黄河源区冬季冷云催化降雪过程的物理特征研究

Microphysical Characteristics of Cold Cloud Catalytic Snowfall Processes in the Source Region of the Yellow River in Winter

无人机催化撒播具有机动灵活、起降方便、成本低等优势,是潜在的空中水资源开发利用技术.基于2019年冬季在黄河源区开展的无人机播撒试验,利用地基Ka/Ku雷达、微波辐射计、微雨雷达、风廓线雷达等监测设备获得了催化撒播试验过程中云和降水的物理监测数据,分析冬季冷云催化撒播过程中云层和降水的宏观和微物理特征.分析表明:黄河源区无人机有效作业高度位于-5℃高度层(1090~1400m),高空中较强的水平风与上升气流,有利于碘化银核有效混合到云层中进而达到催化效果.试验过程中,降水粒子下落速度(V)增大,大于自然降水场次同等粒径等级下对应的V;撒播试验后雷达反射率因子(Radar reflectivity factor,Z)明显增加,差分反射率因子(Differential Reflectivity Factor,Z_(DR))变化显著,表明催化作业使得粒子形状变化明显;粒子数浓度(Particle number concentration,N(D))、粒径(Particle diameter,D)亦出现增大;Z在0~25dBz的值在各高度层的概率密度(Probability Density,PD)增加,在无人机撒播高度以下区域增加最显著;大气积分液态水含量(Integrated Liquid Water Content,LWC)增加0.166mm、积分水汽含量(Integrated Moisture Content,MC)增加0.226cm、可降水量(Precipitable Water Vapor,PWV)增加0.09cm.该研究构建的地基综合气象监测体系可以定量评估无人机作业全过程中云物理参量变化、识别撒播目标云层,对高原高寒、低空气密度等气象条件下开展无人机精准撒播提供了可借鉴的实践案例.

UAV(Unmanned aerial vehicle)catalytic spreading is a potential technology for air-water resources development and utilization,with the advantages of flexibility,easy takeoff and landing,and low cost.Based on the UAV seeding experiment conducted in the source region of the Yellow River(SRYR)in winter 2019,the physical monitoring data of clouds and precipitation during the catalytic seeding test were obtained using ground-based Ka/Ku radar,microwave radiometer,micro-rain radar,raindrop spectrometer,and wind profile radar to analyze the microphysical characteristics of clouds and precipitation during the catalytic seeding of cold clouds.The analysis shows that the effective operating altitude of the UAV in SRYR is located in the-5℃altitude layer(1090~1400 m),and the stronger horizontal wind and updraft in the air are conducive to the effective mixing of AgI nuclei into the cloud layer to achieve the catalytic effect.The falling velocity(V)of precipitation particles increased,which was larger than the natural precipitation process under the same particle size class.The radar reflectivity factor(Z)increased distinctly after the experiment,and the differential reflectivity factor(Z_(DR))changed significantly,indicating that the catalytic operation caused significant changes in particle shape.Particle number concentration(N(D)),particle diameter(D)also appear to increase.Probability Density(PD)of Z values from 0 to 25 dBz increased at all height levels,with the greatest increase below the UAV dispersal height.The integrated liquid water content(LWC)increased by 0.166 mm,the integrated moisture content(MC)increased by 0.226 cm,and the precipitable water vapor(PWV)increased by 0.09 cm.The ground-based comprehensive meteorological monitoring system constructed in this study can quantitatively assess the changes of cloud physical parameters during the UAV operation process,and provide a practical case for carrying out precise UAV dispersal under typical meteorological conditions in SRYR.