Enhanced Influence of the North Pacific Meridional Mode on the Western North Pacific Tropical Cyclones in a Warming Climate

Abstract

Western North Pacific (WNP) tropical cyclone (TC) activity is strongly modulated by the North Pacific Meridional Mode (NPMM), yet how this influence responds to global warming remains unclear. Using high-resolution atmosphere-only simulations that reproduce the observed NPMM-related environmental and TC responses, we show that global warming strengthens and reshapes the influence of the NPMM on TC genesis and tracks through an amplified tropical Pacific atmospheric response. Increased sensitivity of atmospheric convection to NPMMrelated sea surface temperature anomalies enhances the convective response over the tropical central Pacific, strengthening low-level cyclonic vorticity and increasing mid-tropospheric moisture over the southeastern WNP, thereby favoring TC genesis. Meanwhile, preferential strengthening of the southern portion of the NPMM-induced easterly steering flow directs TC activity and landfalls toward lower latitudes. These results demonstrate that global warming can reshape regional TC risk by strengthening the influence of the NPMM on TC genesis and subsequent movement.