CHARACTERISTICS OF THE RAINDROP SIZE DISTRIBUTION IN A SQUALL LINE MEASURED BY TWO-DIMENSIONAL VIDEO DISDROMETER IN GUANGDONG
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摘要: 利用3台二维视频雨滴谱仪(2DVD)、广州S波段双偏振雷达以及C-FMCW雷达资料，分析广东地区2017年5月8日一次飑线过程不同降水部位的雨滴谱特征。根据雨强随时间变化，区分对流降水区，同时以对流降水区为分界线，将此次飑线过程划分为飑线前部、飑线中部和飑线后部。结果表明，飑线不同降水部位雨滴谱特征存在明显的差别。飑线前部，粒子谱分布变化剧烈，中小粒径的粒子居多，粒子数浓度较飑线中部偏低；飑线中部，粒子分布较分散，中等粒子比重较高，粒子数浓度最高，雨强的增加主要与雨滴数浓度有关；飑线后部，降水粒子分布较集中，且以高浓度中小粒子为主。另外，还研究了μ-Λ关系和Z-R关系。μ-Λ之间存在较好的二项式关系；不同降水部位Z-R关系差异较大，分别为Z=8.94R2.70、Z=526.98R1.22和Z=467.56R1.42。飑线不同部位雨滴谱演变特征存在一些明显差别，同时，同一部位不同空间位置也存在着一定的差异。Abstract: Temporal evolution and spatial variations of the characteristics of raindrop size distribution (DSD) in a squall line in Guangdong on May 8, 2017 are analyzed using data from three two-dimensional video disdrometers (2DVD) at Longmen Field Experiment Base on Cloud Physics, China Meteorological Administration, Guangzhou S-band Polarimetric Weather Radar and C-band Frequency Modulation Continuous Wave (C-FMCW) from Chinese Academy of Meteorological Sciences. This squall line is divided into leading edge, convective subject and trailing edge based on radar reflectivity and rain rate. Results show that, compared with the DSDs in the convective subject, the DSDs in the leading edge are characterized by a higher concentration of midsize and small drops, and a lower drop number concentration; in the convective subject, the concentration of raindrop within each size range is the highest, and the enhanced changes of rainfall are related to the raindrop number concentration; in the trailing edge, the DSDs are characterized by narrower and smoother spectra, and a higher concentration of midsize and small drops. Statistical characteristics of the Z-R and μ-Λ relationship are studied. The Z-R relationship of leading edge, convective subject and trailing edge is Z=8.94R2.70, Z=526.98R1.22 and Z=467.56R1.42, respectively. DSDs in different parts of a squall line have some obvious differences, while imparity can also be found in different spatial position within the same part of a squall line.
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图 3 LM站雨滴谱参数以及偏振参数随时间变化
a.雨滴谱；b.雨强；c.水平反射率因子；d.雨滴质量加权直径；e.新增差分反射率；f.粒子数浓度。黑色实线为2DVD观测结果；蓝色叉号为双偏振雷达反演结果。
表 1 C-FMCW垂直探测雷达系统主要技术参数
序号 参数 指标 1 工作频率 5 530 MHz±3 MHz/±3.5 MHz 2 探测方式 固定垂直指向探测 3 探测量程 0.015~24 km 4 重复周期 600 μs、700 μs 5 扫描带宽 6MHz±3 MHz/±3.5MHz 6 时间分辨率 3 s 7 距离库长、库数 库长：15 m、30 m，库数：800、500 8 探测能力 15 km高度处探测能力低于-20 dBZ 9 天线型式 收发分置、抛物面 10 天线增益 ≥35 dB 11 波束宽度 ≤2.6 ° 12 发射功率 ≥150 W 13 接收通道动态范围 ≥82 dB 14 信号处理 二次FFT 15 数据输出 功率谱密度分布、谱参数 
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表 2 广州S波段双偏振雷达主要数据参数
序号 项目天线系统 参数 序号 项目接收机 参数 1 形状 旋转抛物面 12 最小可测功率 ≤-109 dBm(1.57 μs) 2 直径 8.5 m 13 噪声系数 ≤4 dB 3 波瓣宽度 ≤1 °(3 dB) 14 动态范围 ≥85 dB 4 天线增益 ≥44 dB 15 分辨率 250~1 000 m探测精度 5 天线方向 水平/垂直极化波束主轴方向差≤0.1 ° 16 强度Z ≤1 dB 6 双通道发射机 ≥30 dB 17 速度V/谱宽W ≤1 m/s 7 工作频率 2 885 MHz 18 差分反射率因子ZDR ≤0.2 dB 8 峰值功率 ≥650 kW 19 差分传播相移ΦDP ≤0.2 ° 9 脉冲宽度 1.57 μs，4.7 μs 20 差分传播相移率KDP ≤0.2 °/km 10 脉冲重复频率 322~1 304 Hz 21 相关系数CC ≤0.01 11 工作模式 收发体制
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表 3 不同站点不同降水部位雨滴谱参数以及偏振参数平均值
站点 阶段 样本个数/min R/(mm/h) ZH/dB
Z2DVD/S-PolZDR/dB2
DVD/Dm/mm
2DVD/lgNw/(mm-1·m-3)
2DVD/S-PolLM LP 28 4.32 30.00/34.40 0.95/1.77 2.02/2.05 2.63/3.07 CP 37 19.42 42.99/40.35 1.32/1.68 1.99/2.03 3.60/3.63 TP 228 3.34 32.31/32.39 0.86/0.85 1.62/1.62 3.23/3.70 FG LP 12 2.31 25.63/24.00 0.55/0.46 1.43/1.36 3.09/3.46 CP 65 35.17 44.87/45.08 1.20/1.50 1.83/1.96 4.02/4.26 TP 275 2.94 31.54/30.29 0.80/0.89 1.53/1.63 3.33/3.54 XF LP 23 1.89 25.32/23.83 0.57/0.46 1.74/1.39 2.70/3.41 CP 24 20.57 40.33/42.30 1.02/1.01 1.37/1.58 4.41/4.52 TP 244 2.57 31.03/32.46 0.85/0.76 1.65/1.53 3.10/3.43
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