A STUDY ON NUMERICAL SIMULATION OF CLOUD MERGERS AND INTERACTIONS

A two-dimensional, time-dependent and warm cumulus cloud model has been used to investigate problems concerning cloud merger and interaction. The results of numerical experiment show: (ⅰ) Two clouds formed at the same time have influence on each other at a shorter distance;on one hand, it is possible that they merge with equal intensity, and on the other, it is impossible that they merge with unequal intensity;in case of quite different intensities the weak cloud is depressed and the strong cloud accretes. (ⅱ) Two clouds, developing with timing difference at a shorter distance and in the same growth stages, may merge. (ⅲ) The merged cloud develops more violently than the unmerged and produces more rainfall. (ⅳ) Cloud merger results from the action of a horizontal pressure gradient accompanied with a circulation field in the lower layer of clouds.     

THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF THE EFFECTS OF ICE PHASE PROCESSES ON EVOLUTION OF CONVECTIVE STORMS

The numerical experiments on sensitivity of two types of convective storms to ice phasemicrophysical processes have been made by using a fully elastic three-dimensional cloud mod-el with a more detailed ice phase parameterization scheme. The simulations show that, ingeneral, inclusion of ice phase processes in the model leads to more intensive modelingstorms--the total latent heat released and the total precipitation increase obviously, the cloudtop rises, and the maximum ground precipitation rate is reached earlier. These effects of icephase processes can be much more significant in some relatively cold environments, in whichthey even modify the dynamic structures and life cycle of simulating storms. The mecha-nisms and favourable conditions of ice phase influences on storms are also discussed.     

冰相过程在积云发展中的作用的三维数值模拟研究

本文采用一个具有较详细冰相过程参数化的完全弹性三维积云数值模式分别作了两种不同类型积云对冰相微物理过程敏感性数值实验。模拟结果表明:模式中加入冰相微物理过程一般使模拟积云更加强盛,总释放潜热和总降水均有明显增大,云顶抬高,地面雨强峰值也提前出现。而在较冷的环境场中,冰相作用变得十分突出,甚至可以引起风暴动力结构和生命史的改变。文中还对冰相作用原理以及条件进行了探讨。     

积云并合及相互影响的数值模拟研究

本文采用二维暖积云模式研究了积云之间的并合及相互影响问题。计算结果表明:同时形成的两块云只有相距较近时才有相互影响,若两云的强度相近可能发生并合,若两云的强度相差较大时,弱云受到抑制,而强云得以增强;非同时形成的云只有在相距较近,且都处于发展阶段时才相互影响;并合云比单独云发展强烈,降水量也大;云的并合是云下层水平气压场及两块云环流流场共同作用的结果。