Numerical Simulation of the Accumulation Zones and Hail Growth Trajectories in Hailstorms

A three-dimensional hailstorm model and a three-dimensional Lagrange hail growth model were used to do further study of a hailstorm occurring in Xunyi, Shaanxi Province, on 28 July 1997, which was found out that there existed an accumulation zone in the storm in earlier researches. The modeling results showed that：(1) embryos were formed in the accumulation zone, and the accumulation zone was also the area where embryos accreted in their early stages, however, it was not the main growth area of these embryos.(2) Only when there existed millimeter-sized embryos, can large hailstones form. Moreover, the larger the initial size of particles was, the larger the final size of the hails got and more large stones formed.(3) The trajectories of large hailstones in each experiment presented a simple down-up-down manner, and interestingly, the motion of larger embryos showed some similarity to the growth of hails in classical supercell, however, embryos of classical supercell started from a zone called “embryo curtain”.