| 微降水雷达测量精度分析 |
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| 引用本文： | 王洪,雷恒池,杨洁帆.微降水雷达测量精度分析[J].气候与环境研究,2017,22(4):392-404. |
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| 作者姓名： | 王洪 雷恒池 杨洁帆 |
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| 作者单位： | 中国科学院大气物理研究所云降水物理与强风暴实验室, 北京 100029;中国科学院大学, 北京 100049;山东省气象信息中心, 济南 250031,中国科学院大气物理研究所云降水物理与强风暴实验室, 北京 100029;中国科学院大学, 北京 100049,中国科学院大气物理研究所云降水物理与强风暴实验室, 北京 100029 |
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| 基金项目： | 国家自然科学基金41475028、41530427，山东省气象局项目2014SDQXZ03、2013SDQXZ04 |
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| 摘 要： | 利用数值模拟的方法,讨论了利用微降水雷达MRR(Micro Rain Radar)雷达功率谱密度反演降水参数时,MIE散射(米散射)效应、垂直气流(包括上升气流、下沉气流)对数浓度N、雷达反射率Z、雨强I、液态含水量LWC等参数的影响。MIE散射主要影响直径为1.20~4.00 mm的粒子,MIE散射效应影响的N、Z、I、LWC偏差的平均值分别为2.74 m-3 mm-1、1.47 d BZ、0.0061 mm h~(-1)、0.0004 g m-3。下沉气流使反演液滴直径偏大,上升气流使得反演的液滴直径偏小,下沉气流的影响更大,尤其是对低层影响大于高层。例如,在300 m高度上,当液滴直径为2.67 mm时,下沉气流为2.00 m s-1时,理论上反演的直径为8.07 mm,超出了MRR探测的阈值,其相对误差值能接近200%。下沉气流使得反射率谱向大粒子方向平移,且谱型展宽;上升气流则相反。将MRR资料与同步观测的THIES雨滴谱仪数据进行比对,分析MRR资料的可靠性。选取2015年4月1日01~12时(协调世界时)山东济南的一次降水过程,将MRR在300 m高度上反演的雷达反射率因子、雨强、数浓度、中值体积直径与雨滴谱仪资料进行对比。结果表明:两种仪器探测的Z、I、N、中值体积直径D0在时间序列上都有较好的吻合度,变化趋势和幅度相近,Z、I、D0的平均偏差分别为1.19 d BZ、0.34 mm h~(-1)、0.36 mm。MRR反演的I值偏大,而粒子直径偏小,分析了产生偏差的主要原因,除了探测系统偏差、分析方法本身存在的偏差外,上升气流导致的偏差不容忽视。这些结果初步验证了微降水雷达观测的功率谱密度及其反演方法的可靠性。
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| 关 键 词： | 微降水雷达 MIE散射 垂直气流 精度验证 |
| 收稿时间： | 2016/8/29 0:00:00 |
Analysis of Measurement Accuracy of Micro Rain Radar |
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| WANG Hong,LEI Hengchi and YANG Jiefan.Analysis of Measurement Accuracy of Micro Rain Radar[J].Climatic and Environmental Research,2017,22(4):392-404. |
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| Authors: | WANG Hong LEI Hengchi and YANG Jiefan |
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| Institution: | Key Laboratory of Cloud-Precipitation Physics and Severe Storms, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;University of Chinese Academy of Sciences, Beijing 100049;Shandong Provincial Meteorological Information Center, Jinan 250031,Key Laboratory of Cloud-Precipitation Physics and Severe Storms, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;University of Chinese Academy of Sciences, Beijing 100049 and Key Laboratory of Cloud-Precipitation Physics and Severe Storms, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | The effects of MIE scattering and vertical motion, including updrafts and downdrafts, on number concentration (N), radar reflectivity (Z), Rain Rate (I), Liquid Water Content (LWC) retrieved from the Doppler spectral density observed by Micro Rain Radar (MRR) are discussed in this study using numerical simulation method. MIE scattering mainly affects 1.20-4.00 mm diameter droplets. The mean deviation caused by MIE scattering is 2.74 m-3 mm-1 for N, 1.47 dBZ for Z, 0.0061 mm h-1 for I and 0.0004 g m-3 for LWC. The retrieved diameter is increased by downdrafts and decreased by updrafts, while downdrafts have greater influences on the retrieved diameter than updrafts, and the influence in lower altitude is greater than that in higher altitude. For instance, when the droplet diameter is 2.67 mm and the velocity of downdraft is 2.00 m s-1 at 300 m height, the relative bias of the theoretical inversion (8.07 mm) is close to 200%, which is close to MRR threshold for droplet diameter. Meanwhile, downdrafts make the Doppler spectral density broaden and move towards particles with larger diameter, whereas effects of updrafts are opposite. To analyze the reliability of MRR, MRR data are compared with the data from the synchronous observations of disdrometer THIES. A precipitation event observed by MRR and disdrometer occurred during 0100 UTC to 1200 UTC 1 April 2015 at Jinan, Shandong Province. Observations of this event are used to examine the MRR data quality. Radar reflectivity, rain rate, number concentration, and median volume diameter (D0) observed by MRR at the third gate are compared with observations of disdrometer. The result indicates that Z, I, N, D0 detected by MRR and disdrometer agree well with similar variations and changing tendencies. Deviations of Z, I, and D0 are 1.19 dBZ, 0.34 mm h-1, 0.36 mm, respectively. Nevertheless, the values of I retrieved by MRR are larger and the diameter is smaller than that of distrometer. These biases are caused by updrafts in addition to systematic biases of the two instruments and analytical methods. Therefore, this study has verified the reliability of Doppler spectral density observed by MRR and retrieval parameters. |
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| Keywords: | Micro Rain Radar MIE scattering Vertical motion Precision verification |
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