2020年4月大气环流和天气分析

Analysis of the April 2020 Atmospheric Circulation and Weather

2020年4月大气环流呈单极型分布,中高纬环流为三波型,西太平洋副热带高压强度与常年相当,南支槽较常年偏弱。4月全国平均气温为11.2℃,接近常年同期,全国共有18个站日降温幅度达到极端事件标准。全国降水量为33.7 mm,较常年同期(45.1 mm)偏少25.3%。月内共出现2次主要冷空气过程,4次大范围降雨过程;云南气象干旱缓解,长江以北多地气象干旱发展;北方地区出现1次沙尘暴天气,较常年同期明显偏少。

The main characteristics of the general atmospheric circulation in April 2020 are as follows.There was one polar vortex center in the Northern Hemisphere,the 500 hPa geopotential height presented the distribution of a three-wave pattern in the high latitude of Northern Hemisphere.The strength of Western Pacific subtropical high was closed to that in normal years,but the south branch though was a little weaker.The monthly mean temperature was 11.2℃,closed to normal,and a total of 18 stations across the country measured the sharp drop in temperature,which reached the standard of extreme events.The monthly mean precipitation amount was 33.7 mm,25.3%less than in normal period(45.1 mm).Two cold air processes and four rainfall processes occurred in China this month.The meteorological drought condition in Yunnan Province got alleviated,but continued in many areas north of the Yangtze River.Only one sand-dust event happened in the northern part of China,significantly less than in normal period.