摘要:本文利用“太行山东麓人工增雨防雹作业技术试验”的飞机和地面雷达观测数据，重点研究分析了2018年5月21日一次典型西风槽天气系统影响下的层状云微物理特征。结果表明，?5°C层的过冷水含量低于0.05 g m?3，冰粒子数浓度量级101～102 L?1。冰粒子数浓度高值区主要以针状和柱状冰晶为主。这可能低层是Hallett-Mossop机制和其他冰晶繁生机制共同作用下所产生的冰晶碎片在冰面过饱和条件下凝华增长所形成的。冰粒子数浓度低值区的冰晶形状基本以片状或枝状为主。?5°C层的冰雪晶增长主要以凝华和聚并增长为主，凇附过程很弱。零度层附近云水含量峰值区的液态水占比达到70%以上。云水含量峰值区的粒子主要以直径10～50 μm的云滴为主，伴随着少量聚合状冰晶。零度层其他区域的过冷水含量维持在0.05 g m?3左右，冰晶形态主要以聚合状、凇附状及霰粒子为主。液水层则主要以球形液滴及半融化状态的冰粒子为主。垂直探测表明：零度层以上的冰雪晶数浓度呈现随高度递增的趋势。在发展稳定的层状云内，混合层的过冷水含量很低，冰粒子主要通过凝华和聚并过程增长，云体冰晶化程度较高。而在发展较为旺盛的层状云区里过冷水含量也较高，大量液滴的存在也表明混合层冰-液相之间的转化不充分。不同温度层的粒子谱显示，冷水含量高值区的冰粒子平均浓度比过冷水低值区高，但平均直径比过冷水低值区小。
关键词:太行山东麓/
层状云/
云微物理/
降水机制
Abstract:Based on the observation data obtained by the “Rainfall Enhancement and Hail Suppression Project on the Eastern Side of Taihang Mountains” in this paper, we analyze the microphysical characteristics of the stratiform cloud induced by the upper-level westerly trough on May 21, 2018. The results indicate that the supercooled liquid water content in the ?5°C layer is less than 0.05 g m?3, and the concentrations of supercooled cloud droplets range from 10–102 L?1. Needle-like and columnar ice crystals are often observed in regions with high number concentrations of ice crystals, which may be related to ice crystal fragments produced by the Hallett–Mossop mechanism and other mechanisms, which are then deposited under super-saturated ice conditions. Ice crystal habits are predominantly planar and dendritic in regions with low ice-crystal number concentrations. Ice and snow crystals mainly grow via deposition and coalescence processes, with a weak rimming process. The liquid water content accounts for more than 70% in regions with a peak cloud water content near the 0°C layer. These particles are mainly cloud droplets with diameters ranging from 10 μm to 50 μm, accompanied by a few aggregates. The supercooled water content is about 0.05 g m?3 in other regions near the 0°C layer, with the ice crystal habits being predominantly aggregates, rimed snow, and graupel. Most of the particles are spherical droplets and melting ice crystals in the liquid water layer. Vertical observations indicate that the ice- and snow-crystal number concentrations increase with height above the 0°C layer. The supercooled-liquid-water content of the mixed layer is much lower in a stable stratiform cloud. Most particles mainly grow by deposition and coalescence, and the degree of ice crystallization is much higher. The existence of liquid droplets indicates that the transformation between the liquid and ice phases is not sufficient in strongly developed stratiform cloud regions where supercooled liquid water is relatively abundant. The particle size distributions at different temperature levels indicate that the average number concentration of ice particles in regions with an abundant supercooled-liquid-water content is higher than those with a low supercooled-liquid-water content. However, the average diameter of ice particles in regions with low supercooled-liquid-water content is larger.
Key words:Eastern side of Taihang Mountain/
Stratiform cloud/
Cloud microphysics/
Precipitation mechanism
PDF全文下载地址:
http://www.iapjournals.ac.cn/dqkx/article/exportPdf?id=62776a18-28be-4f45-8455-c51826cabbb4
