中文摘要：

大气季节内振荡（MJO）对东亚季风的活跃、推进和中断具有显著影响,然而其在东亚季风爆发中的作用一直没有得到深入探讨.利用经验正交函数（EOF）分解和超前滞后回归分析方法,探讨了1979 2011年4-6月MJO的北传与东亚季风爆发的关系.研究表明：4-6月MJO有两次明显的北传过程,分别发生在5月中旬和6月中旬.逐候向外长波辐射资料EOF分析的前两个模态对应了MJO的不同位相,可以表征MJO的向东向北传播.超前滞后回归分析表明,伴随MJO的北传,降水带北移、印度洋到我国南海地区西南风建立、西太平洋副热带高压撤出南海及南亚高压北抬,这些环流异常形势有利于东亚季风的爆发.进一步对PC1所确定的季风爆发候与其它5个季风爆发指数进行对比发现,在大多数年份中,PC1所确立的季风爆发候与其它指数相差2候以内,其中,与其它5个指数所表征的季风爆发时间严格一致的年份分别有15、10、11、10、12年,表明MJO对东亚季风的爆发具有普遍作用.

英文摘要：

Madden-Julian Oscillation （MJO） has a significant impact on the active,advancing and break phase of the monsoon in the East Asian region.However,the influence of MJO on monsoon onset is still an outstanding issue.By using the empirical orthogonal function （EOF） and lead-lag regression analysis,this paper analyses the relationship between the northward propagation of MJO and East Asian monsoon onset （EAMO）.The main findings are as follows.There are two obvious northward propagation processes of MJO in April to June,which occur in the middle periods of May and June,respectively.The first two EOF leading modes of pentad outgoing longwave radiation are corresponding to the different MJO phases,which represent the propagation of the MJO.In the process of the northward propagation of MJO,the positive anomalies of precipitation tend to shift northward,along with the shift of anomalous easterly wind to the westerly in the lower troposphere of Indian Ocean,the onset of the south-west wind in the Bay of Bengal and South China Sea,the eastward retreat of the Western Pacific Subtropical High and the northward shift of the South Asia High.The above features indicate that the northward propagation of the MJO may strengthen the EAMO to some extent.The monsoon onset dates determined with PC1 are compared with those with the other five indices with the finding that MJO has a common effect on the EAMO.The difference between PC1 and other five indices is less than 2 pentads in most years.For strictly consistent monsoon outbreaks between PC1 and other five indices,they are 15,10,11,10,12 years,respectively.Key words：East Asian monsoon,MJO,northward propagation