中文摘要：

采用全印度陆地降水资料、NCEP/NCAR大气资料以及HadISST资料集的SST资料,使用经验正交函数分解(EmpiricalOrthogonalFunction,EOF)和相关分析回归分析等统计方法,在前人的基础上,系统研究了厄尔尼诺-南方涛动(ElNino-SouthernOscillation,ENSO)及印度洋海盆模态(IndianOceanBasinmode,IOB)对印度夏季季风降水的影响,指出厄尔尼诺衰退年印度夏季降水在反对称模态和北印度洋二次增暖共同的作用下表现出初夏减少晚夏增加的特点。通过观测分析发现,厄尔尼诺在其发展年和衰退年对印度夏季季风降水的影响截然不同。在发展年,中东太平洋的异常增暖引起Walker环流的改变,印度洋区域的下沉气流抑制印度大陆降水。在衰退年,厄尔尼诺对印度洋进行“充电”,产生印度洋海盆增暖模态。在这个过程中,局地海气相互作用引起衰退年的印度降水有初夏减少晚夏增加的特点。其中春季印度洋的反对称风场(赤道以北为东北风异常,赤道以南为西北风异常)对印度夏季风有一定的减弱作用,这种异常环流减弱了初夏印度降水。同时反对称风场会造成在夏季北印度洋的二次增暖,又会促进了晚夏降水的异常增加。通过水汽输运通量的诊断分析进一步验证了上述海盆模态对印度夏季降水的作用。

英文摘要：

Based on the All India Rainfall data, NCEP/NCAR reanalysis data and HadISST data, we demonstrated a delayed effect of the El Nino-Southern Oscillation (ENSO) and Indian Ocean Basin (IOB) mode on Indian summer monsoon rainfall(ISMR). The results showed that decreased Indian rainfall in the early summer (Jun-Jul) and increased rainfall in the late summer (Aug-Sep) are influenced by the anti-symmetric mode and the second warming in the northern Indian Ocean (NIO).The responses of ISMR to El Ni?o are distinct between the developing and decaying years. In the developing year of El Ni?o,the ISMR decreases due to the change of Walker circulation in the tropical ocean. In the decaying year, the IOB mode decreases (increases) the ISMR in early (late) boreal summer. The anti-symmetric pattern of atmospheric anomalies with northeasterly (northwesterly) wind anomalies north (south) of the equator happens in spring. The northeasterly anomalies weaken the Indian Summer Monsoon and force the second anomalous sea surface temperature (SST) peak in the NIO by reducing wind speed and surface evaporation. The southwest monsoon brings more moisture (Q?), which is produced by the warm NIO SST to the India subcontinent, leading to increased monsoon rainfall in the late summer.