利用Ka波段毫米波雷达功率谱反演云降水大气垂直速度和雨滴谱分布研究
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摘要
利用中国气象科学研究院2016年华南云降水试验中Ka波段毫米波雷达探测一次层状云降水过程,开展了云内大气垂直速度和雨滴谱的反演研究,并与地面激光雨滴谱仪和微降水雷达的测量雨滴谱结果进行对比分析。首先,采用小粒子示踪法从功率谱密度中反演大气垂直速度以得到静止空气条件下的功率谱密度,进而利用粒子下落末速度-粒子直径关系反演出雨滴谱,最后进行标准化的Gamma分布拟合。研究表明:(1)云降水从零度层到地面1 km,主要由下沉气流主导,近地面大气浮游粒子和直流干扰造成的晴空杂波会影响雷达的功率谱分布;受动态范围限制,回波强度过饱和现象会影响近地面大气垂直速度的反演结果;(2)毫米波雷达CR、微雨雷达MRR和地面雨滴谱仪测量回波强度存在一定差异,MRR相较于CR与地面雨滴谱仪测量偏差较小;在稳定降水时CR和MRR功率谱密度对比较为一致;(3) CR和MRR反演雨滴谱对比实验中,雨滴谱反演对大气垂直速度十分敏感,大气垂直速度的变化,会使CR反演雨滴谱随着高度增加数浓度量级变大、粒子平均半径变小。CR反演的雨滴谱与M RR反演结果基本一致,验证了CR功率谱反演雨滴谱方法的可靠性;(4) CR与地面雨滴谱仪雨滴谱拟合参数的对比表明,CR大气垂直反演的雨滴谱与地面雨滴谱相比粒子平均直径Dm较小,数浓度则较为一致。
Vertically pointing Ka-band Millimeter Radar has a good detection sensitivity and high temporal-spatial resolution. The Doppler spectral density data can be utilized to retrieve the detailed cloud structure and microphysical parameters. In this study,a stratiform precipitation case in 2016 CAMs South China Precipitation Test is used to retrieve the vertical air velocity in clouds and drop size distribution,and compare the DSD results with Distrometer and MRR. First,Liquid droplets trace methods is used to get the vertical airspeed which can obtain Doppler spectral in static air. Then we retrieve DSD from the translated Doppler spectrum by a V-D relation.Last,Normalized Gamma Distribution is used to fit the retrieved DSD. Several conclusions are get from the case study:(1) Weak downwards flowdominates the vertical air motions in cloud between the height from 1 km to the 0 ℃ level height. The clear-air echo caused by plankton contamination and noisy echo influence the Doppler spectral,as well as the phenomenon of saturation in Z existing near surface layer and affect the results of vertical air motions too.(2) Differences in Z is found in the detection of CR、MRR and Distrometer. MRR's Z data has a smaller difference with Distrometer than CR. In stable stratiform precipitation,Doppler spectral of CR and MRR are almost consistent.(3) In the comparison test of CR and MRR,DSD retrieval results are highly sensitive to the introduction of vertical Airspeed. Because of airspeed changing with height,DSD from CR has an overall increasing number concentration and decreasing value of average radium. DSDs retrieved by the two instruments' spectrum have a similar distribution along all heights,demonstrating the validity of retrieving DSD from Doppler spectral.(4) In the comparison of Gamma fitting parameters of CR and distrometer,the DSD of CR introducing vertical air motions results in has a smaller Dm and a same Nwmagnitude comparing to Distrometer.
Vertically pointing Ka-band Millimeter Radar has a good detection sensitivity and high temporal-spatial resolution. The Doppler spectral density data can be utilized to retrieve the detailed cloud structure and microphysical parameters. In this study,a stratiform precipitation case in 2016 CAMs South China Precipitation Test is used to retrieve the vertical air velocity in clouds and drop size distribution,and compare the DSD results with Distrometer and MRR. First,Liquid droplets trace methods is used to get the vertical airspeed which can obtain Doppler spectral in static air. Then we retrieve DSD from the translated Doppler spectrum by a V-D relation.Last,Normalized Gamma Distribution is used to fit the retrieved DSD. Several conclusions are get from the case study:(1) Weak downwards flowdominates the vertical air motions in cloud between the height from 1 km to the 0 ℃ level height. The clear-air echo caused by plankton contamination and noisy echo influence the Doppler spectral,as well as the phenomenon of saturation in Z existing near surface layer and affect the results of vertical air motions too.(2) Differences in Z is found in the detection of CR、MRR and Distrometer. MRR's Z data has a smaller difference with Distrometer than CR. In stable stratiform precipitation,Doppler spectral of CR and MRR are almost consistent.(3) In the comparison test of CR and MRR,DSD retrieval results are highly sensitive to the introduction of vertical Airspeed. Because of airspeed changing with height,DSD from CR has an overall increasing number concentration and decreasing value of average radium. DSDs retrieved by the two instruments' spectrum have a similar distribution along all heights,demonstrating the validity of retrieving DSD from Doppler spectral.(4) In the comparison of Gamma fitting parameters of CR and distrometer,the DSD of CR introducing vertical air motions results in has a smaller Dm and a same Nwmagnitude comparing to Distrometer.
引文
Gossard E E,1994.M easurement of cloud droplet size spectra by Doppler Radar[J].Journal of Atmospheric&Oceanic Technology,11(3):712-726.
Hildebrand P H,Sekhon R S,1974.Objective determination of the noise level in Doppler spectra[J].Journal of Applied M eteorology,13(7):808-811.
Kollias P,Albrecht B A,2000.The turbulence structure in a continental stratocumulus cloud from millimeter-w avelength Radar observations[J].Journal of the Atmospheric Sciences,57(57):2417-2434.
Kollias P,Albrecht B A,M arks F,2002.Why M ie?[J].Bulletin of the American M eterological Society,83(10):1471-1483.
Kollias P,Albrecht B A,Lhermitte R,et al,2001.Radar observations of updrafts,dow ndrafts,and turbulence in fair-w eather cumuli[J].Journal of the Atmospheric Sciences,58(13):1750-1766.
Lhermitte R M,1966.Probing air motion by doppler analysis of Radar clear air returns[J].Journal of the Atmospheric Sciences,23(5):575-591.
Petitdidier M,Sy A,Garrouste A,et al,1997.Statistical characteristics of the noise pow er spectral density in UHF and VHF w ind profilers[J].Radio Science,32(3):1229-1247.
Rogers R R,1964.An extension of the Z-R relation for Doppler radars[C].The 11th Weather Radar Conference AMS,Boston,MA.,Goulder,Co.,Sept.,14-18.
Shupe M D,Kollias P,Poellot M,et al,2008.On deriving vertical air motions from cloud Radar Doppler spectra[J].Journal of Atmospheric&Oceanic Technology,25(4):547.
Testud J,Oury S,Black R A,et al,2001.The concept of`normalized’distribution to describe raindrop spectra:A tool for cloud physics and cloud remote sensing[J].Journal of Applied M eteorology,40(40):1118-1140.
Ulbrich C W,1983.Natural Variations in the analytical form of the raindrop size distribution[J].J Climate and Applies M eteorology,22(10):1764-1775.
Yahao W U,Liu L,2017.Statistical characteristics of raindrop size distribution in the Tibetan Plateau and Southern China[J].Advances in Atmospheric Sciences,34(6):727-736.
Zheng J F,Liu L P,Zhu K Y,et al,2017.A method for retrieving vertical air velocities in convective clouds over the Tibetan Plateau from TIPEX-ⅢCloud Radar DopplerSpectra[J].Remote Sensing,9(9):964.
樊雅文,2012.云雷达资料订正及应用研究[D].南京:南京信息工程大学.
刘黎平,谢蕾,崔哲虎,2014.毫米波云雷达功率谱密度数据的检验和在弱降水滴谱反演中的应用研究[J].大气科学,38(2):223-236.
刘黎平,周淼,2016.垂直指向的Ka波段云雷达观测的0℃层亮带自动识别及亮带的特征分析[J].高原气象,35(3):734-744.DOI:10.7522/j.issn.1000-0534.2014.00160.
彭亮,陈洪滨,李柏,2012.3 mm多普勒云雷达测量反演云内空气垂直速度的研究[J].大气科学,36(1):1-10.
阮悦,阮征,魏鸣,等,2018.基于C-FMCW雷达的高原夏季对流云垂直结构分析研究[J].高原气象,37(1):93-105.DOI:10.7522/j.issn.1000-0534.2017.00025.
孙豪,刘黎平,2017.不同波段垂直探测雷达对降水云雨滴谱反演效果对比分析[J].成都信息工程大学学报,32(1):35-40.
王洪,雷恒池,杨洁帆,2017.微降水雷达测量精度分析[J].气候与环境研究,22(4):392-404.
温龙,刘溯,赵坤,等,2015.两次降水过程的微降雨雷达探测精度分析[J].气象,41(5):577-587.
谢蕾,刘黎平,姚雯,2014.毫米波雷达与雨滴谱仪观测弱降水的对比分析[J].成都信息工程学院学报,29(1):39-46.
吴亚昊,刘黎平,周筠珺,等,2016.雨滴谱的变化对降水估测的影响研究[J].高原气象,35(1):220-230.DOI:10.7522/j.issn.1000-0534.2014.00093.
姚志刚,杨超,赵增亮,等,2018.毫米波雷达反演层状云液态水路径研究[J].高原气象,37(1):223-233.DOI:10.7522/j.issn.1000-0534.2016.00127.
郑佳锋,刘黎平,刘艳霞,等,2016a.云雷达回波强度谱密度定标及云内大气垂直运动速度反演试验[J].高原气象,35(6):1650-1661.DOI:10.7522/j.issn.1000-0534.2015.00064.
郑佳锋,刘黎平,曾正茂,等,2016b.Ka波段毫米波云雷达数据质量控制方法[J].红外与毫米波学报,35(6):748-757.
郑娇恒,陈宝君,2007.雨滴谱分布函数的选择:M-P和Gamma分布的对比研究[J].气象科学,27(1):17-25.
Hildebrand P H,Sekhon R S,1974.Objective determination of the noise level in Doppler spectra[J].Journal of Applied M eteorology,13(7):808-811.
Kollias P,Albrecht B A,2000.The turbulence structure in a continental stratocumulus cloud from millimeter-w avelength Radar observations[J].Journal of the Atmospheric Sciences,57(57):2417-2434.
Kollias P,Albrecht B A,M arks F,2002.Why M ie?[J].Bulletin of the American M eterological Society,83(10):1471-1483.
Kollias P,Albrecht B A,Lhermitte R,et al,2001.Radar observations of updrafts,dow ndrafts,and turbulence in fair-w eather cumuli[J].Journal of the Atmospheric Sciences,58(13):1750-1766.
Lhermitte R M,1966.Probing air motion by doppler analysis of Radar clear air returns[J].Journal of the Atmospheric Sciences,23(5):575-591.
Petitdidier M,Sy A,Garrouste A,et al,1997.Statistical characteristics of the noise pow er spectral density in UHF and VHF w ind profilers[J].Radio Science,32(3):1229-1247.
Rogers R R,1964.An extension of the Z-R relation for Doppler radars[C].The 11th Weather Radar Conference AMS,Boston,MA.,Goulder,Co.,Sept.,14-18.
Shupe M D,Kollias P,Poellot M,et al,2008.On deriving vertical air motions from cloud Radar Doppler spectra[J].Journal of Atmospheric&Oceanic Technology,25(4):547.
Testud J,Oury S,Black R A,et al,2001.The concept of`normalized’distribution to describe raindrop spectra:A tool for cloud physics and cloud remote sensing[J].Journal of Applied M eteorology,40(40):1118-1140.
Ulbrich C W,1983.Natural Variations in the analytical form of the raindrop size distribution[J].J Climate and Applies M eteorology,22(10):1764-1775.
Yahao W U,Liu L,2017.Statistical characteristics of raindrop size distribution in the Tibetan Plateau and Southern China[J].Advances in Atmospheric Sciences,34(6):727-736.
Zheng J F,Liu L P,Zhu K Y,et al,2017.A method for retrieving vertical air velocities in convective clouds over the Tibetan Plateau from TIPEX-ⅢCloud Radar DopplerSpectra[J].Remote Sensing,9(9):964.
樊雅文,2012.云雷达资料订正及应用研究[D].南京:南京信息工程大学.
刘黎平,谢蕾,崔哲虎,2014.毫米波云雷达功率谱密度数据的检验和在弱降水滴谱反演中的应用研究[J].大气科学,38(2):223-236.
刘黎平,周淼,2016.垂直指向的Ka波段云雷达观测的0℃层亮带自动识别及亮带的特征分析[J].高原气象,35(3):734-744.DOI:10.7522/j.issn.1000-0534.2014.00160.
彭亮,陈洪滨,李柏,2012.3 mm多普勒云雷达测量反演云内空气垂直速度的研究[J].大气科学,36(1):1-10.
阮悦,阮征,魏鸣,等,2018.基于C-FMCW雷达的高原夏季对流云垂直结构分析研究[J].高原气象,37(1):93-105.DOI:10.7522/j.issn.1000-0534.2017.00025.
孙豪,刘黎平,2017.不同波段垂直探测雷达对降水云雨滴谱反演效果对比分析[J].成都信息工程大学学报,32(1):35-40.
王洪,雷恒池,杨洁帆,2017.微降水雷达测量精度分析[J].气候与环境研究,22(4):392-404.
温龙,刘溯,赵坤,等,2015.两次降水过程的微降雨雷达探测精度分析[J].气象,41(5):577-587.
谢蕾,刘黎平,姚雯,2014.毫米波雷达与雨滴谱仪观测弱降水的对比分析[J].成都信息工程学院学报,29(1):39-46.
吴亚昊,刘黎平,周筠珺,等,2016.雨滴谱的变化对降水估测的影响研究[J].高原气象,35(1):220-230.DOI:10.7522/j.issn.1000-0534.2014.00093.
姚志刚,杨超,赵增亮,等,2018.毫米波雷达反演层状云液态水路径研究[J].高原气象,37(1):223-233.DOI:10.7522/j.issn.1000-0534.2016.00127.
郑佳锋,刘黎平,刘艳霞,等,2016a.云雷达回波强度谱密度定标及云内大气垂直运动速度反演试验[J].高原气象,35(6):1650-1661.DOI:10.7522/j.issn.1000-0534.2015.00064.
郑佳锋,刘黎平,曾正茂,等,2016b.Ka波段毫米波云雷达数据质量控制方法[J].红外与毫米波学报,35(6):748-757.
郑娇恒,陈宝君,2007.雨滴谱分布函数的选择:M-P和Gamma分布的对比研究[J].气象科学,27(1):17-25.