不同云底温度雹云成雹机制及其引晶催化的数值研究

用二维准弹性冰雹云模式模拟了中国不同地区的冰雹云的成雹机制和人工引晶催化的效果，结果表明：强对流云中自然初始降水元的形成主要同云雨自动转化相关；云底温度较低的冰雹云的雹胚形成以云霰转化过程为主，暖云底的雹云则以雨霰转化为主。人工引晶的作用有三：（１）加强云中冰霰转化过程，雹胚过多争食防雹；（２）促进雨霰转化过程，使雹胚浓度增加，并且减少过冷雨滴，抑制冰雹碰冻过冷雨滴的增长；（３）使云的下部霰量增加，降低降水粒子的增长轨迹，阻碍霰雹的增长。多次催化有时比一次大剂量催化的防雹增雨效果好。

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.