The Impact of Interactions between the El Niño-Southern Oscillation (ENSO) and Its Related Systems on Typhoon Activity in the Northwest Pacific on a Centennial Scale

Abstract This study investigates the correlation between the El Niño-Southern Oscillation (ENSO) and related variables (such as sea surface temperature (SST), radiation, etc.) in the tropical Pacific region over a long timescale from 1884 to 2019, and their impact on typhoon activity in the Northwest Pacific. The research employs methods including composite analysis, complex empirical orthogonal function (CEOF) analysis, self-organizing map (SOM) cluster analysis, and correlation analysis. The findings reveal: (1) When El Niño or La Niña events occur, the variations in the sea surface temperature anomaly (SSTA) and sea level pressure anomaly (SLPA) in the tropical Pacific are not always consistent. Their combined changes significantly influence typhoon activity. Regions with higher SST and lower sea level pressure (SLP) are more prone to typhoon activity. Typhoons originating in the open ocean have a larger variance in their impact on land, compared to those originating near the coast. (2) El Niño years are more conducive to the genesis of typhoons in the open ocean, with increased typhoon activity in the Asian interior, Japan, and the Beibu Gulf, and longer average typhoon paths. Conversely, La Niña years favor coastal typhoon genesis, with increased typhoon activity in northeastern China, the East China Sea, and the southern coastal regions, and shorter average typhoon paths. (3) Near the coast, the correlation between specific humidity and typhoon frequency is stronger than in the open ocean. In the open ocean, the correlation between sea surface downward longwave radiation (SDLR) and typhoon frequency is stronger than near the coast. This is because strong SDLR in the open ocean provides more energy at the sea surface in typhoon genesis regions, thereby promoting typhoon activity. The relationship between average vertical wind shear in large-scale circulation and typhoon activity shows a positive-negative alternating distribution from south to north.