Bifurcations in a low-order nonlinear model of tropical Pacific sea surface temperatures derived from observational data.

ABSTRACT

Aiming at tackling the difficulty in exactly constituting the sea surface temperature (SST) dynamical model, the paper introduces the dynamical system reconstruction idea and establishes the nonlinear dynamical model of SST field based on 1963-2010 monthly average Hadley SST data. Time coefficients series after empirical orthogonal functions decomposition are taken as the dynamical model variables and Genetic Algorithms is used to optimize and retrieve the model parameters. The stability of the equilibrium in the reconstructed model is analyzed and dynamical actions such as bifurcation and mutation are discussed. Also the activity configuration and aberrance mechanism of the SST field are developed upon the actual activity characteristics of the SST field in the Tropical Pacific Ocean in that year. Results reveal that the bifurcation action of the SST field system from one stable high-value equilibrium to another stable low-value equilibrium accords with the La Niña process while the mutation action of the SST field system from two stable equilibriums to another stable equilibrium accords with the El Niño process.