A New Possible Negative Feedback MechanismResponsible for the ENSO Cycle
一种新的ENSO循环负反馈机制

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.