A delay differential model of ENSO variability: parametric instability and the distribution of extremes - Université Pierre et Marie Curie Accéder directement au contenu
Article Dans Une Revue Nonlinear Processes in Geophysics Année : 2008

A delay differential model of ENSO variability: parametric instability and the distribution of extremes

Résumé

We consider a delay differential equation (DDE) model for El-Niño Southern Oscillation (ENSO) variability. The model combines two key mechanisms that participate in ENSO dynamics: delayed negative feedback and seasonal forcing. We perform stability analyses of the model in the three-dimensional space of its physically relevant parameters. Our results illustrate the role of these three parameters: strength of seasonal forcing b, atmosphere-ocean coupling ?, and propagation period t of oceanic waves across the Tropical Pacific. Two regimes of variability, stable and unstable, are separated by a sharp neutral curve in the (b, t) plane at constant ?. The detailed structure of the neutral curve becomes very irregular and possibly fractal, while individual trajectories within the unstable region become highly complex and possibly chaotic, as the atmosphere-ocean coupling ? increases. In the unstable regime, spontaneous transitions occur in the mean "temperature" (i.e., thermocline depth), period, and extreme annual values, for purely periodic, seasonal forcing. The model reproduces the Devil's bleachers characterizing other ENSO models, such as nonlinear, coupled systems of partial differential equations; some of the features of this behavior have been documented in general circulation models, as well as in observations. We expect, therefore, similar behavior in much more detailed and realistic models, where it is harder to describe its causes as completely.
Fichier principal
Vignette du fichier
npg-15-417-2008.pdf (1.06 Mo) Télécharger le fichier
Origine : Accord explicite pour ce dépôt
Loading...

Dates et versions

hal-00331120 , version 1 (18-06-2008)

Identifiants

  • HAL Id : hal-00331120 , version 1

Citer

M. Ghil, I. Zaliapin, S. Thompson. A delay differential model of ENSO variability: parametric instability and the distribution of extremes. Nonlinear Processes in Geophysics, 2008, 15 (3), pp.417-433. ⟨hal-00331120⟩
278 Consultations
133 Téléchargements

Partager

Gmail Facebook X LinkedIn More