热带太平洋和印度洋海温异常对东亚冬季风影响的一个物理机制

A Mechanism for the Impact of Sea Surface Temperature Anomaly over Tropical Pacific and Indian Ocean on East Asian Winter Monsoon

本文利用NCEP/NCAR提供的大气环流资料和海表温度异常资料,在分析热带太平洋和印度洋海温异常与冬季大气环流之间关系的基础上提出了一个综合反映热带太平洋和印度洋海温异常的综合指数。分析表明,冬季太平洋和印度洋海温异常指数的值越大(小),东亚冬季风指数的值越大(小),东亚地区将出现异常的南(北)风的响应,东亚冬季风将越弱(强)。应用加热强迫影响热带环流的简单模式研究了热带太平洋印度洋异常海温对东亚冬季风影响的物理机制。结果表明,当冬季热带太平洋和印度洋海温异常指数处于正(负)位相时,西太平洋区域强迫出异常南(北)风。这是使得东亚冬季风偏弱(强)的重要原因之一。冬季热带太平洋和印度洋海温异常对东亚冬季风影响最为显著的关键区是赤道西太平洋。

After the relationship between sea surface temperature anomaly （SSTa） over tropical Pacific and Indian Ocean and East Asian winter monsoon （EAWM） had been analyzed with atmospheric circulation and SSTa data provided by NCEP/NCAR, an Index reflecting the co- variation of sea surface temperature anomaly over tropical Pacific and Indian Ocean was introduced. The analysis results indicted that, when the index is larger （smaller） than normal, the EAWMI is often larger （smaller） than normal, and the abnormal south （north） wind appears over East Asia, which leads the EAWM is weaker （stronger） than normal. The mechanism was obtained with simple model eonsidering the impact of heating on tropical atmospheric circulation. The result shows that the abnormal south （north） wind will be forced out when the SSTa index is in positive （negative） phase, which is one of the most significant impacts on EAWM. The tropical Western Pacific is the key area which influences the EAWM.