Impacts of Tropical North Atlantic SST on Western North Pacific Landfalling Tropical Cyclones

Abstract

This study examines the impacts of tropical North Atlantic (TNA) sea surface temperature anomaly (SSTA) on western North Pacific (WNP) landfalling tropical cyclones (TCs). The authors find that TNA SSTA has significant negative correlations with the frequency of TCs making landfall in China, Vietnam, the Korean Peninsula and Japan, and the entirety of East Asia. TNA SSTA influences the frequency of TC landfalls in these regions by regulating TC genesis location and frequency associated with modulated environmental conditions. During cold TNA SST years, larger low-level relative vorticity and weaker vertical wind shear lead to more TC formations over the South China Sea (SCS) and western Philippine Sea (WPS), and larger low-level relative vorticity, higher midlevel relative humidity, and weaker vertical wind shear result in more TC formations over the eastern part of WNP (EWNP). More TCs forming over different regions are important for more TC landfalls in Vietnam (mainly forming over the SCS and WPS), south China (predominantly forming over the SCS), Taiwan (mostly forming over the WPS), and the Korean Peninsula and Japan (forming over the WPS and EWNP). Tracks of these landfalling TCs basically follow the mean steering flow in spite of different directions of steering flow anomalies in the vicinity. The modulation of large-scale environments by TNA SSTA may be through two possible pathways proposed in previous studies: the Indian Ocean relaying effect and the subtropical eastern Pacific relaying effect. The results of this study suggest that TNA SSTA is a potential predictor for the frequency of TCs making landfall in China, Vietnam, the Korean Peninsula and Japan, and the entirety of East Asia.