Rainfall Measurement Error by WSR-88D Radars due to Variations in<i>Z–R</i>Law Parameters and the Radar Constant

Ulbrich, Carlton W.; Lee, L. G.

doi:10.1175/1520-0426(1999)016<1017:rmebwr>2.0.co;2

Cited by 91 publications

(74 citation statements)

References 6 publications

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“…The averaged composition method in the overlapping area of the 10 KMA radars can weaken the rain system locality feature, and as such compensation by the observed rainfall for the rain-gauge position (Makihara 1996) will be considered. In addition, the 1 hour data sampling for the Z-R relationship in RAD-RAR is selected empirically (Ulbrich et al 1999;Fulton 1999), but further studies are required for the optimal temporal resolution of the Z-R relationship. Description in detail of the idea and design of the observing system using radars and rain-gauges would also be of interest if it is well considered under the specific topography, density of the rain-gauge network, deployment of radar systems, and their performance, which also requires further study.…”

Section: Discussionmentioning

confidence: 99%

“…The processing of radar reflectivity data is summarized as follows: 1) radar data is recorded in the volume data every 10 min., 2) radar volume data undergoes quality controls such as the removal of non-precipitation echoes including the spot echo, line echo, sun strobe (non-precipitation echo represented when radar antenna points are aimed directly at the sun), second trip echo, ground clutter, sea clutter (Collier 1996), and anomalous propagation (Battan 1973) by the QC algorithm (Zhang et al 2004), and then 3) the corrected reflectivity gives CAPPI data Vol. 91,No.…”

Section: A Radar Reflectivitymentioning

confidence: 99%

“…4 Jounal of the Meteorological Society of Japan 546 of a 1 km × 1 km grid resolution at an altitude of 1.5 km through the bilinear interpolation method (Mohr and Vaughan 1979). This QC algorithm (Zhang et al 2004) uses the determined threshold of the horizontal smoothness and vertical difference of the reflectivity fields using features of horizontal and vertical distribution and of the occurrence of non-precipitation echoes. When the horizontal smoothness and vertical difference at the given radar gate is not included in the ranges of the precipitation echoes, this gate is considered as a non-precipitation echo and is removed.…”

Section: A Radar Reflectivitymentioning

confidence: 99%

See 2 more Smart Citations

Operational Real-Time Adjustment of Radar Rainfall Estimation over the South Korea Region

Suk

Chang²,

Cha

et al. 2013

Journal of the Meteorological Society of Japan

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An operational real-time adjusted radar-automatic weather station (AWS) rain rate (RAD-RAR) system, using 10 radars of the Korea Meteorological Administration (KMA), has been developed for the South Korea region. The procedure of the RAD-RAR system consists of four steps for real-time operation: 1) the quality control of volumetric reflectivity for each radar, 2) the computation of the rain-gauge rain rate every 10 min. within each radar, 3) the realtime (updated every 10 min.) rainfall estimation by the Z-R relationship minimizing the difference between the 10-min constant altitude plan position indicator and rain-gauge rain rate based on window probability matching method (WPMM) and by the real-time bias correction of RAD-RAR conducted at 10 min. intervals for each radar by making the bias, and 4) the composition of estimated rainfall data of the 10 radars. It is noted that this RAD-RAR system is available only for summer rainfall cases with the absence of bright band around 1.5 km in height, as the system does not include bright band correction. The performance of RAD-RAR was examined for the 10 heavy rainfall events of 2006, and we obtained results suggesting that the real-time Z-R adjustment of RAD-RAR is better in terms of the agreement with the rain-gauge rain rate than that of the previously fixed Z-R relationship, and the additional bias correction of RAD-RAR yields slightly better results. A square of correlation coefficient R 2 = 0.84 was obtained between the daily accumulated observed and RAD-RAR estimated rainfall.

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Section: Discussionmentioning

confidence: 99%

Section: A Radar Reflectivitymentioning

confidence: 99%

Section: A Radar Reflectivitymentioning

confidence: 99%

See 1 more Smart Citation

Operational Real-Time Adjustment of Radar Rainfall Estimation over the South Korea Region

Suk

Chang²,

Cha

et al. 2013

Journal of the Meteorological Society of Japan

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“…Rain was observed on 18 days, and the total number of DSDs equals 1298 samples. Ulbrich et al (1999) carried out a first analysis of the disdrometer data, obtained during the campaign.…”

Section: Disdrometermentioning

confidence: 99%

An attempt to calibrate the UHF strato-tropospheric radar at Arecibo using NexRad radar and disdrometer data

Kafando

Petitdidier²

2004

Ann. Geophys.

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Abstract. The goal of this paper is to present a methodology to calibrate the reflectivity of the UHF Strato-Tropospheric (ST) radar located at NAIC in Puerto Rico. The UHF lower relevant altitude is at 5.9 km, the melting layer being at around 4.8 km. The data used for the calibration came from the observations of clouds, carried out with StratoTropospheric dual-wavelength (UHF and VHF) radars and a disdrometer; those instruments being located on the NAIC site in Arecibo, Puerto Rico. The National Weather Service operates other instruments like the radiosondes and the NexRad Radar in other sites.The proposed method proceeds in two steps. The first consists of the comparison between the NexRad reflectivity and the reflectivity computed from the drop size distributions measured by the disdrometer for one day with a noticeable rainfall rate. In spite of the distance of both instruments, the agreement between the reflectivities of both instruments is enough good to be used as a reference for the UHF ST radar. The errors relative at each data set is found to be 2.75 dB for the disdrometer and 4 dB for the NexRad radar, following the approach of Hocking et al. (2001). The inadequacy between the two sampled volume is an important contribution in the errors.The second step consists of the comparison between the NexRad radar reflectivity and the UHF non-calibrated reflectivity at the 4 altitudes of common observations during one event on 15 October 1998. Similar features are observed and a coefficient is deduced. An offset around 4.7 dB is observed and the correlation factor lies between 0.628 and 0.730. According to the errors of the data sets, the precision on the calibration is of the order of 2 dB. This method works only when there are precipitation hydrometeors above the NAIC site. However, the result of the calibration could be applied to other data obtained during the campaign, the only constraint being the same value of the transmitter power.

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“…Joss et al (1968) calibrated radar reflectivity by using the vertical profile of reflectivity and disdrometer-inferred Z H . The radar reflectivity was calibrated by comparisons between the radar and disdrometer reflectivity to check the calibration of the WSR-88D (weather surveillance radars -1988 Doppler) at Greer, South Carolina (Ulbrich and Lee, 1999). Goddard et al (1982) and Goddard and Cherry (1984) compared radar results with disdrometer results by using the axis-ratio relations of Pruppacher and Beard (1970) and Pruppacher and Pitter (1971), respectively; they found that radar measures of Z DR were 0.3 and 0.1 dB lower than the disdrometer estimates.…”

mentioning

confidence: 99%

Dual-polarization radar rainfall estimation in Korea according to raindrop shapes obtained by using a 2-D video disdrometer

et al. 2016

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Abstract. Polarimetric measurements are sensitive to the sizes, concentrations, orientations, and shapes of raindrops. Thus, rainfall rates calculated from polarimetric radar are influenced by the raindrop shapes and canting. The mean raindrop shape can be obtained from long-term raindrop size distribution (DSD) observations, and the shapes of raindrops can play an important role in polarimetric rainfall algorithms based on differential reflectivity (Z DR ) and specific differential phase (K DP ). However, the mean raindrop shape is associated with the variation of the DSD, which can change depending on precipitation types and climatic regimes. Furthermore, these relationships have not been studied extensively on the Korean Peninsula. In this study, we present a method to find optimal polarimetric rainfall algorithms for the Korean Peninsula by using data provided by both a twodimensional video disdrometer (2DVD) and the Bislsan Sband dual-polarization radar. First, a new axis-ratio relation was developed to improve radar rainfall estimations. Second, polarimetric rainfall algorithms were derived by using different axis-ratio relations. The rain gauge data were used to represent the ground truth situation, and the estimated radar-point hourly mean rain rates obtained from the different polarimetric rainfall algorithms were compared with the hourly rain rates measured by a rain gauge. The daily calibration biases of horizontal reflectivity (Z H ) and differential reflectivity (Z DR ) were calculated by comparing Z H and Z DR radar measurements with the same parameters simulated by the 2DVD. Overall, the derived new axis ratio was similar to the existing axis ratio except for both small particles (≤ 2 mm) and large particles (≥ 5.5 mm). The shapes of raindrops obtained by the new axis-ratio relation carried out with the 2DVD were more oblate than the shapes obtained by the existing relations. The combined polarimetric rainfall relations using Z DR and K DP were more efficient than the single-parameter rainfall relation for estimated 2DVD rainfall; however, the R(Z H , Z DR ) algorithm showed the best performance for radar rainfall estimations, because the rainfall events used in the analysis consisted mainly of weak precipitation and K DP is relatively noisy at lower rain rates (≤ 10 mm h −1 ). Some of the polarimetric rainfall algorithms can be further improved by new axis-ratio relations.

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Rainfall Measurement Error by WSR-88D Radars due to Variations inZ–RLaw Parameters and the Radar Constant

Cited by 91 publications

References 6 publications

Operational Real-Time Adjustment of Radar Rainfall Estimation over the South Korea Region

Operational Real-Time Adjustment of Radar Rainfall Estimation over the South Korea Region

An attempt to calibrate the UHF strato-tropospheric radar at Arecibo using NexRad radar and disdrometer data

Dual-polarization radar rainfall estimation in Korea according to raindrop shapes obtained by using a 2-D video disdrometer

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