2020年7月大气环流和天气分析

Analysis of the July 2020 Atmospheric Circulation and Weather

2020年7月北半球大气环流主要特征表现为:极涡分裂为多个中心呈绕极分布,较常年同期均偏强;西太平洋副热带高压较常年同期强度偏强,位置偏西偏南,副热带高压主体中上旬稳定位于长江中下游及以南地区,下旬明显西伸北抬,并南北摆动。7月全国平均降水量为125.7 mm,较历史常年同期偏多4.2%,江南北部、江淮、江汉、黄淮以及西南地区累计降水量较常年同期偏多1~2倍,而东北地区大部、华南大部等地偏少5成左右。月内有7次区域性暴雨天气过程,主要出现在长江中下游地区、黄淮以及西南地区,共有103个站日降水量达到或超过同期极值,长江中下游、淮河流域等地出现严重汛情和洪涝灾害。全国平均气温为22.1℃,较历史同期略偏高,福建南部、广东大部、海南东部等地最高气温平均值较常年同期偏高2~4℃。中下旬,江南、华南等地出现大范围持续性高温天气,福建沿海、广东沿海以及湖南南部、四川中东部等地共81个站发生极端高温事件。2020年7月是1949年以来首个没有台风生成的"空台"7月。

The main characteristics of the general atmospheric circulation in July 2020 are shown as follows.The polar vortex splits into multiple centers distributed around the polar which were stronger than normal in the Northern Hemisphere.Compared to the normal,the western Pacific subtropical high was stronger and the position of which was further west and south.The western Pacific subtropical high was located in the middle and lower reaches of the Yangtze River and south of the Yangtze River during the first and middle dekads,and obviously extended westward and northward shifting between north and south during the last dekad of this month.The monthly mean precipitation of China in July was 125.7 mm,more than the normal by 4.2%.The positive anomaly of precipitation was significantly more than 1 to 2 times in northern part of Jiangnan,Jianghuai,Jianghan,Huanghuai,and the Southwest China.However,the negative anomaly of rainfall was 50%in the Northeast China and the South China.There were seven regional torrential rain processes in this month,seen mainly in the middle and lower reaches of the Yangtze River,Huanghuai and Southwest China.The daily precipitation of 103 stations reached or exceeded the extreme values of the same period.Severe flood disaster occurred in the middle and lower reaches of the Yangtze River and the Huaihe River Basin.The monthly mean temperature of China was 22.1℃,slightly higher than the usual.The mean maximum temperature in southern Fujian,Guangdong,and eastern Hainan was 2-4℃higher than normal.During middle and last dekads,large-scale persistent high temperature weather occurred in Jiangnan and South China,where 81 stations located in the coasts of Fujian and Guangdong,southern Hunan,and central and eastern Sichuan experienced extreme high temperatures.In terms of typhoon,it was the first time that there was no typhoon event in July 2020,which is the first time since 1949,so it is called"typhoon absence".