The dual pulse repetition frequency (dual PRF) technique is available to extend the unambiguous velocity interval of Doppler weather radar, but the velocity data are typically contaminated by discrete outliers in large areas of high quality data. The quality control is needed before using the radial velocity data. The radial velocity data from CINRAD-SA, SC, CC and CD type Doppler weather radar running in dual PRF mode have been analyzed quantitatively through calculating the deviations of each radial velocity from its local median velocity. On this basis, a three-step postprocessing algorithm is proposed. First of all, the dual PRF velocity data are filtered based on the size to remove the isolated noise. Secondly, aliased velocity data that fall outside of the extended unambiguous velocity interval are unfolded using local continuity constraints. And lastly, using the known error characteristics of the dual PRF velocity data, velocity outliers are corrected in an efficient way. The algorithm has been tested using dual PRF velocity data from CINRAD-SA, SC, CD and CC type Doppler weather radars. The results of dual PRF velocity data analysis show the vast majority of the analyzed points obeys local continuity with hardly any deviation or small deviation from the local median velocity, the fraction of outliers are centered at different velocity deviations which roughly match the unambiguous intervals of the low PRF and high PRF measurements. The results of the algorithm testing show that it can correct effectively aliased velocities and discrete outliers caused by dual PRF mode. After quality control using this algorithm, high quality velocity data with changeless spatial resolution are produced.
[1]Banjanin Z B, Zrnic D S.1991.Clutter rejection for Doppler weather radars which use staggered pulses[J].IEEE Trans Geosci Remote Sens, 29(4):610-620.
[2]Dazhang T, Geotis S G, Passarelli R E.1984.Evaluation of an alternating-PRF method for extending the range of unambiguous Doppler velocity[C]//Preprints, 22<sup>th</sup> Conference on Radar Meteorology, Zurich, Switzerland, Amer Meteor Soc, 523-527.
[3]Holleman I, Beekhuis J.2003.Analysis and correction of dual-PRF velocity data[J].J Atmos Ocean Technol, 20(4):443-453.
[4]Hondl K D, Eilts M D.1993.Evaluation of Doppler velocity dealiasing techniques for low-Nyquist velocity data[C]//Preprints, 26<sup>th</sup> Conference on Radar Meteorology, Norman, OK, Amer Meteor Soc, 59-61.
[5]Joe P, May P T.2003.Correction of dual PRF velocity errors for operational Doppler weather radars[J].J Atmos Ocean Technol, 20(4):429-442.
[6]May P T.2001.Mesocyclone and microburst signature distortion with dual PRT radars[J].J Atmos Ocean Technol, 18(7):1229-1233.
[7]Sirmans D, Zrnic D, Bumgarner B.1976.Extension of maximum unambiguous Doppler velocity by use of two sampling rates[C]//Preprints, 17<sup>th</sup> Conference on Radar Meteorology, Seattle, WA, Amer Meteor Soc, 23-28.
[8]楚志刚, 银燕, 顾松山.2013.一种抗噪声的天气雷达速度退模糊新算法[J].气象学报, 71(4):743-753.Chu Zhigang, Yin Yan, Gu Songshan.2013.A new anti-noise dealiasing algorithm for weather radar velocities[J].Acta Meteor Sinica, 71(4):743-753.
[9]梁海河, 张沛源, 葛润生.2002.多普勒天气雷达风场退模糊方法的研究[J].应用气象学报, 13(5):591-600.Liang Haihe, Zhang Peiyuan, Ge Runsheng.2002.Study of data processing of wind fields from Doppler radar[J].J Appl Meteor Sci, 13(5):591-600.
[10]刘黎平, 吴林林, 杨引明.2007.基于模糊逻辑的分步式超折射地物回波识别方法的建立和效果分析[J].气象学报, 65(2):252-260.Liu Liping, Wu Linlin, Yang Yinming.2007.Development of fuzzy-logical two-step ground clutter detection algorithm[J].Acta Meteor Sinica, 65(2):252-260.
[11]潘新民, 熊毅, 柴秀梅, 等.2010.新一代天气雷达数据退模糊方法探讨[J].气象与环境科学, 33(1):17-23.Pan Xinmin, Xiong Yi, Chai Xiumei, et al.2010.Discussion on the CINRAD correcting data ambiguity method[J].Meteor Environ Sci, 33(1):17-23.
[12]肖艳姣, 万玉发, 王珏, 等.2012.一种自动多普勒雷达速度退模糊算法研究[J].高原气象, 31(4):1119-1128.Xiao Yanjiao, Wan Yufa, Wang Jue, et al.2012.Study of an automated Doppler radar velocity dealiasing algorithm[J].Plateau Meteor, 31(4):1119-1128.
[13]肖艳姣, 万玉发, 吴涛, 等.2015.基于多普勒天气雷达的两种垂直风廓线反演方法的对比分析[J].高原气象, 34(1):288-297.Xiao Yanjiao, Wan Yufa, Wu Tao, et al.2015.Intercomparison of vertical wind profiles retrieved using two techniques from Doppler weather radar[J].Plateau Meteor, 34(1):288-297.DOI:10.7522/j.issn.1000-0534.2013.00136.
[14]徐芬, 王博妮, 夏文梅, 等.2014.长江中下游地区一次春季暴雨过程的多普勒雷达速度特征分析与研究[J].高原气象, 33(2):548-556.Xu Fen, Wang Boni, Xia Wenmei, et al.2014.Analysis on characteristics of Doppler radar velocity in a heavy rain process in spring in mid-and lower-reaches of Yangtze river basin[J].Plateau Meteor, 33(2):548-556.DOI:10.7522/j.issn.1000-0534.2012.00195.
[15]杨川, 刘黎平, 胡志群, 等.2012.C波段多普勒雷达双PRF模式速度混淆区识别和处理方法研究[J].气象学报, 70(4):875-886.Yang Chuan, Liu Liping, Hu Zhiqun, et al.2012.An algorithm for chaos radial velocity identifying and processing in C band Doppler radars running in the dual PRF mode[J].Acta Meteor Sinica, 70(4):875-886.
[16]俞小鼎, 姚秀萍, 熊廷南, 等.2007.多普勒天气雷达原理与业务应用[M].北京:气象出版社, 32-37.Yu Xiaoding, Yao Xiuping, Xiong Tingnan, et al.2007.Doppler weather radar principle and operational applications[M].Beijing:China Meteorological Press, 32-37.
[17]张培昌, 杜秉玉, 戴铁丕.2001.雷达气象学[M].北京:气象出版社, 249-252.Zhang Peichang, Du Bingyu, Dai Tiepi.2001.Radar meteorology[M].Beijing:China Meteorological Press, 249-252.
[18]张一平, 俞小鼎, 孙景兰, 等.2014.一次槽后型大暴雨伴冰雹的形成机制和雷达观测分析[J].高原气象, 33(6):1093-1104.Zhang Yiping, Yu Xiaoding, Zhang Jinglan, et al.2014.Formation mechanism and analysis of radar observation of a heavy rainstorm accompanied by hail that back of trough[J].Plateau Meteor, 33(6):1093-1104.DOI:10.7522/j.issn.1000-0534.2012.00200.
[19]周海光.2009.2008年8月1-2日滁州特大暴雨双多普勒雷达三维风场反演试验的初步结果[J].高原气象, 28(6):1422-1433.Zhou Haiguang.2009.Preliminary study on 3D structure with dual-Doppler radar of heavy rainstorm in Chuzhou area during 1-2 August 2008[J].Plateau Meteor, 28(6):1422-1433.
[20]王遂缠, 胡向军, 张新荣, 等.2011.雷达资料同化在甘肃局地暴雨天气个例中的应用[J].高原气象, 30(3):711-718.Wang Suican, Hu Xiangjun, Zhang Xinrong, et al.2011.Application of doppler radar data assimilation in a local rainstorm case in Gansu Province[J].Plateau Meteor, 30(3):711-718.
