Identification of range overlaid echoes using polarimetric radar measurements based on a fuzzy logic approach

The Ministry of Land, Infrastructure and Transport (MOLIT) of South Korea operates two S-band dualpolarimetric radars, as of 2013, to manage water resources through quantitative rainfall estimations at the surface level. However, the radar measurements suffer from range ambiguity. In this study, an algorithm based on fuzzy logic is developed to identify range overlaid echoes using seven inputs: standard deviations of differential reflectivity SD(Z_DR), differential propagation phase SD(φDP), correlation coefficient SD(ρ_HV) and spectrum width SD(σ_ν), mean of ρ_HV and σ_ν, and difference of φ_DP from the system offset Δφ_DP. An examination of the algorithm's performance shows that these echoes can be well identified and that echoes strongly affected by second trip are highlighted by high probabilities, over 0.6; echoes weakly affected have probabilities from 0.4 to 0.6; and those with low probabilities, below 0.4, are assigned as echoes without range ambiguity. Aquantitative analysis of a limited number of cases using the usual skill scores shows that when the probability of 0.4 is considered as a threshold for identifying the range overlaid echoes, they can be identified with a probability of detection of 90%, a false alarm rate of 6%, and a critical success index of 84%.