2020年5月大气环流和天气分析

Analysis of the May 2020 Atmospheric Circulation and Weather

2020年5月主要的环流变化是北半球中高纬完成从冬季三波型向夏季四波型的转换,南海夏季风在第四候爆发。另外极涡呈单极偏心型分布,偏向北美一侧,强度略弱,西太平洋副热带高压强度较常年偏强,南支槽较常年偏弱。5月主要的天气气候特点是全国平均气温为17.2℃,较常年同期偏高1℃,为1961年以来历史同期第四高;全国平均降水量为68.5 mm,接近常年同期。月内我国共出现6次区域性暴雨天气过程;我国中东部出现1961年以来最早高温过程,多地最高气温突破当月历史极值;江淮、黄淮和云南等地出现中度到重度干旱;北方地区有2次沙尘天气过程。

The main characteristics of the general atmospheric circulation in May 2020 is that the circulation finished the transition from a three-wave pattern to a four-wave pattern in middle-high latitudes of the Northern Hemisphere,and the South China Sea summer monsoon erupted in the fourth pentad.In addition,there was one polar vortex center in the Northern Hemisphere,slightly weaker than usual.The strength of Western Pacific subtropical high was a little stronger than that in normal years,and the south branch though was a little weaker.The monthly mean temperature was 17.2℃,1.0℃higher than normal,which ranks the fourth highest since 1961.The monthly mean precipitation amount was 68.5 mm,closed to normal(69.5 mm).Six regional torrential rain processes occurred in China this month.The earliest high temperature process since 1961 occurred in the central and eastern China in May,and the highest temperature in many places exceeded the historical extreme values of the month.Severe droughts occurred in Jianghuai,Huanghuai and Yunnan,and two sand-dust weather events happened in the northern part of China.