How Much of the Interannual Variability in Western North Pacific Tropical Cyclone Activity Is Driven by Sea Surface Temperature? Evidence From CMIP6 HighResMIP Simulations

Abstract Tropical cyclone (TC) activity over the western North Pacific (WNP) exhibits substantial interannual variability, often attributed to sea surface temperature (SST) anomalies across the global oceans. However, the extent to which this variability can be driven by SST forcing remains unclear. Here we examine WNP TC activity simulated by five high‐resolution atmospheric models from the High Resolution Model Intercomparison Project, all of which are forced by observed SSTs. These SST‐forced simulations collectively reproduce key climatological characteristics of WNP TC activity, including their spatial distribution and seasonal evolution. On interannual timescales, the multi‐model mean captures variations in TC genesis frequency, track frequency, and power dissipation index over 1980–2014, with statistically significant correlation coefficients of 0.51, 0.62, and 0.65, respectively—indicating that SST forcing can account for approximately 30%–40% of the observed variability. This SST‐driven variability is closely linked to realistic simulations of large‐scale environmental conditions, as quantified by the dynamic genesis potential index, which largely controls both the spatial distribution and temporal variability of TC genesis. Further analysis reveals that trans‐basin SST anomalies—particularly those associated with the Pacific Meridional Mode, the Indian Ocean, and the North Atlantic—play a dominant role in modulating these large‐scale environments. Nonetheless, over half of the interannual variance in TC activity cannot be forced by SST, highlighting the limits of SST‐based seasonal prediction. These results underscore the importance of SST forcing while also pointing to the need for improved understanding of additional drivers of WNP TC variability.