中文摘要：

利用1961～2000年的NCEP/NCAR候平均再分析资料,初步探讨了季节转换期间东亚副热带西风急流南北和东西向位置变化与亚洲季风爆发之间的联系。结果表明,亚洲夏季风爆发伴随着东亚副热带西风急流轴线的北跳和急流中心西移,急流轴北跳至35°N以北的青藏高原上空,南支西风急流消失,亚洲季风环流形势建立。南海季风爆发早年,低纬的东风向北推进的时间早,到达的纬度偏北,中纬的西风急流强度偏弱,季风爆发晚年则相反。同时,南海夏季风爆发早年,青藏高原上空急流核出现较早,西太平洋上空急流核减弱较快,急流中心“西移”较早。而在南海夏季风爆发晚年,西太平洋上空的急流核减弱较迟,青藏高原上空急流核形成偏晚,急流中心“西移”较迟。此外,急流中心东西向位置和强度变化与江淮流域梅雨的开始和结束也有密切关系。

英文摘要：

The relationship between the location change of the East Asian subtropical westerly jet （EASWJ） and Asian summer monsoon onset is investigated by using NCEP/NCAR pentad mean reanalysis data. The results show that the Asian monsoon onset is accompanied by the northward jump of the EASWJ axis and the westward movement of EASWJ center. When the EASWJ axis jumps northward to 35°N over the Tibetan plateau and the southern branch of the westerly disappears, the Asian monsoon circulation is established. In the early onset year of the South China Sea （SCS） monsoon, the tropical easterly advances northward early, reaches more northward latitude, and the mid-latitude westerly jet intensity is much weaker, whereas in the late onset year of the SCS monsoon, the situation is contrary. Meanwhile, the westerly jet core occurs early ,over the Tibetan plateau in the early SCS monsoon onset year, and the jet core over the western Pacific weakens rapidly, leading to early westward migration of the westerly jet center, wtlile in the late SCS monsoon onset year the westerly jet core occurs late over the Tibetan plateau, and the jet core over the western Pacific weakens slowly, leading to late westward migration of the westerly jet center. In addition, the EASWJ location and intensity changes in the longitudinal direction are also associated with the beginning and ending of the plum rain in the Yangtze and Huaihe river valley.