Analysis of Extreme Precipitation and its Typical Synoptic Patterns over the Upper Reaches of the Yellow River

The frequency of disasters induced by extreme precipitation (EP) in the upper reaches of the Yellow River Basin (URYR) has increased notably. We conducted a comprehensive investigation into the EP and its associated synoptic patterns in the URYR. The circulations associated with EP events are categorized into three distinct types: Eastward–Moving Cold and Low (Type 1), Westward–Extension Western Pacific Subtropical High (Type 2), and Cut–Off Cyclone (Type 3). By subtracting the climatological state, anomalies in the geopotential height field, wind field, temperature field, and moisture were systematically analyzed for each type. Additionally, the mechanisms driving EP were comprehensively examined using the moisture budget and moist static energy equations. Type 1, the most frequently occurring pattern, is closely linked with a high prevalence of plateau shear and is predominantly associated with negative anomalies in both geopotential height and temperature fields; moisture largely originates from the Bay of Bengal and the Southeast Coast; and the zonal scale of ascending motion is the largest, accompanied by a relatively large area scale of EP. Type 2 is characterized by the most pronounced extreme properties, corresponding to positive anomalies in both geopotential height and temperature fields; moisture is primarily sourced from the Western Pacific Subtropical High, accompanied by the strongest ascending motion dynamics in the northern segment. Type 3, the least frequent pattern, is characterized by an exceptionally deep and persistent Cut–Off Cyclone, with meridional wind components in advecting cold and moist air contributing most to URYR. And the regions with the highest moisture convergence and the most pronounced vertical ascending motion show a strong correlation with the locations of observation stations where the EP events are recorded.