Working Group 3: ENSO Modelling and Prediction

The El Nino/Southern Oscillation (ENSO) is a phenomenon exhibiting near-global oscillations of sea level pressure and winds, with the largest amplitude in the tropical Southern Hemisphere. Most of the more intense manifestations of wind, sea surface temperature (SST) and precipitation occur in the tropical Pacific, and it is there that most of the modelling and prediction efforts have been concentrated. The ENSO phenomenon appears cyclic, having well-defined sequences of events, but is not periodic, the historical record showing irregularities and long periods of time during which ENSO oscillations did not occur. When ENSO oscillations do occur, the local effects on the coast of Peru are economically catastrophic, and there are indications that mid-latitude weather is affected by equatorial SST anomalies. Consequently, there is great interest in predicting the occurrence of ENSO in the equatorial Pacific.