Dynamic Factors Dominate the Summer Precipitation Intensity of Atmospheric Rivers Landfalling Eastern China

Atmospheric rivers (ARs), narrow and intense moisture corridors typically extending poleward, significantly shape the hydrometeorological patterns across mid-latitudes. In this study, summer days with AR-related precipitation in eastern China (EC) during 1979−2022 were identified and categorized into six distinct levels based on precipitation intensity percentiles, derived from both the ERA5 and CN05.1 datasets. Results reveal a significant positive correlation between the maximum AR precipitation and maximum integrated water vapor transport (IVT) within each category, while no such correlation exists between mean AR precipitation and mean IVT. As precipitation strengthens, the proportion of areas experiencing precipitation on AR days progressively expands, approaching 100% in the strongest cases. The Sichuan Basin, Northeast China, and coastal South and East China exhibit relatively higher precipitation intensity and efficiency under weak–moderate categories. For moderate−heavy categories, the middle and lower Yangtze River and North China emerge as additional key AR precipitation-affected areas, while the influence on coastal regions significantly decreases. The frequency of AR precipitation days shows a distinct north–south gradient, with hotspots shifting systematically from Northeast to South China as intensity rises. Moisture budget analysis shows that the primary factor controlling AR precipitation intensity is vertical moisture convection, particularly its dynamic component, and zonal advection ranks second. Vertical motion, which governs these processes, is mainly driven by anomalous convergence and divergence linked to the subtropical westerly jet, with topography and atmospheric instabilities further enhancing its impact. These findings may offer valuable insights for future research on AR precipitation and related disasters in China.