The relationship between extreme dragon-boat precipitation and atmos-pheric 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 precipita-tion 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 Chi-na 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 Philip-pines.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 Nina 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 sig-nificant increase in dragon-boat precipitation in South China.
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