Analysis of the April 2020 Atmospheric Circulation and Weather
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.