Roles of tropical SST anomalies in modulating the western north Pacific anomalous cyclone during strong La Nia decaying years

This study re-explores the roles of tropical SST anomalies in modulating the anomalous cyclone over the Indo-western Pacific during strong La Nia decaying years via a series of numerical experiments. The results suggest that central to eastern equatorial Pacific cooling, western north Pacific (WNP) warming, and Indian Ocean cooling all contribute to the Indo-western Pacific cyclonic wind anomalies. The WNP SST anomalies play a role via a Rossby wave-type response. As the positive SST anomalies in the WNP decay, the local forcing effect decays as well. The Indian Ocean remote forcing seems to play an important role during boreal summer via cold Kelvin wave induced cyclonic shear and boundary layer convergence. During strong La Nia decaying years, the negative SST anomalies in the equatorial central to eastern Pacific can maintain and persist into summer. Such cooling could induce anomalous Walker circulation with ascending branch over the Maritime Continent to Philippines and descending branch over central to eastern Pacific, which links the WNP climate to the equatorial central and eastern Pacific SST anomalies. The convective heating over the WNP induced remotely by central to eastern Pacific cooling in turn forces atmospheric Rossby wave to its west, which may amplify the anomalous cyclone over the Indo-western Pacific.