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Ka/Ku双波段云雷达反演空气垂直运动速度和雨滴谱方法研究及初步应用

刘黎平 张扬 丁晗

刘黎平, 张扬, 丁晗. 2021. Ka/Ku双波段云雷达反演空气垂直运动速度和雨滴谱方法研究及初步应用[J]. 大气科学, 45(5): 1−15 doi: 10.3878/j.issn.1006-9895.2104.20200
引用本文: 刘黎平, 张扬, 丁晗. 2021. Ka/Ku双波段云雷达反演空气垂直运动速度和雨滴谱方法研究及初步应用[J]. 大气科学, 45(5): 1−15 doi: 10.3878/j.issn.1006-9895.2104.20200
LIU Liping, ZHANG Yang, Ding han. 2021. Vertical Air Motion and Raindrop Size Distribution Retrieval Using a Ka/Ku Dual-Wavelength Cloud Radar and Its Preliminary Application [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 45(5): 1−15 doi: 10.3878/j.issn.1006-9895.2104.20200
Citation: LIU Liping, ZHANG Yang, Ding han. 2021. Vertical Air Motion and Raindrop Size Distribution Retrieval Using a Ka/Ku Dual-Wavelength Cloud Radar and Its Preliminary Application [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 45(5): 1−15 doi: 10.3878/j.issn.1006-9895.2104.20200

Ka/Ku双波段云雷达反演空气垂直运动速度和雨滴谱方法研究及初步应用

doi: 10.3878/j.issn.1006-9895.2104.20200
基金项目: 国家自然基金项目41875036,国家重点研发计划项目2018YFC1507400
详细信息
    作者简介:

    刘黎平,男,1963年出生,研究员,主要从事双线偏振雷达、云雷达和相控阵天气雷达探测原理、数据分析方法研究。E-mail: liulp@cma.gov.cn

  • 中图分类号: P412

Vertical Air Motion and Raindrop Size Distribution Retrieval Using a Ka/Ku Dual-Wavelength Cloud Radar and Its Preliminary Application

Funds: National Natural Science Foundation of China (Grant 41875036), National Key R&D Program of China (Grant 2018YFC1507400)
  • 摘要: 在Ka波段云雷达上升级改造建成的Ka/Ku(Ka和Ku波段波长分别为8.9 mm和2.2 cm)双波段云雷达2019年用于华南云降水垂直结构观测,以改进云内动力和微物理参数探测能力。为了利用该双波段云雷达研究华南降水微物理和动力结构,本文提出了基于双波段云雷达回波强度谱密度(SZ)数据和最优估计技术的云内空气垂直运动速度(Vair)、雨滴谱(DSD)、含水量(LWC)、雨强(R)的反演方法(DWSZ),雨区衰减的订正方法。利用2019年在广东龙门观测的一次降水过程数据,对比分析了云雷达反演的微物理参数与雨滴谱直接观测量,并检验了云雷达反演的低层空气垂直运动速度,利用反演结果分析了一次混合云过程的Vair与这些微物理参数的垂直结构和相互关系。结果表明:Ka/Ku双波段云雷达合理反演了微降水微物理和动力参数及其垂直分布,经过衰减订正的Ka和Ku波段回波强度偏差明显减小。该双波段云雷达数据可以用于分析0~30 dBZ回波强度的云降水垂直结构。本次过程为混合云降水,对流单体前部存在明显的上升气流,后部存在下沉气流;从平均垂直结构来看:Vair和粒子平均直径(Dm)在2 km高度层到达最大,粒子数密度(Nw)、LWC和R在2 km以下明显增强,粒子直径却减小,水汽凝结过程、雨滴碰并云滴是本次过程的主要机制。这一工作验证了Ka和Ku波段组合的双波段云雷达的可行性,为Ka/Ku波段云雷达技术的推广,单波段云雷达反演算法进一步改进,云降水精细结构分析等提供了基础。
  • 图  1  2019年5月8日15:30(北京时,下同)双波段云雷达观测的3 km高度上SZKa(黑实线,左侧纵坐标)和SZKu(红实线,左侧纵坐标),两者之比(RR,黑虚线,右侧纵坐标)和理论比值(RS,红虚线,右侧纵坐标)随径向速度的变化

    Figure  1.  SZKa (reflectivity spectral density for Ka-band, black solid line, left y-axis) and SZKu (reflectivity spectral density for Ku-band, red solid line, left y-axis) observed by DWCR, as well as their ratios (RR, black dotted line, right y-axis) and theoretical ratios (RS, red dotted line, right y-axis) at the 3-km height at 1530 BJT (Beijing time) on 8 May 2019

    图  2  2019年5月8日08:00~16:00时段双波段云雷达观测的(a)Ka、(b)Ku波段回波强度(0.3 km高度)与雨滴谱仪观测雨滴谱计算得到的回波强度的散点图

    Figure  2.  Scattering plots of reflectivity for (a) Ka- and (b) Ku-band observed by DWCR (at the height of 0.3 km) and calculated using the disdrometer during 0800–1600 BJT on 8 May 2019

    图  3  2019年5月8日12:00~15:48时段广州市S波段双线偏振雷达观测的回波强度PPI演变图,时间间隔12 min,仰角0.5°。A、B、C、D和相应的圆圈表示双波段云雷达观测到的主要云团

    Figure  3.  PPI (plan position indicator) of reflectivity observed by the Guangzhou S-band polarization weather radar during 1200–1548 BJT on 8 May 2019. The time interval is 12 min, and the elevation angle is 0.5°. A, B, C, D, and corresponding circles represent the convective cells passing through the DWCR

    图  4  2019年5月8日12:23~15:54,M3和M4融合的Ka和Ku波段(a、b)原始回波强度、(c、d)衰减订正后的回波强度、(e)DWSZ方法反演的空气垂直运动速度的时间—高度图

    Figure  4.  Time–height profiles of Ka- and Ku-band (a, b) raw merged reflectivity, (c, d) corrected reflectivity from the M3 and M4 modes, and (e) Vair (vertical velocity for air motion) using DWSZ during 1223–1554 BJT on 8 May 2019

    图  5  2019年5月8日12:23~15:54利用(a)Ka和(b)Ku波段功率谱的SWR方法计算得到的Vair时间—高度图

    Figure  5.  Time–height profiles of Vair retrieved by the tracers of clear-air motion algorithm (SWR) algorithm with (a) Ka- and (b) Ku-band power spectrum during 1223–1554 BJT on 8 May 2019

    图  6  2019年5月8日12:23~15:54时段平均的(a)Ka、Ku原始和订正后的回波强度廓线和(b)利用Ka、Ku波段的SWR以及DWSZ方法反演的三种Vair的垂直廓线

    Figure  6.  Vertical profiles for (a) raw and attenuation-corrected Ka- and Ku-band reflectivity and (b) three types of Vair by SWR and DWSZ averaged during 1223–1554 BJT on 8 May 2019

    图  7  2019年5月8日12:23~15:54时段DWSZ方法反演的(a)Nw、(b)Dm和(c)LWC时间—高度图

    Figure  7.  Time–height profiles of (a) Nw (normalized drop number concentration), (b) Dm (mass-weighted mean diameter), and (c) LWC (liquid water content) retrieved by DWSZ during 1223–1554 BJT on 8 May 2019

    图  8  2019年5月8日12:23~15:54时段平均的(a)ZNw、(b)VairDm、(c)LWC和R的垂直廓线

    Figure  8.  Vertical profiles of (a) Z (reflectivity) and Nw, (b) Vair and Dm, and (c) LWC and R (rain rate) averaged during 1223–1554 BJT on 8 May 2019

    图  9  2019年5月8日08:00~18:00时段雷达反演得到的300 m高度上微物理参数(a)LWC,(b)DmVair,(c)NwVair,(d)Vair(红色线)、Vaird(黑色线),(e)Z与雨滴谱直接观测量(DSD)的比较

    Figure  9.  Time variations of (a) LWC, (b) Dm, Vair, (c) Nw, Vair, (d) Vair (red line), Vaird (black line, vertical velocity for air motion calculated by raindrop spectrum), and (e) Z retrieved with DWSZ at 300-m height and disdrometer-observed (DSD) during 0800–1800 BJT on 8 May 2019

    表  1  Ka/Ku双波段云雷达技术指标

    Table  1.   Ka/Ku DWCR (dual-wavelength cloud radar) technical parameters

    序号 指标项技术规格要求
    系统总体技术指标
    1雷达体制双波段、脉冲多普勒、固态发射机、脉冲压缩
    2工作频率33.44 GHz(Ka波段)、13.6 GHz(Ku波段)
    3探测要素双波段ZVrWsLDRSZ
    4探测威力≤−30 dBZ@5 km(Ka);≤−20 dBZ@5 km(Ku)
    5探测范围高度:120 m~15 km;回波强度:−50~+30 dBZ;径向速度:−20~+20 m s−1(最大);速度谱宽:0~4 m s−1(最大)
    6探测精度时间分辨率:6 s(可调);高度分辨率:30 m;回波强度:≤1 dBZ(RMS);径向速度:≤1 m s−1(RMS);速度谱宽:≤1 m s−1
    天馈分系统
    1工作频率Ka/Ku频段
    2天线类型卡塞格伦天线
    3天线直径2 m(Ka) ,1.8 m(Ku)
    4天线增益≥53 dB(Ka) ,≥45 dB(Ku)
    5波束宽度≤0.35°(Ka) ,≤0.9°(Ku)
    6第一副瓣电平≤−18 dB(Ka)
    7远区副瓣电平≤−40 dB
    8交叉极化隔离度≥30 dB
    9驻波比≤1.5
    10收发馈线损耗≤3 dB
    发射分系统
    1体制全固态发射机
    2峰值功率≥50 W(Ka) ,≥200 W(Ku)
    3占空比≥10%
    接收机和频综分系统
    1噪声系数≤5 dB
    2线性动态范围≥60 dB
    3相位噪声(一本振)≤−96 dBc/Hz@1 kHz
    4中频处理数字中频接收
    信号处理分系统
    1A/D位数≥14位
    2处理方法脉冲压缩、快速傅立叶变换、相干积累和非相干积累等
    3距离库长30 m
    4距离库数≥500
    5输出数据多普勒功率谱分布
    下载: 导出CSV

    表  2  Ka/Ku双波段云雷达四个观测模式参数设置

    Table  2.   Main parameters of DWCR for 4 work modes

    项目M1M2M3M4
    Ka速度分辨率 (m s−1)0.03620.07240.14480.1448
    Ka速度范围 (m s−1)4.6352559.2704518.540918.5409
    Ku速度分辨率 (m s−1)0.089750.17950.35900.3590
    Ku速度范围 (m s−1)11.488622.977245.954445.9544
    脉冲宽度(μs)0.2120.26
    距离分辨力 (m)30303030
    脉冲重复周期 (μs)120120120120
    相干积累(次)4211
    FFT点数(个)256256256256
    非相干积累(个)16326464
    驻留时间 (s)2222
    距离库数(个)500500500500
    盲区(m)30180030900
    下载: 导出CSV
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  • 收稿日期:  2020-09-14
  • 录用日期:  2021-05-06
  • 网络出版日期:  2021-04-10

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