Persistence and breakdown of the western North Pacific anomalous anticyclone during the EP and CP El Nino decaying spring

The western North Pacific anticyclone (WNPAC) is the key bridge that connects El Nino to the East Asian climate anomalies. The persistence and breakdown of the WNPAC has important implications for climate prediction. Our results show that the eastern Pacific (EP) El Nino-induced WNPAC has good persistence in spring, whereas the central Pacific (CP) El Nino-induced WNPAC has an obvious breakdown in spring. The physical mechanisms behind this discrepancy are explored. During the EP El Nino spring, there are strong negative sea surface temperature anomalies (SSTAs) over the western North Pacific (WNP) and strong positive SSTAs over the EP. The negative WNP SSTAs suppress the convection over the WNP and then generate the WNPAC as a Rossby wave response. The positive EP SSTAs also cause suppressed convection over the western Pacific via the anomalous Walker circulation and then yield a WNPAC. In contrast, for the CP El Nino, the local air-sea positive feedback between the WNP SST cooling and the WNPAC in the CP El Nino winter is much weaker than in the EP El Nino winter, leading to the quick decay and disappearance of the WNP SST cooling in spring, which interrupts the WNPAC formation. In addition, with the westward shift of the SST warming to the central Pacific, the induced suppressed convection via the anomalous Walker circulation correspondingly moves westward around the Philippines, not around the western Pacific, which is not in favor of generating a remarkable WNPAC. Thus, a breakdown of the WNPAC is often observed for CP El Nino spring.