Accuracy of dual-polarimetric parameters from a commercially built operational S-band dual-polarization radar

The differential reflectivity can improve the accuracy of rainfall estimate and to identify the existence of hails. This advantage can be undermined by mis-calibration and statistical sampling uncertainty. The accurate calibration of reflectivity further improves the accuracy in rain estimation. In this study, the system bias of reflectivity and differential reflectivity and statistical uncertainty of all measurable are quantified. The self-consistency constraint between radar reflectivity and specific differential phase shift is used to determine the reflectivity calibration bias. In addition, the calibration of differential reflectivity is done by measuring differential reflectivity in vertically pointing mode. The calibration of radar reflectivity was done by comparison of measured phase shift (ФDP) along a ray with calculated ФDP from reflectivity using the climatological relationships ZH = 3.67x104 KDP1.10. This comparison is performed for all rays longer than 10km. If non-rain targets are observed with in a ray, this ray was excluded. The calibration bias of reflectivity is -2.7dB and this value maintains after 16 July in which the system likely went through a major maintenance. . Special vertically pointing measurements are obtained from the Bisl Mountain dual-polarization radar on 28 June and 11 September 2010. Results show that the bias of differential reflectivity is 0.70dB for these two cases. However, the azimuthal dependence of this bias exists. In addition, these vertically pointing data were used to quantify the statistical uncertainties of dual-pol. parameters and they are compared with the theoretically expected values.

Acknowledgement This study was financially supported by the Construction Technology Innovation Program (08-Tech-Inovation-F01) through the Research Center of Flood Defense Technology for Next Generation in Korea Institute of Construction & Transportation Technology Evaluation and Planning (KICTEP) of Ministry of Land, Transport and Maritime Affairs(MLTM).