NUMERICAL STUDY ON ICE SEEDING IN HAILSTORMS WITH VARIOUS CLOUD BASE TEMPERATURES

The result of the numerical simulation of hailstorms in various regions in China showed thatthe initiation of natural precipitation elements in the strong convective clouds was related with the autoconversion of cloud droplets to raindrops.The hail emby ros were formed mainly through conversion of cloud droplets to graupels in the hail clouds of the colder cloud base,while for the warmer cloud base,they were formed through the conversin of raindrops to graupels.After seeding artificial ice crystals, more hail embryos were formed through conversion of ice crystals to graupels,which competed with the super cooled water.Ice seeding prompted the conversion rate of rain to graupels,reduced the supercooled raindrops and suppressed hailstone growth by accretion.Seeding would also increase the number density of graupels atthe lower part of clouds,shor ten the growing path of precipitation particles.In some cases the hail suppression effect of repeated seeding is better than that of single seeding.