144 Correction of Radar Reflectivity in Partial Beam Blockage Regions of S-band Dual-Polarization Radar

Wednesday, 16 September 2015
Oklahoma F (Embassy Suites Hotel and Conference Center )
Sung-Hwa Jung, KMA, Seoul, Korea, Republic of (South); and G. Lyu, G. Lee, K. E. Kim, and M. K. Suk

Radar beam blockage caused by terrain, tree and manmade structures limits radar coverage and leads to biases in radar measurements at low elevation angles. This study aims to develop the correction technique for radar reflectivity in partial beam blockage (PBB) regions based on self-consistency principle between intensity and phase measurements from dual-polarization radar. The proposed method utilizes KDP-ZH relationship (KDP=3.77×10-5 ZH0.9) as determined from scattering simulation for S-band using DSDs in Korea.

To remove ground echoes and non-meteorological echoes, the simple and fast procedure was applied using the radial texture of ZH, ZDR, ΦDP, ρhv, and threshold of ρhv (> 0.98). To alleviate contamination from bright band, radar coverage is limited below melting layer that is determined via combination of 0°C isotherm height from radiosonde measurements and morphologic bottom height of bright band in quasi-vertical profile of reflectivity. The system bias of ZH (=-4.41dB in this study) is then calibrated by self-consistency principle using entire volume scans. The blockage bias of ZH in PBB is calculated at each ray using measured ΦDPDP_obs) and calculated ΦDPDP_cal) by integrating of calibrated ZH along radial direction. Concretely, the PBB bias of ZH is derived from the slope between ΦDP_obs and ΦDP_cal. To improve the accuracy of PBB bias, both ΦDP_obs and ΦDP_cal larger than 3° are used.

The performance of the propopsed method is evaluated by comparing with rainfall rain gauges. After applying the proposed method, the significant increases of radar rainfall in the blocked radials were found. The relative error was also reduced in the blocked radials. The correlation coefficient and bias ratio increased from 0.85 to 0.88 and from 0.71 to 0.77, respectively. The standard deviation and normalized standard deviation decreased from 1.82 mmhr-1 to 1.58 mmhr-1 and from 0.50 to 0.43, respectively.

Acknowledgments

This research is supported by “Development and application of Cross governmental dual-pol radar harmonization (WRC-2013-A-1)” project of the Weather Radar Center, Korea Meteorological Administration.

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