2013年4月大气环流和天气分析

Analysis of the April 2013 Atmosphere Circulation and Weather

2013年4月大气环流特征为:北半球极涡呈绕极分布,强度接近常年;中高纬度呈4波型,东亚大槽较常年明显偏强;中低纬度地区南支槽和副热带高压强度都稍偏弱,不利于西南地区旱情的缓解。4月全国平均气温为11.0℃,与常年同期持平,东北地区气温异常偏低。全国平均降水量为43.2 mm,较常年同期偏少1.5 mm。月内我国共出现了2次冷空气过程,并伴有扬沙、浮尘甚至沙尘暴天气;南方地区共有3次大到暴雨过程,以4月29-30日过程强降雨范围最广、强度最强,其中江南、华南地区还伴随有明显的强对流活动。

The following are the main characteristics of the general circulation of atmosphere in April 2013. There is one polar vortex center in the Northern Hemisphere,and the strength is similar to normal years. The circulation presents a four-wave pattern in middle-high latitudes.Both of the south branch trough and the Northwestern Pacific subtropical high（NPSH） are slightly weaker,unfavourable for the drought relief in southwestern China.The monthly mean temperature is 11.0°C,equal to the value in the normal years except the unusual low temperature in northeast.The average precipitation of China is 43.2 mm,1.5 mm less than the normal.There are 2 cold surge processes accompanied by sand-dust events in April.The southern part of China has 3 severe precipitation events,of which the process in 29—30 April covers the largest area and has the strongest intensity,especially in South China and Jiangnan region,severe convections happen at the same time.