ENSO dynamics: low-dimensional-chaotic or stochastic?

TL;DR

This paper investigates whether ENSO dynamics are low-dimensional and deterministic or high-dimensional and stochastic, finding evidence for stochastic behavior and emphasizing the role of atmospheric randomness in models.

Contribution

It demonstrates that ENSO dynamics are better characterized as stochastic and highlights the importance of stochastic forcing in low-dimensional models.

Findings

ENSO dynamics are high-dimensional/stochastic.

Stochastic forcing reproduces ENSO features in models.

Deterministic models lack key stochastic aspects.

Abstract

We apply a test for low-dimensional, deterministic dynamics to the Nino 3 time series for the El Nino Southern Oscillation (ENSO). The test is negative, indicating that the dynamics is high-dimensional/stochastic. However, application of stochastic forcing to a time-delay equation for equatorial-wave dynamics can reproduce this stochastic dynamics and other important aspects of ENSO. Without such stochastic forcing this model yields low-dimensional, deterministic dynamics, hence these results emphasize the importance of the stochastic nature of the atmosphere-ocean interaction in low-dimensional models of ENSO.