How Central and Eastern Atlantic Niño Differently Shape Western North Pacific Tropical Cyclones

The Atlantic Niño, a climate pattern involving periodic warming of the tropical Atlantic Ocean, can be categorized into two main types based on where the warming is strongest: in the central (CA) or eastern (EA) basin. Our research investigates whether these two types have different effects on Pacific typhoons. We find that they indeed drive very distinct impacts. Composite and correlation analyses indicate that CA events induce a meridional dipole in TC formation, while EA impacts are weaker and less organized. The results reveal a clear meridional dipole pattern in TC genesis associated with the two types of Atlantic variability. Specifically, CA events exert a pronounced influence, enhancing TC genesis north of 20°N during CA Niño and south of 20°N during CA Niña. After removing the linear influence of ENSO, the relationship between Atlantic variability and TC activity weakens substantially for ATL3 and EA indices, whereas it remains robust for the CA index, suggesting a more direct and independent teleconnection pathway for CA events. CA Niño efficiently excites a well-structured extratropical Rossby wave train that reaches the WNP, whereas EA signals are weaker and more diffuse. Both CA and EA events are associated with a Walker-type circulation linking the tropical Atlantic and Indo–Pacific. CAM4 sensitivity experiments further support these findings, demonstrating that CA-type SST forcing can reproduce the key tropical–extratropical response extending into the WNP, whereas the EA-type forcing yields a substantially weaker adjustment. Overall, these results demonstrate that CA and EA events exert fundamentally different influences on Pacific atmospheric circulation, with CA variability playing a more dominant role in modulating WNP TC genesis.