一种新的ENSO循环负反馈机制  

A New Possible Negative Feedback Mechanism Responsible for the ENSO Cycle

作　　者：杨修群[1] 谢倩[1] 黄士松[1] 

机构地区：[1]南京大学大气科学系,南京空军气象学院气象系

出　　处：《大气科学》1996年第1期79-89,共11页Chinese Journal of Atmospheric Sciences

基　　金：国家攀登项目;国家自然科学基金

摘　　要：本文利用包含海洋表面边界层和大气辐合反馈过程的热带太平洋海气耦合异常模式的３０年模拟结果，通过对模式ＥＮＳＯ循环演变特征和正负反馈机制的细致分析，揭示出了ＥＮＳＯ循环形成的一种新的负反馈过程。指出：ＥＮＳＯ循环的正反馈机制是不稳定海气相互作用过程，且这一不稳定过程的发展在暖态中明显强于冷态；ＥＮＳＯ循环的负反馈机制在冷暖态中表现不同，在冷态消亡过程中，这种负反馈过程主要表现为暖的西传Ｒｏｓｓｂｙ波经西边界反射产生的暖的东传Ｋｅｌｖｉｎ波来抑制冷位相不稳定发展的，但在暖态消亡过程中，不存在类似的纬向波作用过程，其负反馈过程主要表现为在海气耦合不稳定充分发展时伴随的赤道两侧冷水上翻过程的加强以及非线性过程的衰减作用共同抑制了不稳定的发展，并最终使系统从暖态恢复至冷态。本文得出的ＥＮＳＯ循环暖位相中的负反馈机制和近年来国外提出的＂时滞振子＂理论明显不同。A tropical Pacific coupled air-sea anomaly model is integrated to 30 years.The ENSO cycle and its variability are successfully simulated.Based on the simulated results,the positive and negative feedback mechanisms responsible for the model ENSO cycle are analyzed and a new possible negative feedback mechanism is proposed.It is pointed out that the positive feedback mechanism for development of ENSO cycle is the unstable air-sea interaction and the process appears to be much stronger in the warm phase than in the cold phase.On the other hand,the negative feedback mechanism to check the unstable air-sea interaction in the warm phase of the ENSO cycle obviously differs from that in the cold phase.During the damping period of the cold state,the mechanism is related to the delayed effect produced by the wave reflection at the western boundary.However,during the damping period of the warm state,instead of reflection effect,the accompanied anomalous upwelling of cold water on the two sides of the equator with the strong development of unstable air-sea interaction at the equator and the nonlinear damping effect jointly restrain the instability and finally draw the system from the mature warm phase to the weak cold phase.The new possible negative feedback machanism for the ENSO cycle presented in this paper is very different from that described by the theory of delayed oscillator.

关 键 词：ENSO循环 正负反馈 形成机制 海气耦合 

分 类 号：P732.6[天文地球—海洋科学]