Analysis of the March 2011 Atmospheric Circulation and Weather

The following are the main characteristics of the general atmospheric circulation in March 2011. There is a strong polar vortex centre in the Northern Hemisphere.The circulation presents a four-wave pattern in middle-high latitudes.The south branch trough is slightly stronger than the normal,and the Northwestern Pacific subtropical high(NPSH) is slightly weaker.The regional averaged precipitation for whole China is 20.4 mm,and 27%less than the normal,which is the least in the past ten years.There are 7 main precipitation processes,which mainly occurred in the second and the last dekad,induced by cold surge,south branch trough,and NPSH.The monthly mean temperature is 2.4℃,and 0.8℃lower than the normal,which is the lowest in the past 23 years.There are two cold surge processes affecting most areas of China,which result in the disasters,such as snow storm and sand slides in east of Gansu and east of Tibet,northwest of Yunnan,and west of Sichuan.