Numerical Simulation and the Underlying Mechanism of a Severe Hail‐Producing Convective System in East China

Abstract

AbstractA severe convective system that produced egg‐sized hail in Jiangsu province in eastern China on April 28, 2015 was simulated using a cloud‐resolving Weather Research and Forecasting model with the spectral bin microphysics scheme. The simulation reproduced the two stages of the convective system: the linear convective system (LCS) and the bow echo system (BES) stages. During the LCS stage, the intensity of updrafts was slightly stronger than that in the BES stage, with abundant supercooled water above the −20°C layer, and graupel and hail mainly generated in this period. The microphysical budget analyses and size distribution characteristics of hail were studied within one cell that produced hail during the LCS. It was suggested that hail mainly formed through water‐graupel collision and increased in size by collecting liquid water. Hail particles with smaller diameter were located around the perimeter of the main updrafts, while larger ones were distributed at the left edge of the updrafts. Trajectories and size growth processes of hailstones within the chosen cell were calculated by a three‐dimensional hail growth model, and it was found that hail originated from the middle levels on the east side of the updrafts, and were transformed westward and downward to the lower levels. They continued to ascend along the left edge of the updrafts and experienced one or more up‐down recycles and fell down to the ground on the west side of the updrafts.