2024年5月大气环流和天气分析

Analysis of the May 2024 Atmospheric Circulation and Weather

2024年5月北半球极涡偏单极型分布,强度偏强;中高纬完成了从冬季三波型向夏季四波型的转换,环流呈四波型,欧亚环流经向度较大,副热带高压较常年同期偏强、偏西、偏北,南支槽较常年同期偏弱。全国平均气温为17.7℃,较常年同期偏高1.2℃。全国平均降水量为69.5 mm,较常年同期偏少1%。月内,共发生5次区域性暴雨天气过程,南海夏季风于5月第6候(5月26日)爆发,较常年(5月第4候)偏晚2候。此外,发生3次强对流过程且局地遭遇风雹灾害,北方地区出现2次沙尘过程。

The main characteristics of the general circulation in May 2024 are that the polar vortex in the Northern Hemisphere was partially mono-polar with stronger intensity than usual.The 500 hPa geopotential height presented the distribution of a four-wave pattern in middle-high latitudes of the Northern Hemisphere,which means that the circulation had transformed from a three-wave pattern in winter into a four-wave pattern in summer,and the meridional degree of the Eurasian circulation was relatively high.The western Pacific subtropical high was stronger and located more westerly and northerly than that in normal years,while the south branch trough was weaker than usual.The monthly mean temperature across China in May was 17.7℃,1.2℃warmer than normal.The monthly mean precipitation was 69.5 mm,which is 1%less than normal.During this month,five regional torrential rain processes occurred in China,but the South China Sea summer monsoon erupted in the sixth pentad(May 26),2 pentads later than the normal onset time in the fourth pentad in May.In addition,three severe convection weather events occurred this month,making the hit areas suffer from gales and hailstorm.Moreover,the northern part of China was troubled by two sand-dust events in this month.