2022年华南极端“龙舟水”与大气环流及海温异常的关系

利用华南192个国家气象观测站逐日降水资料,NCEP/NCAR大气环流再分析资料,NOAA月平均海表温度资料(ERSST V5)及向外长波辐射(OLR)资料,采用相关、合成分析的方法研究了2022年华南“龙舟水”异常与大气环流及海温异常的关系。结果表明,2022年“龙舟水”期间,东亚大槽、东北冷涡偏强,南下冷空气偏强,同时西太平洋副热带高压和南支槽均偏强,在华南存在明显的水汽辐合。2022年发生的拉尼娜事件,大气环流对其有明显响应,Walker环流增强,华南对流明显加强,菲律宾以东存在异常反气旋环流,副高加强导致其西北侧的西南风加强,向华南水汽输送显著增强,同时华南存在显著的上升运动。大气环流和海温的异常导致2022年华南极端“龙舟水”。

The relationship between extreme dragon-boat precipitation and atmospheric circulation and SST anomaly in South China in 2022

During the dragon-boat precipitation period in 2022 (from May 21 to June 21),the average precipitation in South China was 472.5 mm,the second largest in history,the third largest in Guangdong and the largest in Guangxi since meteorological records began in 1951.This event led to river basin flooding in the Pearl River basin and catastrophic floods in the Beijiang River basin.Using daily precipitation data from 192 national meteorological observation stations in South China,NCEP/NCAR atmospheric circulation data,atmospheric outward long-wave radiation (OLR) data,and NOAA monthly-scale SST reanalysis data,we studied the characteristics of South China Dragon-boat precipitation anomaly in 2022 and its relationship with atmospheric circulation and sea surface temperature using correlation and composite analysis methods.The results indicate a significant strengthening of the East Asian trough and the northeast cold vortex,intensifying the cold air influence over South China.The southern branch trough also intensified,accompanied by an abnormal anticyclonic circulation east of the Philippines.The subtropical high strengthened,facilitating the transport of warm and humid air from the tropical Western Pacific and South Sea to South China via the southernly monsoon airflow.Additionally,the southwest monsoon warm and humid airflow persisted in South,supported by a strengthening blocking high pressure in the Okhotsk Sea.Ground sea-level pressure exhibited an abnormal distribution,with high pressure in the north and low pressure in the south across high to medium-low latitudes in the Northern Hemisphere.The significant upward movement in South China,coupled with evident water vapor convergence,resulted in extreme dragon-boat precipitation in South China in 2022.Furthermore,the La Niña event in the equatorial central eastern Pacific in 2022 significantly influenced atmospheric conditions,enhancing the Walker circulation.This suppressed convective activity east of the Philippines during the dragon-boat precipitation period,stimulating abnormal anticyclonic circulation and the appearance of Rossby waves in the atmosphere east of the Philippines.The abnormal southerly airflow from the South China Sea to South China facilitated the transport of warm and humid water vapor,contributing to the significant increase in dragon-boat precipitation in South China.