印度洋-太平洋海表温度年际变化的联合模态

Joint Modes of the Pacific-Indian Ocean Sea Surface Temperature Anomaly at Interannual Timescale

利用1870-2004年的HadiSST的月平均海表面温度（SST）资料，对去除了全球增暖趋势的印度洋一太平洋海表温度异常（SSTA）作季节经验正交函数（Season—reliant Empirical Orthogonal Function，S-EOF）分解，得到了印度洋一太平洋海表温度年际变化的2个联合模态，并且分析了与之相对应的大气环流特征。结果表明：低频的厄尔尼诺／南方涛动（ENSO）是控制印度洋一太平洋的主导模态，能使赤道印度洋维持一异常反气旋性环流，削弱印度洋夏季风的作用并且将东印度洋暖池的暖水输送到西印度洋，印度洋SSTA在一年四季中都出现全海盆同号变化，因此，第一主模态是ENSO的低频模与印度洋海盆一致模的联合模态；第二模态表现为太平洋上准2a的ENSO位相转换模与印度洋偶极子模的联合模态，ENSO的位相转换发生于春季，与季风的异常转换有关，印度洋上出现异常的气旋性环流，叠加在印度洋夏季风上，增大东西印度洋的温差，在秋季出现西低东高的偶极子型海温分布，印度洋夏季风和这个模态的产生发展有很大的联系。

Based on the monthly mean sea surface temperature data removing linear trend from HadiSST during 1870 to 2004, two joint modes of the Pacific-Indian Ocean sea surface temperature anomaly at interannual timescale were analyzed with the application of the Season-reliant empirical orthogonal function （S-EOF） decomposition method. Results show that the low-frequency ENSO is the leading ajoint mode accompanying with the Indian Ocean basin mode. An anomalous anticyclone is hold over the equatorial Indian Ocean, which can weaken the Indian summer monsoon and transport the warm water in the eastern Indian warm pool to the west, further causes the Indian Ocean basin warming in all four seasons. The second joint mode is the transition mode of the ENSO with the India Ocean dipole mode. The phase of ENSO begins to change in boreal spring, when the monsoon is in the transition stage. Accordingly, an anomalous cyclonic cell appears over the India Ocean, which can enlarge the east-west SST difference of the equatorial Indian Ocean by enhancing the Indian summer monsoon. Based on the fact, the eastern Indian Ocean warming reaches its maximum in boreal autumn and a dipole mode appears. The India Ocean summer monsoon is closely related to the development of this mode.