Modulation of ENSO–Tropical Cyclone Genesis Frequency Relationship by Sea Surface Warming of Different Spatial Patterns

Abstract El Niño–Southern Oscillation (ENSO) strongly modulates tropical cyclone genesis frequency (TCGF) at interannual time scales, yet how future sea surface temperature (SST) warming patterns may modify this relationship remains unclear. Here, we use high-resolution climate model simulations to quantify how three distinct SST warming patterns—uniform warming, El Niño–like warming (characterized by enhanced central/eastern Pacific warming), and La Niña–like warming (characterized by suppressed central/eastern Pacific warming)—alter the ENSO–TCGF linkage. We define a strengthening of the ENSO–TCGF relationship as an increase in the magnitude of the TCGF difference between El Niño and La Niña years and a weakening as a decrease in this magnitude. All three warming patterns generally project weakening across most tropical basins. Over the North Atlantic, ENSO’s influence is uniformly suppressed, with the suppression intensifying from uniform to El Niño–like to La Niña–like warming. However, in the southeastern western North Pacific, both uniform and El Niño–like warming strengthen the ENSO–TCGF linkage, while La Niña–like warming continues to weaken it. These divergent responses arise from pattern-dependent changes in atmospheric heating, which drive Walker circulation anomalies and in turn regulate local large-scale environmental conditions including vertical wind shear, low-level vorticity, and midtropospheric humidity, thereby modulating the ENSO–TCGF relationship. Our results highlight that the spatial patterns of SST warming, not its magnitude, play a pivotal role in modulating future ENSO–TCGF relationships, with implications for regional cyclone risk and seasonal forecasts. Significance Statement Tropical cyclone (TC) genesis is strongly modulated by El Niño–Southern Oscillation (ENSO), which serves as a key predictor for seasonal TC forecasts. However, future patterns in sea surface temperature (SST) warming remain uncertain, and it is unclear how diverse possible SST warming scenarios may influence the ENSO–TC genesis frequency (TCGF) relationship. This study demonstrates that spatial patterns of SST warming—not the magnitude of warming—play a dominant role in shaping future ENSO–TCGF linkages. While ENSO–TCGF relationships generally weaken under all warming scenarios, a notable strengthening (defined here as an increase in the magnitude of the TCGF difference between El Niño and La Niña years) occurs in the southeastern western North Pacific under uniform and El Niño–like warming. These results underscore the importance of considering SST pattern diversity in future projections and in improving seasonal TC prediction under climate change.