Abstract:In this study conducted a statistical analysis of five autumn (September-October) hail weather events that occurred in the Yantai region of northern Shandong Peninsula since 2006, based on high and low altitude observation data, Yantai radar echo data, and reanalysis data from the fifth-generation European Center for Medium-Range Weather Forecasts (ERA5). The study revealed that all five autumn hail events occurred in favorable atmospheric conditions characterized by the presence of upper-level cold vortices, shear lines and jet stream convergence, as well as matching surface convergence lines. Prior to hail formation, the difference between Convective Available Potential Energy (CAPE) and Convective Inhibition Energy (CIN) exceeded 724.3 J/kg; The temperature difference between 850 hPa and 500 hPa was greater than or equal to approximately 25°C;The height difference between the 0℃ and -20℃ levels was greater than approximately 2900 m;The vertical wind shear between 0-6 km exceeded approximately 11.1 m/s. In the region affected by hail, there is a significant upward motion between 400 hPa and 800 hPa, with vertical velocities exceeding -1.0 Pa/s, and strong unstable energy, providing certain dynamic conditions for hail formation. In the one to two volume scans prior to the occurrence of hail, the radar storm parameters exhibit an upward trend except for the possibility of a decrease in the height of the storm and echo top. The vertical liquid water content and vertical liquid water content density both reached 37 kg/m2 and 4.4 g/m3, with an increment of 11 kg/m2 and 1.3 g/m3. Large hailstones require an accumulation exceeding 48 kg/m2 and 5.4 g/m3.
