东亚冬夏季风对热带印度洋秋季海温异常的响应

利用多年的Reynolds月平均海表温度资料和NCEP/NCAR全球大气再分析资料,分析了热带印度洋秋季海表温度距平(SSTA)与后期东亚冬夏季风强度变化的关系。结果表明,热带印度洋秋季SSTA的主要模态是全区一致(USB)型和偶极子(IOD)型,USB型模态主要代表热带印度洋秋季SSTA的长期变化趋势,而IOD型模态主要反映热带印度洋秋季SSTA的年际变化。热带印度洋秋季海温气候变率中既存在着明显的ENSO信号,也有独立于ENSO的变率特征,独立于ENSO的热带印度洋秋季SSTA变化的主要模态仍是USB型和IOD型。前期秋季USB模态与东亚冬季风及东亚副热带夏季风之间为负相关关系;与前期正(负)IOD模态相对应,南海夏季风强度偏弱(强),而东亚副热带夏季风强度偏强(弱)。USB型和IOD型模态对后期东亚冬、夏季风强度变化的影响是独立于ENSO的,但ENSO起到了调节二者相关显著程度的作用。

Responses of East Asian winter and summer monsoons to autumn sea surface temperature anomalies in tropical Indian Ocean

The relationships between autumn sea surface temperature(SST) anomalies in the tropical Indian Ocean and the strength of the East Asian winter and summer monsoons are investigated by analyzing Reynolds monthly SST dataset and NCEP/NCAR atmospheric reanalysis data.The results show that there are two dominant modes of autumn SST anomalies in the tropical Indian Ocean,the unanimous signed basin-wide(USB) mode and the Indian Ocean dipole(IOD) mode,respectively.The USB mode mainly shows a long term warming tendency of the tropical Indian Ocean,while the IOD mode reveals the interannual variations.By removal of ENSO-dependent variability,the SST anomalies in the tropical Indian Ocean mainly appear to be the USB and IOD modes.The USB mode exhibits significant negative correlations with the strength of the East Asian winter monsoon and the East Asian subtropical summer monsoon.When the positive(negative) IOD exists in the tropical Indian Ocean during the preceding boreal fall season,the South China Sea summer monsoon is weakened(strengthened),and the East Asian subtropical summer monsoon is strengthened(weakened).The relations of the dominant modes to the strength of the East Asian winter and summer monsoons are ENSO-independent variable,but the significance of the correlation can be modulated by ENSO.