Abstract: The Siberian High is one of the most important circulation systems influencing the climate of eastern Asia in winter. In this study, the intensity index of the Siberian High is defined as I=? 苮72n=1P_nδ_ncosφ_n? 苮72n=1δ_n cosφ_n where P_n is the sea level pressure at grid n , φ_n is latitude, δ_n =1 when P_n ≥1 028 hPa, and δ_n =0 when P_n <1 028 hPa. This index indicates the level of anomaly from the average atmospheric conditions in the core region of the Siberian High. A long time series of the intensity index for the last hundred years was established on the basis of monthly mean sea level pressure data for the northern hemisphere obtained from CRU/UEA. Power spectrum analysis reveals that, for about four decades, the index showed decadal variability. In the 1960s, the Siberian High’s intensity was the highest. During the late 1980s and the early 1990s, the intensity was the lowest. The intensity was strongly correlated with the winter temperature of East Asia. A great deal of the temperature variance in the region 110°E～140°E and north of Bangladesh can be explained by the intensity index. Our calculation of the temperature data for 65 winters shows that 43 6 percent of the variance of North China’s winter mean temperature can be accounted for by the intensity of the Siberian High. The possible impact of global warming on the variability of the High was also investigated using the atmosphere ocean coupled general circulation model (HADCM2). The result of CO² increase at the rate of 1% per year on global warming was compared with the result of control integration. It was found that in the last hundred years the impact of global warming on the Siberian High was not evident and that the High’s own natural variability played a more important role. Continuous warming in the future will significantly reduce the intensity of the system. However, the change will not be linear. With increasing Co², variability at 5～6 year inter annual scale can be expected to become more prevalent.

Key words: Siberian High, climate variability, global warming