Analysis of Heavy Precipitation and its Typical Weather Patterns over the Upper Reaches of the Yellow River

The frequency of disasters induced by heavy precipitation (HP) in the upper reaches of the Yellow River Basin (URYR) has increased notably. This study had further elucidated the structure and interactions of synoptic systems across different pressure levels and quantitatively characterized the anomalous driving factors. Four weather types had been identified: Xinjiang Trough (Type1, constituting 35% of HP), Mongolian Trough (Type2, 14%), Westward–Extension Western Pacific Subtropical High (WPSH) (Type3, 43%), and Cut–Off Cyclone (Type4, 8%). Influenced by the troughs, the moisture anomalies are transported by the southwesterly jet originating from Bay of Bengal low-pressure systems. In Type3, the WPSH and South Asian High demonstrate the greatest zonal expansion and central intensity (reaching 12610 gpm); this type distinguished by maximal moisture and energy, exhibits the most pronounced extreme properties. The most notable characteristic of Type4 is its stability and persistence presented the most favorable dynamic conditions, despite occurring with the lowest frequency. Due to the anomalous evolution of atmospheric circulation, the anomalies in potential vorticity, column-integrated precipitable water, and convective available potential energy increase; negative anomalies in vertical velocity and moisture flux divergence decline dramatically within 12 to 6 hours preceding HP, signaling anomalous moisture convergence coupled with ascending motion. Low-level moisture is impeded and diverted by the TP topography, generating northerly flow along its eastern flank and forming a distinct “moisture corridor”. Orographic uplift introduces pronounced vertical component to the moisture flux vectors and intensifies local circulations, thereby promoting the initiation and organization of mesoscale systems. The vertical moisture advection serves as dominant mechanism driving HP, while zonal or meridional moist enthalpy predominantly contributes to the physical processes driving the ascending motion under different patterns. These findings may offer a scientific basis for the prediction of HP events in the region.