The characteristics of general circulation of atmosphere in April 2012 are as follows. There is only one polar vortex center in the Northern Hemisphere, and the strength is similar to normal years. There are four waves around the earth in middle high latitudes and the strength of Ural blocking high is higher than the normal that leads to several streams of cold air to influence China. More south waves are at middle low latitudes and the East Asia major trough is stronger than usual at the same period. In April, the mean temperature is 11.7℃, 1.0℃ warmer than the same month of normal years (10.7℃). The average precipitation over China is 45.6 mm which is 2.5 mm more than climatological normal 43.1 mm. There are 8 rainstorm precipitation events and 6 sand dust events in April. Especially in South China and Jiangnan area many severe convection events with thunderstorm gale and hail happening.