2023年4月大气环流和天气分析

Analysis of the April 2023 Atmospheric Circulation and Weather

2023年4月北半球极涡强度偏强且呈偶极型分布;中高纬环流呈异常四波型,亚洲环流较平直。我国北方基本为500 hPa高度场负距平,副热带高压较常年偏弱,南支槽较常年偏西偏弱。全国平均气温为11.4℃,较常年同期偏低0.1℃。全国平均降水量为48.7 mm,较常年同期(43.6 mm)偏多11.7%,其中西北和华北地区降水较常年同期显著偏多。月内冷空气过程频繁,出现4次冷空气过程,降温幅度大;全国范围内共发生4次大范围暴雨过程,6次区域性强对流过程,局地强度强。此外,北方地区出现6次沙尘天气过程,云南等地干旱持续发展。

The main characteristics of the general atmospheric circulation at 500 hPa in April 2023 are as follows.There were two polar vortex centers in the Northern Hemisphere,stronger than usual.The circulation in middle-high latitudes showed an anomalous four-wave pattern,and the Asian circulation was relatively flat and straight.The northern part of China had a negative anomaly in the geopotential height field,the strength of western Pacific subtropical high was weaker than that in normal years,and the south branch was a little weaker,more westward than usual.The monthly mean temperature was 11.4℃,0.1℃lower than normal.The monthly mean precipitation was 48.7 mm,11.7%more than the value(43.6 mm)in normal periods,of which the precipitation in the Northwest China and North China was significantly more than that in normal years.In addition,cold air was very active during this month,and four cold air processes occurred,bringing large amplitude of drop in temperature.There were four large-scale torrential rain processes across China and six regional severe convection processes with strong local intensities.In addition,six sand-dust events occurred in northern China,and drought maintained and developed in Yunnan and other places.