印度与东亚夏季风环流对ENSO及其年代际异常响应的数值研究

The Numerical Simulation of the Responding of Indian and East-Asian Summer Monsoon Circulation to ENSO and interdecadal Variation

根据诊断分析结果，利用ＬＡＧＳ改进的Ｌ９Ｒ１５气候诸模式，设计了３个数值试验，讨论了不同的年代际背景下ＥＮＳＯ异常对亚洲夏季风环流的影响。研究表明不同背景的ＥＮＳＯ异常与亚洲夏季风活动存在密切的关系。在冷背景条件下，当ＥＮＳＯ处于发展时，印度夏季风偏弱，风速较小，降水量偏少。而东亚夏季风偏南气流较强，受低气压控制，有利于气流辐合，降水量偏多。在ＥＮＳＯ衰减期，印度夏季风仍偏弱，风速偏小，具有干旱的趋势，而东亚夏季风区大陆仍为低气压控制，风速略有减小，降水量比正常年多，而比ＥＮＳＯ前一年有减少的趋势。在暖背景条件下，在ＥＮＳＯ的发展期，印度季风区的海陆热力差很小，海陆的物质交流也较弱，气压梯度较冷时期要小得多，这样造成了较弱的夏季风，降水量也比正常年要小，东亚夏季风较正常年弱，降水量偏少；在ＥＮＳＯ的衰减期，在印度季风区产生很强的海陆热力差，不仅大陆受较强的低气压控制，而且也有较大的海陆气压差，这样一方面夏季风强度异常加强，风速加大，另一方面大陆地区的降水量猛增，造成严重的洪涝；东亚地区与印度大陆相一致，同样为低气压控制，由于东部海洋的气压加大，这样气压梯度力加大，所以东亚夏季风加强，降水量也比正常年多。

Based on L9R15 climatic model. the effect of ENSO events under the differentinterdecadal background on Asian summer monsoon circulation is discussed by three numerical exper-iments. The results show that Asian summer monsoon anomaly cor responding to ENSO events are different under the different interdecadal background. Under the cold background;; the Indiansummermonsoon (ISM) is weak with smaller wind and scaree preicipitation;; and the east Asian summer mon-soon (EASM) is strong with greater northward flow and abundant preicipitation at the increasing stageof ENSO events;; but both of ISM and EASM are weaker at the decreasing stage of ENSO events.Un-der the warm background;; the ISM is weak with small land-sea heating differenee and scarcepreicipitation;; and the EASM is also weak at the increasing stage of ENSO events;; but ISM is muchstronger with the land-sea heating difference;; zonal winds and preicipitation enhancing remarkably;;which is easy to lead to flood over the indian areas. At the same time the EASM is a little stronger thanthat in normal monsoon years.