利用2013 年垂直指向的Ka波段云雷达在广东观测的弱降水个例,分析了回波强度Z、径向速度Vr 和退偏振因子LDR在0 ℃层附近的变化规律,利用建模样本提出了基于云雷达垂直观测Z、Vr 和LDR数据的0 ℃层亮带自动识别方法,并利用独立观测样本进行了识别算法的检验,分析了Vr 数据对识别效果的影响,与每天四次探空得到的数据进行了对比。结果表明,在0 ℃层亮带内,Z 和LDR的极大值的高度和Z、Vr、LDR这三个物理量在垂直方向上的突变范围都一致,0 ℃层亮带的厚度与Z、Vr 和LDR的变化量有一定的关系,在0 ℃层亮带特征较明显的回波上部也存在明显的空气上升运动。Vr 和LDR是识别0 ℃层亮带的关键因子,而Z可能因云的位置和复杂的云层而产生剧烈的垂直变化。该算法可以较好识别典型的0 ℃层亮带,正确提取主要参数,而云的边缘和多层云等情况会影响0 ℃层亮带的识别。为利用Ka波段云雷达数据分析弱降水的性质提供了算法。
Reflectivity(Z),radial velocity(Vr)and depolarization ratio(LDR)in weak precipitation in Guangdong were observed by vertical pointed Ka band cloud radar in 2013.The statistical characteristics of bright band (BB)are analyzed and the automatic algorithm to detect BB is developed based on the vertical profiles of Z,Vr and LDR.The sounding data are used to examine the detection algorithm.The results show that the sharp variations patterns of Z and LDR with height and positions with maximum Z and LDR are similar.The ranges with sharp variations of Z,Vr and LDR are corresponding well.The thickness of BB is obvious correlation with Z,variations of Vr and LDR within BB.The updrafts often exist in the top of cloud for bright band case.Vr and LDR are key factors for detection of BB,however sharp variations of Z often occur in the edge of cloud system.The detection algorithm could detect the typical BB and non-BB,the cloud edge and multi-layer cloud could affect the detection algorithm.This work provides the productions for cloud physical research.
[1]Austin P M,Bemis A.1950.A quantitative study of the bright band in radar precipitation echoes[J].J Meteor,7:165-171.
[2]Brandes E A,Ikeda K.2004.Freezing-level estimation with polarimetric radar[J].J Appl Meteor,43(11):1541-1553.
[3]Fabry F,Zawadzki I.1995.Long-term radar observations of the melting layer of precipitation and their interpretation[J].J Atmos Sci,52:838-851.
[4]Gourley J,Calvert C.2003.Automated detection of the bright band using WSR-88D data [J].Wea Forecasting,18:585-599.
[5]Kain J S,Goss S M,Baldwin M E.2000.The melting effect as a factor in precipitation-type forecasting[J].Wea Forecasting,15:700-714.
[6]Kitchen M,Jackson P M.1993.Weather radar performance at long range-Simulated and observed[J].J Appl Meteor,32:975-985.
[7]Shupe M D.2007.A ground-based multisensor cloud phase classifier[J].Geophys Res Lett,34,L22809.DOI:10.1029/2007GL031008.
[8]Smith C J.1986.The reduction of errors caused by bright bands in quantitative rainfall measurements made using radar[J].J Atmos Oceanic Technol,3:129-141.
[9]White A B,Gottas D J,Strem E T,et al.2002.An automated bright band height detection algorithm for use with Doppler radar spectral moments[J].J Atmos Oceanic Technol,19:687-697.
[10]曹俊武,刘黎平.2007.双线偏振雷达判别降水粒子类型技术及其检验[J].高原气象,26(1):116-127.Cao Junwu,Liu Liping.2007.The sensitivity study for classification of precipitation particle types based on dual-linear polarimetric radar[J].Plateau Meteor,26(1):116-127.
[11]陈明轩,高峰.2006.利用一种自动识别算法移除天气雷达反射率因子中的亮带[J].应用气象学报,17(2):207-215.Chen Mingxuan,Gao Feng.2006.An automatic identification algorithm for the removal of bright band from reflectivity of CINRAD/SA [J].J Appl Meteor Sci,17(2):207-215.
[12]杜牧云,刘黎平,胡志群,等.2013.双线偏振雷达差分反射率因子系统误差订正[J].高原气象,32(4):1174-1185.Du Muyun,Liu Liping,Hu Zhiqun,et al.2013.System bias calibration of differential reflectivity for dual linear polarization radar [J].Plateau Meteor,32(4):1174-1185.DOI:10.7522/j.issn 1000-0534.2012.00084.
[13]勾亚彬,刘黎平,李瑞义,等.2015.基于雷达回波概率特征的雷达部分遮挡区域识别算法[J].高原气象,34(2):556-567.Gou Yabin,Liu Liping,Li Ruiyi,et al.2015.Radar partial shielding region identification algorithm based on the probability characteristics of radar echoes[J].Plateau Meteor,34(2):556567.DOI:10.7522/j.issn.1000-0534.2013.00192.
[14]黄毅梅,周毓荃.2012.95GHz云雷达对一次冷锋云系结构的观测分析[J].高原气象,31(4):11291138.Huang Yimei,Zhou Yuquan.2012.Analysis on cold front cloud structure from 95 GHz cloud radar data[J].Plateau Meteor,31(4):1129-1138.
[15]黄钰,阮征,葛润生,等.2011.风廓线雷达探测零度层亮带的试验研究[J].高原气象,30(5):1376-1383.Huang Yu,Ruan Zheng,Ge Runsheng,et al.2011.Study on bright band detection using wind profiler radar[J].Plateau Meteor,30(5):1376-1383.
[16]彭亮,陈洪滨,李柏.2011.模糊逻辑法在3 mm云雷达反演云中水凝物粒子相态中的应用 [J].遥感技术与应用,26(5):655-663.Peng Liang,Chen Hongbin,Li Bai.2011.An application of Fuzzy logic method to cloud hydrometeor classifications using the ARM WACR data [J].Remote Sensing Technology and Application,26(5):655-663.
[17]孙晓光,刘宪勋,贺宏兵,等.2011.毫米波测云雷达融化层自动识别技术[J].气象,37 (6):720726.Sun Xiaoguang,Liu Xianxun,He Hongbing,et al.2011.Automatic identification technology of melting layer in millimeter wave cloud radar data[J].Meteor Mon,37(6):720-726.
[18]王德旺,刘黎平,仲凌志,等.2012.毫米波雷达资料融化层亮带特征的分析及识别[J].气象,38 (6):712-721.Wang Dewang,Liu Liping,Zhong Lingzhi et al.2012.Analysis of the characters of melting layer of cloud radar data and its identification[J].Meteor Mon,38(6):712-721.
[19]肖艳姣,刘黎平,李中华,等.2010.雷达反射率因子数据中的亮带自动识别和抑制[J].高原气象,29(1):197-205.Xiao Yanjiao,Liu Liping,Li Zhonghua,et al.2010.Automatic recognition and removal of the bright band using radar reflectivity data [J].Plateau Meteor,29(1):197-205.
[20]张乐坚,程明虎,陶岚.2010.CINRAD-SA/SB零度层亮带识别方法[J].应用气象学报,21(2):171-179.Zhang Lejian,Cheng Minghu,Tao Lan.2010.Bright band identification from CINRAD-SA/SB [J].J Appl Meteor Sci,21(2):171-179.
[21]庄薇,刘黎平,胡志群.2013.青藏高原零度层亮带的识别订正方法及在雷达估测降水中的应用[J].气象,39(8):1004-1013.Zhuang Wei,Liu Liping,Hu Zhiqun.2013.Application of bright band identification and correction in radar-based QPE over Tibetan Plateau [J].Meteor Mon,39(8):1004-1013.
