Rossby wave-modulated orbital precipitation anomalies in the Asia-Pacific region

Abstract

Abstract Orbital-scale dynamics of Indo-Pacific Warm Pool (IPWP), Earth’s dominant heat and moisture source, exert far-reaching yet incompletely understood influences on global hydroclimate. Here, by synthesizing sedimentary proxies with transient simulations, we identify a coherent, banded precipitation anomaly across the Asia-Pacific region that cannot be explained by regional dynamics alone. We show that seasonal deep convection over the IPWP excites planetary Rossby waves. On orbital timescales, their integrated effects are consistent with precessional forcing, while precession simultaneously modulates the large-scale atmospheric background state that influences their spatial organization. Guided by summer circulation, the Rossby-wave-related responses extend poleward and reorganize large-scale moisture transport and precipitation across the mid- and high-latitudes. The cumulative wave response and background-state modulation provide a robust dynamical linkage between tropical convection and extratropical hydroclimate on orbital timescales. This mechanism offers a physically consistent interpretation for how low-latitude orbital forcing imprints hydroclimate variability across Pan-Asia via planetary-wave dynamics.