区域冷锋降水微物理机制研究

Microphysical Mechanisms of Regional Cold-Front Precipitation

20世纪利用一维层状云模式对2002年4月4～5日河南省冷锋降水过程进行了模拟.数值模拟结果显示,此次冷锋降水属于冷云降水过程,冷锋前后云中主要以冰相粒子为主,云中水质粒自上而下的空间分布依次为冰晶、雪、云水、霰、雨水.冷锋前后,各种水质粒有着不同的含量及数密度,但形成水质粒的主要微物理过程都表现为：冰晶数密度的增加主要依靠核化、繁生,大部分雪主要靠凝华、撞冻过冷云水和冰晶增长,霰的质量增加主要靠撞冻雪、过冷云水和雪自动转化而来,大部分的雨水是由霰融化而来,因而此次冷锋降水机制表现为“水汽-雪-霰-雨水”。

The precipitation on 4, 5 April 2002 in Henan Province was simulated by the one-dimension stratiform cloud numerical model. The results indicate that the precipitation belongs to cold-cloud precipitation; ice-phase particles were the main components in the cold clouds both before and after the front; and the distribution of water particles from top to bottom was ice crystals, snow, cloud water, graupel and rainwater. The content and the number density of these particles in the front of the cold front were different from those behind the front, but the main microphysical mechanisms of particle formation were the same. The increasing of the numerical density of ice crystals depended mainly on nucleation and multiplication; that of snow mostly on the sublimation and accretion of ice crystals and cold cloud water; and the mass increasing of graupel on the accretion of snow and supercooled cloud water and the auto-conversion of snow. Almost all of rainwater came from graupel melting. Therefore, the mechanism of cold-front precipitation was mainly described as ＂vapor-snow-graupel-rain water. ＂