260 Comparative Evaluation of Raingauge-Adjusted Radar Rainfall (RAR) with Different Raingauge Process: TRMM-GSP vs WRC-RGP

Thursday, 31 August 2017
Zurich DEFG (Swissotel Chicago)
Sangmi Lee, KMA, Seoul, Korea, Republic of (South); and M. K. Suk, S. H. Jung, and S. K. Lee

The radar rainfall estimation is usually differing from raingauge rainfall due to vertical evolution of precipitation, intrinsic difference between two measurements, different spatio-temporal representativeness. Korea Meteorological Administration (KMA) has developed the adjustment techniques of radar rainfalls based on raingauge measurements, Radar-AWS Rainrate (RAR). In order to provide the gauge-adjusted radar rainfall in real time, RAR system computes new coefficient “a” and exponent “b” in Z-R relationship based on pairs of radar rainfall and raingauge rainfall.
The performance and stability of RAR is subjected to pre-processing of raingauge rainfall. The current RAR system utilizes TRMM-GSP algorithm as pre-processing of raingauge rainfall. The temporal variation of RAR increases at the beginning and the end stages of rainfall due to artificial errors in rainfall from TRMM-GSP algorithm. In this study, we developed the new technique for raingauge process, Weather Radar Center-Rain Gauge Process (WRC-RGP), to replace the existing TRMM-GSP algorithm and improved the rainfall estimation technique by obtaining improved “a” and “b” in Z-R relationship.
For comparative evaluation of new WRC-RGP technique with TRMM-GSP algorithm, from May 2015 to October 2015, the correlation coefficients of raingauge rainfall from WRC-RGP and TRMM-GSP were 0.951 and 0.998, respectively. After applying WRC-RGP algorithm, the biases were significantly reduced from 0.82mmh-1 to 0.01mmh-1 and the root mean square errors (RMSEs) decrease from 0.71mmh-1 to 0.06mmh-1, respectively.
WRC-RGP technique leads to significant improvements of RAR system’s performance. We found that the temporal variation of coefficient “a” and exponent “b” in Z-R relation more suitable when WRC-RGP was applied. And RAR overestimations have been reduced due to stable Z-R relationship. The accuracy of RAR technique has been also improved.
In order to obtain stable and improved “a” and “b”, we will investigate the statistical characteristics of “a” and “b” of Z-R fitting curve in RAR system. We are planning to develop raingauge-adjusted technique for radar rainfall estimation of dual-polarization radar.


The research id 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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