Fine‐Scale Characteristics and Upper‐Level Forcing of Heavy Rainfall Over the Northeastern Tibetan Plateau

Abstract Understanding the mechanisms behind heavy precipitation is crucial for predicting those events. Based on hourly ERA5 reanalysis and rain gauge records, this study investigates the spatiotemporal evolution and anomalous upper‐level circulation of heavy regional rainfall events (RREs) in summer over the southern Qilian Mountains, a key center of heavy rainfall in the northeastern Tibetan Plateau. Two distinct types of heavy RREs are identified, accounting for 73.6% of the total summer rainfall. Type 1 is confined to a relatively local spatial scale and has a shorter duration, with a diurnal peak occurring at 2200 LST, whereas Type 2 exhibits widespread propagation from the northwest to the southeast, with a longer duration and a diurnal peak occurring at 0600 LST. Distinct upper‐level disturbances contribute to the evolution of these two types of events. For Type 1, a positive anomaly in potential vorticity near the tropopause is observed due to the intrusion of high potential vorticity air from the stratosphere, reducing the stability of the lower troposphere. In contrast, Type 2 is characterized by an eastward‐moving warm anomaly, centered at 350 hPa. The upper‐level warm anomaly contributes to upper tropospheric divergence and lower tropospheric water vapor convergence. The upper‐level warm anomaly may result from the northward extension of South Asia High, as well as the warm anomalies in the middle and lower troposphere. The findings of this study enhance the understanding of the impact of upper‐level disturbances on heavy precipitation in the complex terrains of arid and semi‐arid areas.