Regional contrasts in short-duration heavy precipitation and associated low-level-jet environments over the Liaohe River Basin

Short-duration heavy precipitation (SDHP) is a major driver of flash flooding and urban waterlogging in the Liaohe River Basin of Northeast China. Here we combine hourly precipitation observations from 3,675 automatic weather stations with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis (ERA5) over seven warm seasons between 2016 and 2024 to examine regional contrasts in SDHP environments associated with low-level jets (LLJs). K-means clustering identifies three frequency-based groups, denoted CP, CPH and HM, representing high-, intermediate- and low-frequency clusters, respectively. CP is concentrated along the southern coast, whereas CPH and HM are spatially mixed, with HM containing a larger proportion of elevated stations. Matching SDHP hours with preceding-hour LLJs shows that LLJs accompany most SDHP occurrences across all three groups, indicating a broadly shared LLJ-associated background. Composite analyses reveal regional contrasts in moisture transport, meridional circulation and thermodynamic structure, although statistically significant departures over the principal precipitation areas are spatially localized. Bayesian-network analyses further indicate broadly shared associations of moisture, low-level shear, instability and LLJ strength with SDHP frequency. The association between diurnal period and SDHP frequency is retained in CP and CPH but not in HM, and appears more evident in CP. Together, these results reveal a common LLJ-associated environmental setting superimposed on regionally varying dynamical and thermodynamic structures.