第二届未来大气科学论坛

This study finds season-dependent modulation of the Pacific Meridional Mode (PMM) on landfalling tropical cyclone (TC) frequency (LTF) in East Asia. The correlations between PMM and LTF are significant in Southeast Asia (SEA) during January–March (JFM) and October–December (OND) as well as in Northeast Asia (NEA) during July–September (JAS), while insignificant in any subregion during April–June (AMJ). Quantitative analyses reveal that the basin-wide TC genesis frequency (BF) effect is the primary contributor to LTF anomalies in SEA during JFM and OND, while a combination of BF and the preferable track effect dominates in NEA during JAS. The seasonality arises from the combined impact of PMM on both TC genesis frequency and steering flow. During the positive PMM phase in JFM and OND, enhanced genesis in the main development region (MDR), coinciding with easterly/southeasterly flow, favors TC landfalls in SEA. During JAS, TC genesis shifts northward within the MDR, and southeasterly steering flow anomalies on the north flank of the PMM-induced anomalous cyclone favor TC landfalls in NEA. The insignificant impact of PMM on TC landfalls during AMJ is mainly due to insignificant impact of PMM on BF. The seasonal variations of atmospheric circulation patterns are driven by the westward extension of the PMM-induced anomalous cyclone associated with the Gill-type Rossby wave response across the seasons. This shift is modulated by the seasonal evolution of the PMM-related sea surface temperature warm anomalies in the eastern North Pacific and cold anomalies in the tropical eastern Pacific.
 

tropical cyclone landfalls,Pacific Meridional Mode,Seasonal variability