Evaluating the Algorithm for Correction of the Bright Band Effects in QPEs with S-, C- and X-Band Dual-Polarized Radars
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The bright band, a layer of enhanced radar reflectivity associated with melting ice particles, is a major source of significant overestimation in quantitative precipitation estimation (QPE) based on the Z–R (reflectivity factor–rain rate) relationship. The effects of the bright band on radar-based QPE can be eliminated by vertical profile of reflectivity (VPR) correction. In this study, we applied bright-band correction algorithms to evaluate three different bands (S-, C- and X-band) of dual-polarized radars and to reduce overestimation errors in Z–R relationship–based QPEs. After the reflectivity was corrected by the algorithms using average VPR (AVPR) alone and a combination of average VPR and the vertical profile of the copolar correlation coefficient (AVPR+CC), the QPEs were derived. The bright-band correction and resulting QPEs were evaluated in eight precipitation events by comparing to the uncorrected reflectivity and rain-gauge observations, separately. The overestimation of Z–R relationship–based QPEs associated with the bright band was reduced after correction by the two schemes for which hourly rainfall was less than 5 mm. For the verification metrics of RMSE (root-mean-square error), RMAE (relative mean absolute error) and RMB (relative mean bias) of QPEs, averaged over all eight cases, the AVPR method improved from 2.28, 0.94 and 0.78 to 1.55, 0.60 and 0.40, respectively, while the AVPR+CC method improved to 1.44, 0.55 and 0.30, respectively. The QPEs after AVPR+CC correction had less overestimation than those after AVPR correction, and similar conclusions were drawn for all three different bands of dual-polarized radars.
Key wordsdual-polarized radar bright band QPE vertical profile of reflectivity
零度层亮带是指融化的冰晶粒子造成反射率因子增大的带区, 其存在会引起基于Z-R关系的定量估测降水(QPE)明显高估. 采用反射率因子垂直廓线(VPR)进行零度层亮带订正可以减弱QPE高估. 本文将此订正方法应用于三个不同波段(S, C, X)的双线偏振雷达上, 以减小QPE高估误差. 采用平均反射率因子垂直廓线法(AVPR)和平均反射率因子垂直廓线与平均相关系数垂直廓线相结合的方法(AVPR+CC)分别对反射率因子进行订正, 采用8次降水过程比较订正前后反射率因子反演的降水, 并与地面雨量站实测降水比较. 结果表明, 当小时降雨量小于5mm时, 两种订正方法均能有效减弱零度层亮带存在引起的QPE高估. 采用均方根误差, 相对平均绝对误差和相对平均偏差三个参数进行误差分析, 平均来看, AVPR法分别从2.28, 0.94和0.78提高到1.55, 0.60和0.40, AVPR+CC法分别提高到1.44, 0.55和0.30. AVPR+CC法订正后的反射率因子反演的QPE误差小于AVPR法, 三个波段雷达具有相似的结果.
关键词双偏振雷达 零度层亮带 定量估测降水 反射率因子垂直廓线
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This research was funded by a China National 973 Program on Key Basic Research project (Grant No. 2014CB441401), the Beijing Municipal Natural Science Foundation (Grant No. 8141002), and the Public Welfare Industry (Meteorology) of China (Grant No. GYHY201106046). The authors greatly appreciate the immense assistance provided by the other participants at the Institute of Atmospheric Physics and the Meteorological Bureau of Beijing and Xiamen, China.
- Hubbert, J. C., S. M. Ellis, M. Dixon, and G. Meymaris, 2010: Modeling, error analysis, and evaluation of dual-polarization variables obtained from simultaneous horizontal and vertical polarization transmit radar. Part I: Modeling and antenna errors. J. Atmos. Oceanic Technol., 27, 1583–1598, https://doi.org/10.1175/2010JTECHA1336.1.Google Scholar
- Kalogiros, J., M. N. Anagnostou, E. N. Anagnostou, M. Montopoli, E. Picciotti, and F. S. Marzano, 2013: Correction of polarimetric radar reflectivity measurements and rainfall estimates for apparent vertical profile in stratiform rain. Journal of Applied Meteorology and Climatology, 52, 1170–1186, https://doi.org/10.1175/JAMC-D-12-0140.1.CrossRefGoogle Scholar
- Liu, X. Y., H. P. Yang, J. T. Li, B. Li, K. Zhao, and Y. Y. Zheng, 2010: CINRAD radar quantitative precipitation estimation group system. Meteorological Monthly, 36, 90–95. (in Chinese with English abstract).Google Scholar
- Park, S. G., V. N. Bringi, V. Chandrasekar, M. Maki, and K. Iwanami, 2005a: Correction of radar reflectivity and differential reflectivity for rain attenuation at X band. Part I: Theoretical and empirical basis. J. Atmos. Oceanic Technol., 22, 1621–1632, https://doi.org/10.1175/JTECH1803.1.CrossRefGoogle Scholar
- Park, S. G., M. Maki, K. Iwanami, V. N. Bringi, and V. Chandrasekar, 2005b: Correction of radar reflectivity and differential reflectivity for rain attenuation at X band. Part II: Evaluation and application. J. Atmos. Oceanic Technol., 22, 1633–1655, https://doi.org/10.1175/JTECH1804.1.CrossRefGoogle Scholar
- Shusse, Y., N. Takahashi, K. Nakagawa, S. Satoh, and T. Iguchi, 2011: Polarimetric radar observation of the melting layer in a convective rainfall system during the rainy season over the East China Sea. Journal of Applied Meteorology and Climatology, 50, 354–367, https://doi.org/10.1175/2010JAMC2469.1.CrossRefGoogle Scholar
- Sun, H. M., P. Y. Zhang, Z. Jiang, and H. Y. Li, 2015: Automated correction of the bright band of weather radar reflectivity data in radar quantitative precipitation estimation. Transactions of Atmospheric Sciences, 38, 492–501, https://doi.org/10.13878/j.cnki.dqkxxb.20121207001 (in Chinese with English abstract)Google Scholar
- White, A. B., P. J. Neiman, F. M. Ralph, D. E. Kingsmill, and P. O. G. Persson, 2003: Coastal orographic rainfall processes observed by radar during the California Land-Falling Jets Experiment. Journal of Hydrometeorology, 4, 264–282, https://doi.org/10.1175/1525-7541(2003)4<264:CORPOB>2.0.CO;2.CrossRefGoogle Scholar
- Wu, C., L. P. Liu, M. Wei, B. Z. Xi, and M. H. Yu, 2018: Statistics-based optimization of the polarimetric radar Hydrometeor Classification Algorithm and its application for a squall line in South China. Adv. Atmos. Sci., 35(3), 296–316, https://doi.org/10.1007/s00376-017-6241-0.CrossRefGoogle Scholar
- Xiao, Y. J., L. P. Liu, Z. H. Li, and H. Y. Wang, 2010: Automatic recognition and removal of the bright band using radar reflectivity data. Plateau Meteorology, 29, 197–205. (in Chinese with English abstract).Google Scholar
- Zhang, J., Y. C. Qi, D. Kingsmill, and K. Howard, 2012: Radarbased quantitative precipitation estimation for the cool season in complex terrain: Case studies from the NOAA hydrometeorology testbed. Journal of Hydrometeorology, 13, 1836–1854, https://doi.org/10.1175/JHM-D-11-0145.1.CrossRefGoogle Scholar
- Zhuang, W., L. P. Liu, and Z. Q. Hu, 2013: Application of bright band identification and correction in radar-based QPE over Tibetan Plateau. Meteorological Monthly, 39, 1004–1013, https://doi.org/10.7519/j.issn.1000-0526.2013.08.007. (in Chinese with English abstract)Google Scholar