山地突发性降雨, 绕流和爬流, 局地环流, WRF模拟, 感热和潜热

Studying the basic characteristics of sudden rainfall events in mountainous areas, along with the local circulations induced by dynamic and thermodynamic processes, is of great significance for improving the accuracy and timeliness of forecasting sudden

heavy rainstorms in such environments. This paper investigates two sudden rainfall events in the mountainous region of Mianyang,

China, based on the china multi-source merged precipitation analysis system (CMPAS), black body temperature (TBB) data from the FY-2G satellite, and ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Diagnostic analyses and numerical simulations were conducted using equations representing flow around, up, and over mountains.The results indicate that both sudden torrential rainfall events in mountainous areas occurred under the influence of the western Pacific subtropical high within a weak synoptic-scale environment. The convergence of cold and warm air masses, combined with favorable moisture supply and high-temperature conditions, served as the primary triggers for the rainstorms. Cross-mountain airflow induced by terrain obstruction generated both around and over flow motions. Within the rainfall zone, these processes enhanced vertical ascent and localized vortices. When weak cold air intruded, flow over dominated, and the combined effects of ascending and deflected flows created favorable dynamic conditions for the initiation and intensification of the sudden rainstorms. In contrast, under strong cold air influence, the contributions of around and over flows to heavy rainfall were significantly reduced. The around and over flows within the rainstorm area were coupled with the intensity of precipitation. During the rainfall process, the cessation of surface heat input led to a significant weakening of thermal disturbances near the rainfall area, preventing the formation of local circulation in the western basin, resulting in weakened around and over flows, and the disappearance of the convergence zone, which led to a noticeable reduction in simulated precipitation and the disappearance of the heavy precipitation center. Numerical simulations for both events demonstrated that latent heat played a more critical role than sensible heat in driving precipitation.

sudden rainfall in mountainous, flow around and flow over, local circulation, WRF simulation, sensible heat and latent