北半球夏季副热带西风急流变异及其对东亚夏季风气候异常的影响

ANOMALIES OF THE EXTRATROPICAL WESTERLY JET IN THE NORTH HEMISPHERE AND THEIR IMPACTS ON EAST ASIAN SUMMER MONSOON CLIMATE ANOMALIES

探讨了东亚地区副热带西风急流 (EAJS)位置的年际变化特征、影响及其可能机制 .EAJS南北变动的影响主要集中在亚澳季风区和气候平均的北半球副热带西风急流轴的南北两侧 ,这与SOI或ENSO相联系的大气环流响应很不相同 ,后者的影响主要表现在中、东太平洋上 .北半球副热带西风急流存在着两个显著不同的模态 ,其中一个模态反映的是亚太尤其是东亚地区的西风急流的南北变异 ,另一个模态出现在 15 0°E～ 12 0°W的中、东太平洋上 .它们分别联系着不同的太平洋海温异常分布 ,但都能对夏季 2 0 0hPa南亚高压的强度产生影响 ,尤其是南亚高压的东部 。

We study the interannual variability of the extratropical westerly jet over East Asian (EAJS), its impacts and possible mechanisms. The impact of south north alternation of EAJS concentrates in the Asian Australian monsoon region and the two sides of the climatological position of EAJS, which is quite different from the atmospheric responsible of SOI(South Oscillation Index) or ENSO(El Nino South Oscillation). The impacts of the latter exhibit mainly in the middle and east Pacific. There exist two dominant modes of the summer subtropical westerly jet in the north hemisphere. The first deals with the south north alternation of the westerly jet in the Asia Pacific area, especially in the East Asia. The second mode appears in the mid east Pacific of 150°E～120°W. The two modes link with two significantly different SST patterns in the Pacific, but they can all influence the intensity of 200 hPa South Asian Anticyclone, especially the intensity of the east part of the South Asian Anticyclone, and which will contribute to the formation of summer floods and droughts in eastern China.