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中文摘要：
利用NCEP／NCAR月平均再分析资料，研究冬季对流层上层西风急流的时空变化特征，提出表征急流强度和位置变化的指数，进而探讨西风急流与东亚冬季风的关系。结果表明：冬季西风急流强度指数体现了西太平洋与高纬大陆的热力对比，较好地反映了西伯利亚高压与阿留申低压的强度变化，可作为表征冬季风强弱变化的一个定量指标，急流增强（减弱）对应西伯利亚冷高压和阿留申低压加强（减弱），东亚冬季风偏强（弱）。急流强度指数与不同高度冬季风子系统的显著相关表明，东亚冬季风活动异常不只是对流层中低层的现象，而在整个对流层都有明显反映，低层的西伯利亚高压和阿留申低压、中层的欧亚脊、东亚大槽及西太平洋副热带高压与高层的西风急流是同相变化的。在此基础上还比较了急流强度指数和北极涛动指数（AO）与东亚冬季风的关系，急流强度变化体现了欧亚大陆与西太平洋的热力差异，而AO则主要反映极地与中纬度环状模的反相变化，所以急流强度变化与东亚冬季风的关系更为密切。
英文摘要：
The spatial and temporal variation characteristics of the East Asian subtropical upper-tropospheric westerly jet （EAWJ） in winter are examined by using the NCEP/NCAR monthly reanalysis data. The intensity index of the EAWJ is defined as the time coefficient of the first EOF eigenvector of the zonal wind at 200 hPa for investigating its association with the East Asian Winter Monsoon （EAWM）. The results indicate that the intensity index of the EAWJ is in accordance with the thermal contrast between western Pacific ocean and the continent over high-latitudes, which is reflected in the intensity variations of the Siberian cold high and the Aleutian low pressure. The significant correlations between the intensity index of the EAWJ and sub-systems at different levels of the EAWM reveal that the EAWM is a deep system with the in-phase variations of intensity of the Siberian cold high and Aleutian low pressure at low level, the East Asian trough and European ridge at middle level and EAWJ at upper level. Moreover, the decadal and interannual components of the intensity index of the EAWJ and Arctic oscillation （AO） index, and their relationships with the EAWM are compared. The intensity index of the EAWJ mainly reflects the thermal contrast of the East Asia regions whereas the AO reflect the out-phase variation between the SLP at polar region and that at midatitudes, which implies that the EAWM is rather closely related with the former than the latter. Furthermore, there exists the significant negative correlation at decadal scale components of the intensity index of the EAWJ and that of AO index, which is possibly linked with the variation of the thermohaline circulation in the Atlantic Ocean and need further study.
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