Possible Influence of the Indian Ocean Dipole on Western North Pacific Tropical Cyclone Activity

While the influence of basin‐wide sea surface temperature (SST) anomalies in the Indian Ocean on tropical cyclones (TCs) in the Western North Pacific (WNP) has been extensively studied, the impact of the Indian Ocean Dipole (IOD) mode on WNP TC activity remains less well understood. In this study, we use best‐track and reanalysis data to investigate the effects of the IOD on WNP TC activity during the peak typhoon season (July–October) over the period 1965–2023. Given the strong interconnection between the El Niño–Southern Oscillation (ENSO) and the IOD, we remove the influence of ENSO through linear regression to isolate the independent impact of the IOD. Results show that during the positive phase of the IOD, TC genesis is associated with an increase over the South China Sea but suppressed in the ocean to the east of the Philippines. This spatial shift in TC genesis, along with an anomalous cyclonic steering flow over the western WNP, leads to increased TC activity influencing northern China. The suppressed TC genesis east of the Philippines is largely driven by enhanced vertical wind shear, resulting from strengthened low‐level westerlies and upper‐level easterlies associated with suppressed convective heating over the eastern pole of the IOD. Meanwhile, the positive IOD phase enhances the WNP monsoon and increases low‐level vorticity over the South China Sea, favoring TC development in this region. These findings suggest that the IOD can modulate spatial distribution and regional characteristics of TC activity over the WNP, offering important insights into the climatic variability of WNP TCs.