Enhanced Impact of Western North Pacific Tropical Cyclones on El Niño Intensity in the Past 40~Years

Tropical cyclones (TCs) in the western North Pacific (WNP) can modulate the intensity of ENSO by weakening the Walker circulation and exciting or enhancing the eastward oceanic Kelvin waves. We find that WNP TCs have played an increasingly important role in the development of El Nino over the past 40 years, and that TCs contribute more to atmospheric circulation, SST and thermocline depth anomalies. The accumulated cyclone energy (ACE) in the WNP shows an enhanced explanatory capability for the Nino 3.4 index. TCs excite oceanic Kelvin waves with greater amplitudes compared to the past. Through diagnostic analysis of the temperature tendency equation, it is also found that TCs contribute more strongly to thermocline feedback and zonal advection feedback three months later. Consequently, it can be concluded that TCs play an increasingly significant positive feedback role in ENSO dynamics in the current climate context.

Atmospheric Research