Long-Term Assessment of the Reflectivity Biases and Wet-Radome Effect Using Collocated Operational S- and C-Band Dual-Polarization Radars

Abstract

This study assessed the long-term radar reflectivity (Z) biases of collocated S-and C-band dual-polarization radars. The systematic bias, wet-radome effect (WRE), and attenuation effect were investigated. The algorithm of self-consistency utilizes Z, differential reflectivity (Z dr ), and a specific differential phase (K dp ) to estimate the systematic bias and WRE of both radars. Eleven years of disdrometer data in northern Taiwan were used to obtain the self-consistency and K dp -based attenuation correction relation coefficients. Subsequently, a series of sensitivity tests were conducted to examine the influence of these coefficients on bias and attenuation corrections. The K dp (Z, Z dr ) relationship outperformed that of K dp (Z). The K dp (Z, Z dr ) relationship with seasonal coefficients and systematic bias-corrected Z dr constituted the optimal procedure. The corrected Z of collocated radars was in good agreement, lending further validity to the correction schemes. The results demonstrated that the stable systematic bias values of two radars were −1.89 to −1.14 dB and −2.46 to −1.87 dB. During the WRE period, additional underestimations of Z by nearly 4 and 7 dB were recorded for S-and C-band radars, respectively. The mean value of radar reflectivity near radar (Z nr ) was obtained to identify the WRE period. In this study, an innovative quadratic polynomial fitting equation was proposed to investigate the systematic and WRE biases using Z nr . Moreover, a pronounced wind intensity dependency of the WRE could be observed in the quadratic polynomial fitting equation.