Rapid intensification of western north pacific tropical cyclones features more concentrated onset for September and slower translation
摘要
Tropical cyclones (TCs) in the Western North Pacific have exhibited pronounced interdecadal changes in rapid intensification (RI) characteristics over 1980–2023. Using best-track and reanalysis data, this study investigates changes in tropical cyclones genesis, rapid intensification onset location, and translation speed, along with their environmental drivers. By comparing two periods, 1980–2001 (P1) and 2002–2023 (P2), we find that, in September, tropical cyclone (TC) genesis shifted southeastward while RI onset locations became more clustered and moved northwestward by about 5 degrees of latitude. During P1, genesis and RI onset locations were spatially close, showing a scattered, zonally oriented distribution between 110 and 160° E. While during P2, most TCs undergo genesis and RI over the warm pool east of the Philippines, as a result of the enhanced oceanic and atmospheric conditions, especially the higher sea surface temperature and increased tropical cyclone heat potential. Additionally, the westward shift of the subtropical high further promotes the southward movement of tropical cyclone formation locations. Influenced by the weakened steering flow, the mean translation speed from RI onset to peak intensity decreased from 6.2 to 5.0 m s−1, implying longer residence over warm waters and enhanced potential for extreme intensification under recent climate conditions. The spatial variability of RI in the western North Pacific is jointly regulated by interannual (ENSO) and decadal (PDO) variability. Frequent La Niña events and a negative PDO phase contributed to a northwestward shift of RI locations, accompanied by a reduction in translation speed during the RI-to-peak stage.