Rain estimation using X-band dual-polarimetric radar by correcting attenuation

One of issues in estimating rainfall from X-band radar is attenuation caused by rain. This issue can be solved by dual-pol measurements. The path-integrated attenuation are directly related with the propagation phase shift. The path-integrated differential attenuation are directly related with the path-integrated attenuation. Thus the accuracy of radar rain estimation can be improved by attenuation correction using the propagation phase shift. The observed differential phase contains the backscatter phase shift as well as the propagation phase shift. Therefore the backscatter phase shift should be eliminated to estimate rainfall accurately. It is removed by applying FIR filter to the observed differential phase and then the path-integrated attenuation and the path-integrated differential attenuation are calculated using the relationships derived from observed drop size distributions in Korea in order to minimize errors due to variation of these relationship. The reflectivity and the differential reflectivity are corrected by the path-integrated attenuation and the path-integrated differential attenuation respectively. For verification of improvement of accuracy in rain estimation by attenuation correction, comparison between rain accumulation from radar and raingauges is performed. The results show that attenuation correction algorithm using the propagation phase shift leads to significant improvements of accuracy in rain estimation.

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).