The Characteristic, Multiscale Dynamic Mechanisms and Impacts of Heavy Precipitation Events in the Yangtze River Valley

Abstract

Heavy precipitation events (HPEs) in the Yangtze River Valley (YRV) pose persistent threats to population safety and infrastructure. This study classifies five population-weighted HPE types (P1–P5) and examines their underlying dynamics using multiscale window transform and canonical energy transfer framework. Each type links to distinct circulation patterns. During 1979–2020, P1 and P2 are associated with Meiyu front systems, with P1 producing stronger precipitation. P2 accounts for 68% of all events, resulting in the greatest population exposure. P3 is driven by landfalling typhoons and represents the second most frequent type. P4 arises from short-wave disturbances that primarily affect northern YRV, whereas P5 is concentrated in the western YRV and influenced by low-vortex systems. Multiscale energy diagnostics show that most HPEs draw energy from the transfer of available potential energy (APE) from background to synoptic circulations, which subsequently convert to kinetic energy (KE). This transfer dominates the maintenance of P1 and P2. In contrast, P3 cases rely more on KE cascades, reflecting their stronger dynamic forcing. P4 and P5 exhibit weaker exchanges and depend more on background circulations. Additionally, future climate projections indicate that warming will amplify convective instability and strengthen APE-to-KE conversions in P1 and P3, but weaken these transfers in P2, P4, and P5. As a result, the currently dominant P2 type is expected to decline, while P1 and P3 become more frequent. By 2100, the population exposed to these type events will increase by more than 20%, posing substantial risks to societal resilience and adaptation.