ENSO Nonlinearity

Describing ENSO as a damped linear oscillator perturbed by stochastic forcing is becoming one of the prevailing views of ENSO. Some observational evidence is presented to illustrate that nonlinear dynamics process of ENSO should not be neglected and it does play an essential role in generating the significant asymmetry in the ENSO cycle. The nonlinear rectification of ENSO projects significantly on the interdecadal climate variability in the tropical Pacific. Nonlinear scenarios that allow large amplitude modulations of ENSO are also explored with discussions on the possible nonlinear feedback between the decadal changes in climate state and ENSO activity. The impact of weather noise will be also addressed.