Potential Stability Features and Topographic Sensitivity Simulation for a Rainstorm Process over the Southern Slope of the Tianshan Mountains, China

The rainstorm that occurred during September 9–10 along the southern slope of the Tianshan Mountains was numerically simulated using the weather research forecast model. The European Meteorological Center ERA5 0.25°×0.25° reanalysis data and precipitation data from the CMORPH satellite were used for this simulation. The potential instability features were analyzed, and the influence of different scales of topography perturbations on the variation of potential instability was examined using a topographic sensitivity test and terrain-following tendency equation of potential stability. The study yielded the following results: (1) Before rainfall, the lower atmosphere exhibited potential instability. However, following the release of unstable energy, the lower atmosphere tended toward stability. (2) The potential divergence term, which was primarily caused by flow-over wind, was the main forcing term in the tendency equation of potential stability. The dominant factor in the flow-over potential divergence was the vertical shear of meridional flow-over wind combined with the meridional gradient of the generalized potential temperature. During the rainstorms, the development of potential instability was influenced by changes in the vertical shear of the meridional flow-over wind and the meridional gradient of the generalized potential temperature due to topography perturbations. These changes contributed to the onset of the rainstorm. The insights gained from this study can help enhance the rainstorm forecast accuracy in Xinjiang.