中文摘要：

积层混合云是我国的主要降水云系，也是人工影响天气的主要作业对象，从云降水物理的角度来研究云系的形成和发展维系具有重要的意义．基于积层混合云的重要性，本文从个例研究入手，利用中尺度数值模式WRF，模拟2005年5月17～18日发生在我国西南山区（主要以贵州省为主）的积层混合云降水过程．发现这次过程是由对流云并合扩大层化形成的．云系形成以后，云系附近会不断有对流云生成，并在移动过程中并合进入云系，补充云系发展维系所需的含水量和能量，促使云系不断维持．在积层混合云系的内部，对流云和层状云区不断地发生作用．对流云给周围的层状云不断输送含水量和能量，支持着层状云的发展．云系内部两种云相互作用的结果体现在：对流云内的上升气流速度逐渐渐小，层状云的上升气流速度不断维持，总上升气流面积区扩大．对流云的降水量不断减小，而层状云的降水不断维持，带来了大面积持续时间很长的降水．

英文摘要：

The mixture of convective and stratiform clouds is an important precipitation system and also a major object for weather modification studies. Because of the important effect of the mixture, we studied a process on 17 May 2005 by using a cloud-resolving mesoscale model of WRF. The mixture of this process is formed by convections merging, then many new convections will emerge near the cloud system. The new convections will merge into the mixture in moving process, and supply water and energy to the cloud system, so that the mixture system will maintain. Inside the mixture system, convection and stratiform clouds will act on each other. Convections will transport water content and energy to stratiform clouds around. So updraft velocity in convections will turn weaker, but that in stratiform cloud will maintain continuously and the whole area of updraft extends. Precipitation of convection will diminish, while that of stratiform clouds will maintain, so the mixture clouds can bring stronger precipitation in a large area.