The Interdecadal Variation of Winter Temperature in China and Its Relation to the Anomalies in Atmospheric General Circulation

By using the monthly temperature in 160 stations of China and the NCEP/NCAR reanalysis data,the winter(November to March) temperature variations from 1951 to 2000 are studied with the empirical orthogonal function(EOF) analysis.The first EOF has an identical signal in whole China and demonstrates that the winter temperature has increased since the middle of 1970s in China.The second EOF has a seesaw pattern between southern and northern China and shows a warming in the 1980s and 1990s in Northwest China and Northeast China.The interdecadal variation with periods longer than 8 years can also be revealed using Fourier harmonics analysis.In addition,the warming superimposition of EOF1 and EOF2 probably causes persistent warming winter in China from the 1980s.This significant warming may intensify the drought in North China,since there are no obvious changes in the regional precipitation.The linear regressions of the atmospheric general circulation upon the winter temperature on interdecadal time scales indicate that the first EOF of temperature is significantly correlated to the Arctic Oscillation(AO),with a quasi-barotropic annular mode in the geopotential height field.However,the second EOF of temperature is closely associated with height anomalies of wavenumber one in middle-high latitudes,with a quasi-barotropic out-of-phase oscillation between the Pacific Ocean and the Atlantic Ocean.The results show that the interdecadal variations of winter temperature in China are closely related to the basic flows and perturbations in the atmosphere.The possible mechanisms of the atmospheric general circulation influencing the winter temperature in China are discussed and the questions needed to be further studied are presented.