Impact of western North Pacific variability and East Asian cold surges on development of ENSO

The present study uses reanalysis data to investigate how the East Asian cold surges are linked to the initiation of westerly wind anomalies prior to El Niño events and easterly wind anomalies prior to La Niña events in the western equatorial Pacific. Our analysis shows that East Asian cold surge events can be associated with the formation of an anomalous anticyclone that moves eastward across the North Pacific and cools the ocean surface prior to El Niño events. The outflow of the anomalous anticyclonic circulation is responsible for the initiation of westerly wind anomalies in the western equatorial Pacific. We also find that East Asian cold surge events are involved in the development of an anomalous cyclone that moves northeastward along the subpolar North Pacific and reinforces the horizontal temperature gradient prior to La Niña events. The cross-equatorial flow into the anomalous cyclone in the North Pacific contributes to the development of easterly wind anomalies in the western equatorial Pacific. We show that air-sea interactions can play a role in the propagation of anomalous circulations across the North Pacific, eventually initiating zonal wind anomalies in the western equatorial Pacific.