2020年12月大气环流和天气分析

Analysis of the December 2020 Atmospheric Circulation and Weather

2020年12月大气环流的主要特征是:北半球极涡呈偶极分布,环流呈三波型,欧亚中高纬度环流经向度大,东亚大槽偏强,南支槽偏弱。12月,全国平均降水量为5.8 mm,比常年同期(10.5 mm)偏少45.3%,全国平均气温为-3.9℃,比常年同期(-3.2℃)偏低0.7℃。月内共出现2次强冷空气过程、2次大范围降水过程和2次大范围雾-霾天气过程。其中27—31日,我国大部分地区遭遇寒潮天气,降温幅度大,影响范围广,多地最低气温突破历史极值。

The main characteristics of the general atmospheric circulation in December 2020 are as follows.Polar vortex in the Northern Hemisphere had a dipole distribution,the circulation presented a three-wave pattern in middle-high latitudes.The atmospheric circulation presented a great meridionality in mid-latitudes in Eurasia.The East Asian trough behaved strongly and the southern branch trough was weaker in this month.The monthly mean precipitation over China was 5.8 mm,45.3%less than normal(10.5 mm).The national monthly average temperature was-3.9℃,0.7℃lower than the normal.Totally,there were two strong cold air processes,two precipitation processes and two large-scale fog-haze events in this month.During 27-31 December,most of China suffered from the cold surge characterized by a sharply drop in temperatures and extremely wide areas being impacted.The lowest temperature in many places exceeded the historical extreme values.