夏季中国华北降水、印度降水与太平洋海表面温度的耦合关系

本文基于1951~2014年的站点观测资料以及再分析资料，应用多变量经验正交分解法（MEOF）研究了年际尺度上华北夏季降水、印度夏季降水与海表面温度之间的耦合关系（主要模态）。结果表明:当印度夏季降水偏强时，若同期夏季赤道中东太平洋海温表现为La Ni?a位相，则西太平洋暖池对流加强，副热带高压偏西偏北，有利于华北夏季降水与印度夏季降水一致增强。反之，当印度大部降水偏弱时，若同期夏季赤道中东太平洋海温表现为El Ni?o位相，则华北夏季降水和印度夏季降水一致减弱。然而，两地夏季降水的协同变化关系并不总是成立。当赤道中东太平洋海温异常随时间演变表现为冬春El Ni?o衰减型时，伴随着印度洋偶极子（IOD）正位相的衰减过程，这会减弱东亚夏季风，使得华北夏季降水偏少。此时印度半岛夏季降水增强区集中在其西部，无法形成连接印度和华北夏季降水异常的环半球遥相关（CGT）波列，可能使得华北夏季降水异常与全印度夏季降水异常成相反形势。这些结论揭示了中国华北夏季降水、印度夏季降水和海表面温度之间的耦合关系，有助于进一步理解海温外强迫对两地夏季降水之间相关关系的作用，从而对华北夏季降水的预测具有参考意义。

A Study on the Coupling Relationships among the Pacific Sea Surface Temperature and Summer Rainfalls over North China and India

Based on 1951-2014 reanalysis and observational datasets, the coupling relationships among the summer rainfalls over North China (NCSR) and India (ISR) and global sea surface temperature (SST) are analyzed. With the multivariate empirical orthogonal function (MEOF) method, the dominant coupling modes among NCSR, ISR and SST have been identified. The results show that there exist significant coupling relationships among them on the interannual scale. The NCSR and ISR tend to increase/decrease synchronously under La Niña/El Niño condition with cooler/warmer SST over the central and eastern equatorial Pacific in the concurrent summer. However, such a relationship between NCSR and ISR does not always hold. If the SST pattern is in the decaying phase of the El Niño event from the preceding winter to spring, summer rainfall over western India increases but the NCSR is likely to decrease. It is accompanied by the weakening of the positive phase of Indian Ocean Dipole (IOD) from the preceding winter, which weakens the East Asia summer monsoon in the concurrent summer. In addition, the circumglobal teleconnection pattern (CGT) connecting ISR and NCSR is inactive, since the above-normal ISR mainly occurs over western India. These results are helpful for in-depth understanding of the role SST plays in the relationship between the summer rainfalls over North China and India, and thus provide some clues for the prediction of North China summer rainfall.