circulation in Jiangxi Province in 2022

【目的】为提升江西省夏秋季异常高温干旱预报能力。【方法】利用CIMISS数据中心实际观测资料、NCEP/NCAR再分析资料等,结合气象干旱综合指数(MCI),对江西省2022年夏秋干旱期间的大气环流特征进行分析。【结果】此次高温干旱过程为1961年以来所罕见,高温与干旱均具有时间长、范围广、强度大等特征,两者的叠加与协同,刷新多项气候值纪录。【结论】其大气环流形势具有以下特征:夏季槽脊稳定,副高异常偏强、偏北,孟加拉湾水汽在南海转向,并入东亚副热带夏季风,进入更北方地区,使得干旱发生发展;秋季贝加尔湖附近为弱的负高度距平,中高纬环流平直,经向环流弱于常年同期,冷空气不频繁,少于常年同期;盘踞在华南及江南部分地区分裂的副高系统偏强,阻止冷暖空气在上空交汇,上空气流的下沉造成增温和变干,低层受大陆反气旋环流、南海和西北太平洋气旋性环流影响,造成水汽输送减少,不利于降水的产生,使得干旱继续加剧。此外,7—10月无台风影响,也是江西异常高温干旱的成因之一。

By using the observation data from the CIMISS data center and the NCEP/NCAR reanalysis data,combined with the meteorological drought index(MCI),this article analyzes the characteristics of atmospheric circulation during the 2022 summer-autumn drought in Jiangxi Province for the purpose of improving the capability of predicting abnormally high temperature and drought in summer and autumn in Jiangxi Province,The results show that this high-temperature and drought process is very rare since 1961,during which both high temperature and drought had the characteristics of long duration,wide range,and high intensity.The superposition and synergy of the two have refreshed multiple climate value records.The atmospheric circulation has the following characteristics:the trough ridge was stable in summer,and the subtropical high was abnormally stronger and by north.At the same time,the water vapor in the Bay of Bengal turned direction in the South China Sea,merged with the East Asian subtropical summer monsoon,and moved northward further,causing drought to occur and develop.In autumn,there was a weak negative height anomaly near the Lake Baikal,the circulation in mid-high latitudes was flat and straight,the meridional circulation was weaker than normal,and the cold air activity was not so frequent as in normal years.Meanwhile,the subtropical high system that split in parts of South China and Jiangnan was stronger,preventing the intersection of cold and warm air in the upper air.The sinking of the upper airflow led to the warming and drying.The lower layer was affected by the circulation of the continental anticyclone,the cyclonic circulation of the South China Sea and the northwest Pacific,resulting in reduced water vapor transport,which was not conducive to precipitation,causing drought to continue and get intensified.In addition,the absence of typhoons from July to October was also one of the causes for the unusually high temperature and drought in Jiangxi.