中文摘要：

霰和冻滴是深对流降水的主要来源。由于二者密度差异造成的不同下落末速度必然会导致云微物理过程的变化以及降水时空分布的改变。我们在以色列特拉维夫大学二维轴对称对流云全分档模式的基础上,将水成物粒子从34档增加到40档,修改了霰和雪的密度,加入冻滴分档处理的微物理过程,发展了一个包括液滴、冰晶、雪、霰和冻滴更为详细的云微物理分档模式。利用改进后的模式模拟了一次理想的强对流天气过程,分析了改进模式与原模式模拟的云微物理量场以及水成物粒子的时空分布特征,模拟结果表明：（1）由于冻滴的产生,较大的下落末速度导致在云内-3°C至-8°C较早地出现了冻滴,并造成了大量的冰晶繁生。（2）冻滴形成前期,液态水中心区域位于垂直上升速度大值中心上方,形成液态水累积区;冻滴形成期,液态水累积区位于0°C层以上,雨滴冻结生成冻滴,霰与半径大于100μm的液滴碰并生成冻滴;冻滴增长期,在垂直上升气流的支撑下,冻滴碰并过冷水增长,导致冻滴含量增大,液态水含量减小。因此,改进模式能较好的模拟冻滴的形成过程,可以将该分档处理的微物理方案耦合到三维WRF（Weather Research and Forecasting model）模式中,更深入地研究强雷暴风切变在冰雹生成过程中的作用。

英文摘要：

Graupel and frozen drops are the main source of deep convective precipitation. The terminal falling velocity of graupel and frozen drops are different because of the difference between their densities. As a result, cloudmicrophysical processes and the temporal and spatial distribution of precipitation will change. Based on the two-dimensional axisymmetric convective cloud model developed by Tel Aviv University in Israel with detailed treatments of both the warm and cold microphysical processes, the authors increased the bins of hydrometeors from 34 to 40 and modified the graupel and snow densities and developed a bin microphysical model that includes water drops, ice crystals, snow, graupel, and ice pellets. The authors used the improved model to simulate an ideal case of severe convective cloud and analyzed the characteristics of the dynamical fields and hydrometeor distributions. Results of the present study were compared with simulations by the original model. The results showed that：（1） Ice pellets can produce a large amount of ice crystals due to their high terminal velocities, which results in the falling of ice pellets into the ice multiplication zone that is determined by the temperature and concentration of cloud droplets;（2） there is a liquid water accumulation zone before the ice pellet formation, because the maximum area of liquid water is located above the maximum vertical velocity zone. At the stage of ice pellet formation, the liquid water accumulation zone is above the level of 0°C. The ice pellets are formed by water drop freezing and graupel riming with the water drop radius greater than 100 μm. At the stage of ice pellet growth, the ice pellets grow due to the accretion of supercooled water, leading to ice pellet water content increase and liquid water content decrease. The modeling results showed that the improved model could successfully simulate the ice pellet formation process. The improved spectral microphysical scheme will be coupled into the WRF（Weather Research and Forecas