Season division and its temporal and spatial variation features of General atmospheric circulation in East Asia

Using the NCEP-DOE Reanalysis 2 data of air temperature, geopotential height, relative humidity and wind field of 17 pressure levels from 1979 to 2009, and the Multi-factor Fisher optimal dissection method, the seasons of the general atmospheric circulation in East Asia are diuided. The main results are as follows. (1)The seasonal establishment of atmospheric general circulation is initiated from subtropic of the stratosphere in East Asia. In the troposphere the spring and the summer first start from the tropical regions, and then extend into middle latitudes. The autumn and the winter first start from middle latitudes, and then extend into low latitudes. (2) In the troposphere the seasonal establishment of atmospheric general circulation is more consistent, and it is very different from that in the stratosphere. And the seasonal establishments of the middle and the low level of the stratosphere are not very consistent. (3)In the past 30 years, the four seasons have started much earlier in about 6 years, in which years some stronger El Nio phenomena just happened. That implies that the El Nio phenomenon causes abnormal seasonal variation.