The Role of the Western Boundary in the ENSO Cycle: Experiments with Coupled Models

Abstract

Abstract Coupled models of the Pacific ocean–atmosphere system have been shown to produce oscillations in the model coupled system that resemble the observed El Niño–Southern Oscillation (ENSO) cycle in many respects. The tendency for the coupled models to oscillate is due to delayed negative feedback resulting from the reflection of Rossby wave activity from the western boundary. In the real ocean the reflection process is difficult to observe. Furthermore, among other potential complications affecting the generation and propagation baroclinic waves, the real western boundary is ragged with unknown reflective characteristics rather than the efficiently reflecting boundaries found in the oceanic components of the simple coupled models that produce ENSO-like oscillations. Thus, the validity of the delayed negative feedback–coupled oscillator concept remains open to question. We present the results of experiments with two coupled models, one simple and one more complex, in which realistic western equatorial...