北京地区一次降雪系统大气水凝物输送特征及降雪微物理机制的数值模拟研究

Numerical Simulation Studies of Atmospheric Hydrometeor Transportation Characteristics and Snowfall Microphysical Mechanism during a Snowfall System in Beijing

北京冬季降雪云系存在丰富的可开发利用的云水资源。出于人工增雪研究和充分开发云水资源的需要,文中对北京2019年11月29日发生的年度首场降雪进行了观测,对其资料做了分析和中尺度数值模拟,研究了降雪过程的宏观特征、水凝物输送及降雪的微物理机制。结果表明:影响本次北京降雪的是稳定性层状冷云云系,水凝物主要从北京区域的西边界和南边界输送到区域内,而从东边界和北边界流出,具有西向和南向分量的湿气流是降雪云系水物质的输送通道。降雪云中的水凝物基本全为冰晶和雪,有少量的云水,整层云系都含有非常丰富的水汽并且贯穿整个降雪时段。在冰面过饱和环境中,水汽凝华(Prds)是雪的主要增长过程;其次是云冰增长成雪(Prci)和云冰聚合成雪(Prai)的过程。

There are abundant cloud water resources for development and utilization in the snowfall cloud system in winter in Beijing.For the needs of artificial snow enhancement research and full development of cloud water resources,the first annual snowfall in Beijing was observed on November 29,2019.Data are analyzed,and numerical simulation is carried out.The macro-observation characteristics of the snowfall process are studied,and the atmospheric hydrometeor transportation characteristics and microphysical mechanism of the snowfall are also analyzed through the simulation results.The results show that the stable stratified cold cloud system affects the snowfall in Beijing.Water vapor and water condensate are mainly transported into the region from the western and southern boundaries of the Beijing area and flow out from the eastern and northern boundaries.The cloud hydrometeor transport channel for the snowfall cloud system accompanies a westward and southward component of the moist airflow.The water condensate in the snowfall cloud comprises ice crystals,snow,and a small amount of cloud water.The entire layer of the cloud system contains rich water vapor and runs through the entire snowfall period.In an ice-saturated environment,deposition of snow(Prds)are the main source of the snow,followed by the automatic conversion of cloud ice to snow(Prci)and the accretion of cloud ice by snow(Prai).