The Poleward Migration of Tropical Cyclolysis in the Western North Pacific

Abstract

Abstract In the context of global climate change, recent studies indicate a poleward migration trend of tropical cyclones (TCs) in the western North Pacific (WNP), while little attention has been paid to the TC cyclolysis (hereafter Lysis). With respect to two different datasets, this study identifies the poleward migration of the annual-mean latitude of TC Lysis during 1979–2018, being more significant for the intensified TCs, although this trend is suppressed by the reduction in the TC frequency over the sea. It is found that the TC migration is more like a poleward translation of the overall movement rather than the expansion of a specific phase’s distance span. Subsequently, the trends of several environmental parameters related to TC development are also analyzed. The large-scale sea surface temperature warming leads to the increase of potential intensity and enhances the possibility of TC poleward migration. Through controlling the TC formation in the eastern WNP tropics, the variations of vertical wind shear and horizontal winds affect TC Lysis latitude, facilitate the TC development environment around East Asia offshore and island chain areas, and steer TCs poleward migration through the southerly wind anomalies in the area north of 30°N. Regarding the cyclonic vorticity in the lower troposphere and the divergence in the upper troposphere, their influence on TC Lysis latitude is mainly by adjusting the numbers of TCs rather than directly interfering with the TC movement process. The present results indicate that the northern WNP coastal region will also become a TC-prone area in the future, which needs to be treated with caution.