基于数字全息的云中冰晶微物理参数观测方法  

Observation Method of Microphysical Parameters of Ice Crystals in Cloud Based on Digital Holography

作　　者：杨晨遇 王骏[1] 张川 周浩 杨军胜 岳治国[2] 梁谷[2] 刘晶晶[1] 华灯鑫[1] Yang Chenyu;Wang Jun;Zhang Chuan;Zhou Hao;Yang Junsheng;Yue Zhiguo;Liang Gu;Liu Jingjing;Hua Dengxin(School of Mechanical and Precision Instrument Engineering,Xi'an University of Technology,Xi'an 710048,Shaanxi,China;Center of Weather Modification of Shaanxi Province,Xi'an 710016,Shaanxi,China)

机构地区：[1]西安理工大学机械与精密仪器工程学院,陕西西安710048 [2]陕西省人工影响天气中心,陕西西安710016

出　　处：《光学学报》2024年第6期188-197,共10页Acta Optica Sinica

基　　金：国家自然科学基金(42375126,41975045,52127802)。

摘　　要：冰晶是云滴谱的重要组成部分,其对全球辐射收支平衡、全球气候变化、水文循环、人工影响天气作业等具有重要的影响。目前2~100μm的冰晶与液滴混合相态难以区分,且存在难以提供冰晶微物理参数的瓶颈问题。针对这两个问题,本文基于数字全息理论,利用全域数字图像融合方法、局部亮度梯度方差法和旋转卡壳法,结合固液相粒子圆度概念,实现了云中液滴和冰晶的混合相态识别,在特定圆度阈值下,液滴和冰晶的识别率大于93%;再结合光学图像识别技术,获得冰晶粒子的面积、周长、凸包和最小外接矩形数据;最终利用上述数据获得了冰晶微物理参数。通过在低温云室中的观测实验,获取了板状、枝状和六角冰晶的微物理参数,该方法解决了冰晶观测中的瓶颈问题。此外,通过冰晶采样间隔时间和不同时刻的质心三维坐标和等效直径,还可获得冰晶粒子的三维运动速度与轨迹。该方法对提升数值天气预报精确度,以及人工影响天气作业具有重大意义。Objective As an important component of the cloud droplet spectrum,ice crystals exert important effects on global radiation budget balance,global climate change,hydrological cycle,and weather modification.Due to the limitation of observation means,the understanding about the microphysical characteristics of ice crystal particles is not perfect till now.At present,it is difficult to identify the mixed phase of 2-100μm ice crystals from droplets,and there is a bottleneck to provide microphysical parameters of ice crystals.The lack of sufficient ice crystal detection data can cause large differences in the mean value of ice water paths in different models,especially in mixed-phase clouds.Therefore,we study the microphysical parameters of ice crystals.Methods For these two problems,based on the digital holography theory,we propose to employ the global digital image fusion method,the local Tenengrad variance method,and the rotating caliper method for identifying mixed phase states of droplets and ice crystals in the cloud by combining the roundness concept of solid and liquid particles.Combined with optical image recognition technology,we obtain the area,perimeter,convex hull,and minimum enclosing rectangle data of ice crystals.Finally,the microphysical parameters of ice crystals are acquired by adopting the above data.The microphysical parameters of plate,dendritic and hexagonal ice crystals are obtained by observation experiments in lowtemperature cloud chambers.Results and Discussions Some obvious conclusions can be obtained by adopting the proposed method.1)By leveraging the rotating caliper method and the specific geometric parameter roundness F,the mixed phase identification of droplets and ice crystals in clouds is realized.Under the specific roundness threshold,the recognition rate of droplets and ice crystals is greater than 93%(Fig.8).2)Combined with optical image recognition technology,morphological data(the area,perimeter,convex hull,and minimum enclosing rectangle data)of ice crystal particles are obtaine

关 键 词：数字全息 粒子相态识别 冰晶 粒子速度 

分 类 号：O438.1[机械工程—光学工程]