摘要
利用含有详细微物理过程的一维层状云模式模拟,研究了2002年4月5日冷锋降水性层状云云系中“催化供给”云的微物理结构、降水粒子形成的环节和微物理过程,并从降水形成的环节和云的结构分析人工增雨的条件。结果说明,“催化供给”云具有显著的分层结构:云内高层是冰晶,下层是雪,接下来是霰和过冷云水组成的冰水混合层,最下方是云中暖区的液水层。作为催化云层的冰水层对降水的贡献约25.5%,冰水混合层为31.3%,液水层为43.1%,亦即供给云对降水的贡献约74.4%。具有“催化供给”云结构的层状云降水形成的主要环节是:冰晶通过凝华增长转化成雪,雪撞冻过冷云水、收集冰晶和凝华增长转化形成霰,霰靠撞冻过程、收集雪过程长大,从而形成可以降落到云的暖区融化形成雨水的粒子,它对降水的贡献较大。凝华和撞冻增长过程是冰粒子增长的主要物理过程,也是雨水产生的重要过程。“催化供给”云体系是重要的人工增雨条件,云中水汽对雨水形成的贡献与过冷云水几乎相当,与过冷云水一样,水汽也是人工增雨的重要条件。
The frontal precipitation cloud system is an important seeding object for artificial precipitation and “seeding - feeding” cloud is the typical structure of precipitating cloud in it. Therefore, it is attended in studies of theory and technique of artificial precipitation. Although action mechanism of the “seeding - feeding” in the cloud system has been advanced for a long time, detail of the microphysical processes has still not been understood entirely. The microphysical structure and microphysical processes of precipitation formation in “seeding - feeding” cloud of cold frontal precipitation stratus cloud system occurring on 5 April 2002 in Henan Province are studied by a 1-D stratus cloud numerical model with detail mierophysical processes, and artificial precipitation conditions are analyzed based on links in rainfall formation and the cloud structure. The results indicate that there is remarkable stratified structure in the “seeding - feeding” cloud. The ice crystal layer is located in the upper level, and below it there is the snow layer and mixed ice-water layer consisting of graupel and supercooled water, the liquid water layer is in the warm region of the cloud. It can be shown from the rain water content increase in failing down that raindrops are growing by collection of cloud water in the warm region. The ice - water cloud, as a seeding cloud, make a contribution of 25.50/00 to rainfall, the mixed ice - water layer 31.30/00 and the liquid water layer 43. 1%, i. e. , contribution of the feeding cloud to rainfall is about 74.4%. Besides, 70% of rainfall is from graupel, i. e. , the cold- cloud processes play an important role in rainfall and growth of ice particles in the mixed ice - water layer is very important for precipitation formatiora Main link of precipitation formation in the stratus cloud with “seeding- feeding” cloud structure are as follows; ice crystals is converted into snow by sublimation, and snow is converted into graupel by sublimation, collection of supercooled water and ice crystal. The graupels are grown into big particles, which can melt into rain water as falling to the warm zone, by collecting supercooled water and snow. This process plays an important role in precipitation formation. The sublimation and collecting supercooled water are main growing processes for ice particles and important processes to producing rain water. The rainfall on ground is formed by three ways. first, the rainwater is produced by warm rain processes and increased by collecting cloud water, which has a contribution of 30% 40% for total rainwater; second, the rainwater is from melting of ice particles falling to the warm region and the most of rainwater is formed by ice particle melting. The rainwater amount from the melting is about 50%- 60 % of total rainwater amount; third, the melted ice particles grow continuously by collecting cloud water in the warm region. This process converts the cloud water into rainwater and has a contribution of about 10% for total rainwater amount. In stratus cloud with “seeding - feeding” mechanism, if water content of cloud water is very low in the feeding cloud, there is no high rainfall intensity; similarly, if there is a lack of the seeding action of ice particles from top part of the cloud, the feeding cloud situated in mid-low level also does not produce large rainfall amount. The “seeding- feeding” cloud system is an important structure for artificial precipitation Same as supercooled cloud water, water vapor is also an important condition for artificial precipitation because it and cold water almost have the same contribution to rainwater. Besides, cloud water content in the supercooled region of the feeding cloud is also an important condition for artificial precipitation, but it can be seen from a study of precipitation mechanism that increment of melting ice particles by collecting cloud water is about 10G of total rainwater amount. Therefore, cloud water content and thickness of warm region in the feeding cloud is regarded as factors for artificial precipitation.
出处
《大气科学》
CSCD
北大核心
2005年第6期885-896,共12页
Chinese Journal of Atmospheric Sciences
基金
国家"十五"攻关课题2001BA610A06
国家自然科学基金重点项目40333033
关键词
“催化-供给”云
云粒子形成
降水机制
人工增雨条件
“seeding- feeding” cloud, cloud particle formation, precipitation mechanism, artificial precipitation condition
作者简介
洪延超，男，1948年出生，研究员，主要从事云和降水物理学研究。E-mail：hyc@mail．iap．ac．cn。
