Abstract:Based on the automatic meteorological station data, Doppler radar data and NECP /FNL reanalysis data, the circulation background, trigger and maintenance mechanisms, supercell structure, and cloud microphysical characters of a supercell hailstorm occurred on 13 June 2018 in the central Shandong Province are studied with the WRF model. The study shows that the hailstorm was a supercell hailstorm triggered by the mesoscale convergence line under the background of cold vortex in North China. The suction of the strong divergent flow at the top of the hail cloud was the dynamic instability maintenance mechanism. In the mature stage of the simulated hail cloud, the height of the 0 ℃ level was 4 km, and the echo height of more than 40 dBz reached 12 km; in the flow field, ascending motion was dominated, and there was a motion conversion of ascendingdescendingascending on both sides of the ascending motion, which was conducive to the collision and growth of the hail. The snow crystals were formed by the collision of supercooled cloud water and cloud ice at first, and then transformed into graupel particles by the collision of supercooled water and cloud ice, which provided enough hail embryos for hail formation. Graupel and hail particles, driven by the ascending motion, passed through the supercooled water accumulation zone of the hail cloud repeatedly, which was conducive to their continuous growth and transformation into large hailstones.
