Oral

IAPSO

JMP10 - Ocean-Atmosphere Mechanisms of Climate Variability, Change and Predictability

Effect of Northeast Pacific wind on the improvement of El Nino prediction in a climate model

The role of the Northeast Pacific wind on the dynamics of El Ni?o has been proposed in previous theoretical studies. However, the actual effect of Northeast Pacific wind on improving El Ni?o prediction remains unclear, and the mechanisms through which Northeast Pacific improves El Ni?o predictions are not fully understood. In this study, we investigate the role of Northeast Pacific wind in improving El Ni?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 three-time correlation higher than predictions without nudged Northeast Pacific wind. Nudging Northeast Pacific wind in the model enhances prediction of Central-Pacific (CP) El Ni?o, thus leading to an approximate 30% increase in the hit ratio of correct prediction El Ni?o. However, the model overestimates CP El Ni?o predictions when the nudged Northeast Pacific wind is incorporated. The mechanisms for the improvement of Northeast Pacific wind on El Ni?o predictions are investigated. In spring, El Ni?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?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?o development. These processes are more favorable for CP El Ni?o development. This study implies that accurately simulating air-sea coupling associated with Northeast Pacific wind may be an effective approach to improving El Ni?o prediction.