冰雹分档方案及成雹机理数值模拟研究

Hail cloud, with powerful updraft，intense spatal and temporal inhomogeneous dynamic and thermal structure. Hail cloud, also has apparently strong interaction between particles in cloud,which have a wide range distribution in size,as well as between micro-macro physical processes. There are different mechanisms of hail formation in hail clouds from different regions, as well as for hail clouds with different type. With respect to general convective precipitation, hail process further needs the cloud model spectral dealt with all types of hydrometeor particles,to study hail formation and growth processes, and the mechanisms of hail formation　from different hail cloud processes. In this study, spectral microphysics of frozen drop and hail particle are introduced into a existing 3-D bin cloud model,with aerosol, droplet, ice crystal, snow and graupel particles already dealt with,to build bin cloud model for hail study. hail clouds with hail particle spectrum observations are selected as study cases,and compares simulation results with observed raindrop size distributions,hail particle spectrums and radar echo datas. New hail cases in the South and North China will be further collected. Based on the numerical simulations, the following issues for different types of hail clouds from different regions, companied with different meteorological and aerosol backgrounds will be studied：（1）the distribution of air-flow field;(2)the distribution and evolutuon of hydrometeor particles in hail clouds;（3）type, size and concentration features of hail embryos; (4)the conversion processes from cloud particles to hail embryos, and that from hail embryos to hail particles;(5)the distribution and evolution of hail particles with different size,especially that with large size.From these studies, to obtain the key physical processes for hail formation and growth,to identify the appropriate occasion and location of hail suppresion and optimize the operational programs of hail suppresion.

雹云上升气流强、动力热力结构时空演变剧烈；云中粒子尺度分布广，不同尺度、相态粒子间及宏微观物理过程相互作用剧烈；不同地域、类型雹云成雹机理存在差异。因此，降雹过程较一般对流降水更需要粒子全分档云模式来描述冰雹形成增长规律，研究不同地域、类型雹云的成雹机理。项目在已对气溶胶、液滴、冰晶、雪和霰分档处理的三维对流云模式中增加冻滴和冰雹分档方案，构建粒子全分档雹云模式。从我国有雹谱观测资料的雹云中选取单体、超级单体、多单体等过程进行数值研究，利用收集的雨滴谱、雹谱及雷达回波等资料验证模式。同时收集我国南北方新的降雹个例。研究不同地域、雹云类型、大气及气溶胶背景：雹云流场结构；云中水凝物粒子分布演变规律；雹胚类型、尺度、浓度；云粒子-雹胚-冰雹间的转化规律；不同尺度尤其是大粒径冰雹的分布演变规律。得出不同雹云中冰雹形成增长的宏微观物理机制，冰雹形成及质量增长最快的时机、部位，优化人工防雹作业方案。

对于我国不同地域冰雹云进行梳理、分类，得到我国不同地域、雹云类型降雹雹谱分布特征。基于冰雹分档方案对不同类型雹云中的冰雹形成增长规律及雹谱分布特征进行数值模拟，研究发现不同类型雹云中冰雹形成增长的微物理机制存在差异，具有不同的冰雹粒子谱分布特征。基于实际冰核参数化方案，研究了不同冰核参数化方案对冰雹云宏微观演变特征及成雹规律的影响，结果表明在不同冰核参数化方案作用下，伴随初始核化冰晶浓度的增加，早期冰雹形成可能受到抑制，而成熟阶段后期冰雹形成增长作用可能加强。同时，当强对流（雹）云强度很强，水汽足够充沛，冰核浓度增多在前期并没有抑制雹胚的形成和增长，而后期因大量冰粒子下落，较早地产生下沉气流，阻碍强上升气流的维持，抑制冰雹继续增长。通过对地面云凝结核（CCN）的连续观测，发现不同季节、不同天气条件及不同能见度CCN活化谱存在显著差异。研究CCN浓度对冰雹物理特性及降雹过程的影响发现，CCN较高时，冰雹更倾向于干增长，冰雹密度减小。随着CCN浓度减小，在较清洁状态下，冰雹更倾向于湿增长，冰雹密度增加。