Effect of Northeast Pacific Wind on the Improvement of El Nino Prediction in a Climate Model

The role of the northeast Pacific wind in the dynamics of El Ni & ntilde;o has been proposed in previous theoretical studies. However, the actual effect of northeast Pacific wind on improving El Ni & ntilde;o prediction remains unclear, and the mechanisms through which northeast Pacific improves El Ni & ntilde;o predictions are not fully understood. In this study, we investigate the role of northeast Pacific wind in improving El Ni & ntilde;o prediction. By utilizing CESM that assimilates the northeast Pacific wind, the model improves prediction skills of ENSO indices at a lead time of 6-12 months, with a correlation three times higher than the predictions without nudged northeast Pacific wind. Nudging northeast Pacific wind in the model enhances the prediction of central Pacific (CP) El Ni & ntilde;o, thus leading to approximately 30% increase in the hit ratio of correct prediction of El Ni & ntilde;o. However, the model overestimates CP El Ni & ntilde;o predictions when the nudged northeast Pacific wind is incorporated. The mechanisms for the improvement of northeast Pacific wind in El Ni & ntilde;o predictions are investigated. In spring, El Ni & ntilde;o development is attributed to the wind-evaporation-SST (WES) feedback and oceanic downwelling induced by subtropical westerly wind stress. In contrast, during summer, El Ni & ntilde;o development is dominated by the summer deep convection (SDC) response. During subsequent summer-autumn, anomalous surface latent heat flux related to wind speed and net shortwave radiation associated with the low cloud-SST feedback contribute to El Ni & ntilde;o development. These processes are more favorable for CP El Ni & ntilde;o development. This study implies that accurately simulating air-sea coupling associated with northeast Pacific wind may be an effective approach in improving El Ni & ntilde;o prediction.