Predicting the '97 El Nin̈o event with a global climate model

Abstract

A simple data assimilation technique has been applied for initializing coupled ocean-atmosphere general circulation models, which is able to generate the three-dimensional thermal state of the low-latitude oceans by forcing the model with observed anomalies of sea surface temperature. The scheme has been tested in a multi-year experiment in which the vertical temperature profiles in the equatorial Pacific measured by the TOGA-TAO array have been successfully reproduced for the period '96 to '97. In a further series of eight hindcast experiments initialized between January '96 and September '97, the predictive skill of the model was tested. All experiments starting in '97 correctly simulated the evolution of the '97 El Niño, although the amplitude was slightly underestimated. While the ocean was pre-conditioned to create an El Niño already in '96, the model correctly stayed in the cold (La Niña) phase initially. All experiments initialized in '97 forecast a La Niña event for the middle of '98. Copyright 1998 by the American Geophysical Union.