Observed Characteristics and Formation Mechanisms of Record-Low Western North Pacific Tropical Cyclone Landfalls Over China in Summer 2024

Abstract

Summer 2024 observed a record-low tropical cyclone (TC) landfall activity over China, with only two landfalls representing a 59.8% reduction from the 1979–2023 climatological mean. This study investigates the characteristics and underlying mechanisms of this extreme suppression, revealing distinct monthly variations driven by divergent genesis-related factors. In June, no TCs formed, attributable to an anomalously strong and westward-extended western Pacific subtropical high (WPSH) that suppressed monsoon trough-associated convection. July recorded near-normal landfall frequency despite moderately suppressed genesis, as westward-displaced TC formations and southeasterly steering flows favored TC tracks toward southeastern China. In August, extreme landfall suppression (zero landfalls) occurred despite normal genesis frequency, primarily due to a pronounced northward shift in genesis locations (mean latitude: 24.7°N) induced by northeastward-propagating boreal summer intraseasonal oscillation (BSISO)-associated westerly surges, coupled with anomalous steering flows that deflected all TCs away from China. From a seasonal perspective, this suppressed activity was fundamentally driven by the 2023/2024 “double-peaked” El Niño event, characterized by dual warming centers in the eastern Pacific (EP) and central Pacific (CP). The persistent Indian Ocean warming after this event operated via the Indian Ocean capacitor pathway, triggering unprecedented intensification and meridional expansion of the WPSH and producing persistent suppressive large-scale dynamical conditions throughout summer 2024. These findings highlight the critical role of the BSISO and “double-peaked” El Niño events in modulating western North Pacific TC landfall activity.