Escalating Extreme River Discharge Events Driven by Precipitation Changes in the Yangtze River Basin

Extreme river discharge events (ERDEs) directly induce catastrophic floods, posing severe threats to human life and infrastructure. Understanding the precipitation patterns that precede ERDEs is critical for identifying early flood warnings. This study investigated the spatiotemporal characteristics of 3-hourly ERDEs across the Yangtze River Basin (YRB) from 2000 to 2019. A Random Forest model was employed to explore the nonlinear relationships between the cumulative precipitation in local/upstream regions and the number of ERDEs, aiming to identify precipitation patterns and the associated atmospheric processes. The results reveal that ERDEs predominantly occurred in the upper reaches of the eastern Tibetan Plateau and the middle to lower YRB, spanning from March to November, with a peak in July. A significant increasing trend in the occurrence of ERDEs was observed over the 20 years in the YRB. In the eastern Tibetan Plateau and the Dongting Lake Plain, ERDEs were primarily affected by upstream precipitation, associated with the plateau vortex and backwards-tilting trough. In contrast, ERDEs in the western Sichuan Basin and Poyang Lake Plain were mainly driven by local precipitation, linked to the forward-tilting trough and Jianghuai cyclone. Furthermore, regions such as the western Sichuan Plateau, central-eastern Sichuan Basin, Wushan Mountain range, and lower Yangtze River Plain were influenced by both upstream and local precipitation, which were attributed to the westerly trough, southwest vortex, double-vortex, and convective system on the edge of the Northwestern Pacific Subtropical High, respectively. This study presents a novel perspective on identifying early warning signals of flood risk across YRB.