中文摘要：

利用站点降水资料、美国气候预测中心（CPC）的MJO指数和NCEP/DOE AMIP-II再分析资料,研究了热带印度洋MJO对4—6月长江中下游地区降水的影响及可能机制。（1）热带印度洋MJO对长江中下游地区降水有显著影响：热带印度洋MJO偏强（偏弱）时,同期以及滞后1~2候时该地区降水偏多（偏少）。（2）热带印度洋MJO处在不同位相时,大尺度背景场有明显的差别：热带印度洋MJO偏强（偏弱）时,同期以及滞后1~2候时MJO活跃对流中心位于热带印度洋（西太平洋）,西太平洋副热带地区表现为反气旋性（气旋性）环流异常,孟加拉湾为气旋性（反气旋性）环流异常,长江中下游地区出现了异常上升（下沉）运动,水汽辐合增强（减弱）;伴随MJO的东传,水汽输送异常来源有所变化。（3）热带印度洋MJO通过激发Gill型响应和Rossby波列,对长江中下游地区降水产生影响。

英文摘要：

The impact of the tropic Indian Madden-Julian oscillation（MJO） on the precipitation of the middle and lower reaches of Yangtze River（MLYR） during April-June and its possible mechanism are investigated using the observational rainfall data, the pentad MJO indices, and the NCEP/DOE AMIP-II Reanalysis. The results show that when the tropical Indian MJO is active（inactive）, the rainfall of the MLYR is enhanced（suppressed） in the same period and the following two pentads. Such different rainfall regimes are associated with the corresponding changes in large scale background fields. When the tropical Indian MJO is active（inactive）, an anomalous anticyclone（cyclone） develops in the western North Pacific and an anomalous cyclone（anticyclone） arises in the Bay of Bengal. The water vapor convergence and upward motion in the MLYR are increased（decreased）, being in favor of rainfall enhancement（suppression）. It is suggested that the tropical Indian MJO may influence the precipitation of the MLYR during April-June by forcing the classical Matsuno-Gill solution and a Rossby wave train.