Abstract:The following are the main characteristics of the general circulation of atmosphere in September 2011. The polar center over the Northern Hemisphere is a single vortex pattern and deviated to the Western Hemisphere. The circulation presents a five wave pattern in middle high latitudes and the trough areas are over the northeast part of North Pacific, the east part of North America, the north part of North Atlantic, the east part of Europe and the northeast part of Asia, respectively. A negative anomaly with more than 160 gpm difference is found over the northeast part of North Pacific on the 500 hPa geopotential height field. The intensity of the subtropical high over the Northwest Pacific is weaker than the corresponding period of normal years. The location of west ridge spot is further east and north than normal years. The monthly mean temperature (16.4℃) is 0.4℃ higher than the same period of normal years and the mean precipitation (65.0 mm) is nearly the same as the value (65.3 mm) of normal years. In this month, there were 3 obvious cold air processes and 7 precipitation processes, 7 tropical cyclones generated, in which typhoon Nesat landed in China and resulted in heavy damages.