北京海坨山区低槽降雪云系演变特征的观测研究

The characteristics and evolution of low trough snowfall cloud system in the Haituo mountain，Beijing

中文关键词:  降雪  雪花显微观测  海坨山  北京

英文关键词:Snow  Snowflake micro observation  Haituo mountain  Beijing

中文摘要:

      2019年2月14日在北京海坨山地区出现了一次由低槽云系产成的降雪过程。利用飞机、Ka波段云雷达、微波辐射计、降水粒子谱仪、雪晶显微观测仪等协同观测数据集，分析了此次降雪过程的天气形势、中尺度和微观结构的演变特征。协同观测显示：（1）降雪过程由高空低槽和地面倒槽槽前西南暖湿气流与低层东风回流干冷偏东风共同影响形成，西南风厚度和强度与地面降雪量以及降雪粒子数浓度成正相关。（2）降雪云系为冰云，地面降雪形状主要为片状、枝状和柱状单晶体，冰雪晶的凝华-聚并增长是降雪的主要形成机制。（3）大量枝状雪花的攀附现象出现在地形云爬升阶段，即低层东风回流减弱，转由倒槽槽前西南暖湿气流控制。（4）过冷水的出现与地形抬升有关，地形云爬升期间存在人工增雪潜力。

英文摘要:

      A typical snow case during a low trough controlled weather system was measured in Haituo Mountains of Beijing on 14 February 2019. The observations from aircraft, Ka-band cloud radar, microwave radiometer, precipitation spectrometer and snow shape detector provide a unique dataset, which is used to analyze the evolution of synoptic situation and meso- and microscale structures associated with the snow process. The results are as follows: (1) Snow was formed by the combination of warm moist southwesterly winds in front of the low trough and inverted trough at high levels and cold dry easterly winds in the lower layer. The thickness and strengthen of the southwesterly winds are positively correlated with snowfall and concentration of snow particles. (2) Snow clouds consist of ice particles and the main snow shapes are flake, dendritic and columnar single crystals. The snow formation mechanism mainly involves sublimation and coalescence. (3) Large amounts of dendritic aggregated snowflakes were found in the lifting process of orographic snow clouds. In this situation, the weather was controlled by warm flows coming from the southwest with abundant humidity in front of the inverted trough. (4) The occurrence of supercooled liquid water is related to the lifting by the topography, during which a good potential exists for artificial snow enhancement.