西伯利亚高压的长期变化及全球变暖可能影响的研究

LONG TERM VARIABILITY OF THE SIBERIAN HIGH AND THE POSSIBLE CONNECTION TO GLOBAL WARMING

本文利用历史海平面气压资料建立了近百年来的西伯利亚高压强度指数。１９６０年代是近百年来西伯利亚高压强度最强的一段时期，１９８０年代后期到１９９０年代则是近百年来最弱的一段时期。４０年左右的年代际变化比较明显。用西伯利亚高压强度能较好地解释近几十年来我国冬季气温变化的特征。近百年来西伯利亚高压的变化可能仍然以自然变率为主，全球变暖的影响还较弱。但是，在全球持续变暖的情景下，西伯利亚高压的强度将会显著减弱，５年～６年左右年际尺度的变率将会加强。

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 n cos φ n? 苮72n=1δ n cos φ 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 CO 2 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 Co 2, variability at 5￣6 year inter annual scale can be expected to become more prevalent.