Mechanisms for two types of extreme heavy rainfall in northern China under similar synoptic‐scale background environments

Abstract Extreme heavy‐rainfall events (EHREs) in northern China are a subject of considerable research interest due to their extreme nature and severe impacts. Given the considerable diversity among such events, further case‐study‐based research is imperative for a more comprehensive and mechanistic understanding. This study investigates an EHRE over northern China during 15–16 July 2024, which evolved through two distinct stages – a shear‐line‐dominated stage and a subsequent vortex‐dominated stage – under similar synoptic‐scale background environments. The first stage, featuring a lower‐level shear line and a quasi‐stationary mesoscale convective system (MCS), produced localized, intense rainfall (˜148.3 mm·hour −1 ). The second stage, governed by a mesoscale vortex, resulted in more widespread precipitation with multiple persistent hourly peaks. Diagnostic analyses reveal that vortex development was primarily driven by convergence‐related vertical stretching, while its splitting and dissipation were triggered by divergence‐induced shrinking and horizontal vorticity export, with vertical splitting serving as a key precursor. Lagrangian trajectory analysis further identified marked contrasts in moisture sources: the first stage was dominated by oceanic contributions (eastern Indian Ocean and Bay of Bengal), whereas the second stage saw increased moisture from the Northwest Pacific and distant continents. The considerable differences in convective organization, dynamic triggers, and moisture pathways demonstrate the inadequacy of relying solely on synoptic‐scale predictors. These findings provide new physical insights and practical references for improving the forecasting of EHREs by emphasizing mesoscale process discrimination and moisture trajectory analysis.