摘要
观测事实表明,对流云中分布着许多不同大小的云泡,本文根据这一事实讨论有云泡结构的对流云中降水粒子形成的问题。我们考虑在云泡中的含水量和垂直气流均比云泡外的云中的值大,因此这是一个含水量和垂直气流同时起伏条件下滴在云中随机生长的模式。根据滴在云中碰併增长的公式,我们推得一个重要的关系:即对于任何滴同样的半径增量,通过云泡所需移动的距离要比在云泡外的云中所需移动的距离少,而这个距离的差值仅与云泡的特性有关,与滴的初始大小无关,因此滴在云中经过若干云泡的生长就由一个排列问题转变为组合问题,这就便于我们讨论摘随机穿过若干云泡的生长。计算结果表明,有云泡结构的云中,比较薄的云就可以形成较大的水滴或冰雹,或者说降低了形成降水对云厚的要求。本文还计算了云泡特征量对降水形成的影响。
The formation of precipitation in convective cloud with cell structure is investegated,based on the fact that a cloud consists of a great deal of cells in different phases.Considering that water content and speed of updraft in the cloud cells are larger than that in their environments,a cloud model in which droplets grow up by stochastic coalescence under the condition of srmultaneous fluctuation in water content and updraft is designed.According to the growth of precipitation particles by coalescence in clouds,a relationship between the droplet growth and its displacement in the cloud with cells is obtained and,we have also discussed the size distribution of precipitation particles after they have passed through the convective cells at random.We have calculated the formation of rain and hail in different conditions.It can be shown from the spectrum of precipitation obtained when the above behavours are considered that larger precipitation particles could be produced in shallow cloud in this case compared with the same situation(e.g.water content and updraft)in which no cells exist.We have also calculated the effect of the various parameters of the cells on the formation of precipitation,and found that the more the flucluation is,the larger the precipitation will be.The results calculated show that the rainfall and hailfall in the model fit to realistic state.
作者
徐华英
李桂忱
Xu Hua-ying;Li Gui-chen(Institute of Atmospheric Physics,Academia sinica)
出处
《气象学报》
1980年第3期260-268,共9页
Acta Meteorologica Sinica
