摘要
在播撒防雹中，如何实现人工雹胚与自然雹胚的增长竞争是决定防雹效果的关键，这实质上也是雹云物理的关键课题。经过对强对流（雹）云的流场特征和相应的过冷水场配置的综合分析和数值模拟研究，发现：（１）由于雹云流场的对流性，其中必然存在着一个主上升气流区和相对于云体的水平风速零的区域，它在垂直剖面上，可呈现出一条零线，可长大成冰雹的水凝物粒子是绕零线循环运行增长的，并逐步进入主上升气流区；（２）在雹云中存在着冰雹“穴道”，它位于主上升气流区边侧及零线下的入流区，其体积约为雹云总体的６％或更小，不论自然雹胚或是人工雹胚，只要进入“穴道”都经历着循环运行增长，其轨迹是相互交叉的，因而可以实现平等“竞争”；（３）“穴道”的存在和位置由流场特征决定，运行轨迹的基本形态也由流场决定，而粒子增长率及运行路径的长短由“穴道”内的过冷水场（过冷度和量）决定。
In the 'beneficial competition' hypotheses, which is most promising for the hail- suppression, there is a key problem: how to realize the competition between the natural embryo and artificial one in growth of them by depletion of super-cold liquid water existed in cloud. In fact, it is not only a key to the principle of hail-suppression but also to the physics of hailstorm. With the analysis of the airflow pattern and the studies of simulation for hailstorm and hailstone's growth-travel trajectories, it is found that: (1) Due to the strong convective airflow of hailstorm there must be a core of main-updraft (MUD) and an area by the core of MUD in which the horizontal wind-speed relative to hailstorm equals zero. In the vertical section, there is a zero-line from the edge to core of MUD. Below this line wind blows towards the core, and upon this line wind blows away. The growth-travel trajectories of cloud particles are rotating by this line and can enter the core of MUD circle by circle while forming hailstones. (2) In hailstorm there is a ' cave channel' (CC), whose location is close to the core of MUD and below the zero area. Its volume is about 6% or even smaller of total of hailstorms. The region of embryo formation is in the entrance-end of CC, and the region of hail formation is in the exit-end of CC close to or in the core. Once the particle enters CC, it cannot escape the attraction of CC, just like a trap, until it becomes large stone and falls down from exit-end. As long as the artificial particles are seeded in CC and their trajectores may cross with natural ones, the u beneficial competition' between the natural and the artificial embryos can be realized equally. (3) The existence of CC and its location depend on the airflow, and the rate of hailstone's growth and the length of trajectories depend on the field of super-cold hydrometeor.
出处
《大气科学》
CSCD
北大核心
2001年第2期277-288,共12页
Chinese Journal of Atmospheric Sciences
基金
河北省"九五"重大科技攻关项目!(96-95-12-3)资助
