Correction of X-band radar reflectivity and differential reflectivity for rain attenuation using differential phase

Rain attenuation correction is very important to obtain accurate radar reflectivity (ZH) and differential reflectivity (ZDR), particularly with the X-band wavelength radar. In the case of a dual-polarized radar, ZH and ZDR can easily be corrected by differential phase (ΦDP) measurements. In the self-consistent method with constraints proposed by Bringi et al. [Bringi, V.N., Keenan, T.D., and Chandrasekar, V., 2001. Correcting C-band radar reflectivity and differential reflectivity data for rain attenuation: a self-consistent method with constraints. IEEE Trans. Geosci. Remote Sens. 39, 1906–1915.], the relationship AH = αKDPb (where AH is the specific attenuation and KDP is the specific differential phase) is shown to be almost linear and the coefficient α is determined by employing a minimization process for each beam of the radar. However, α can be varied along the path length (r0 ~ r) in the same precipitation system since α depends on the temperature and raindrop size distribution (DSD).The correction algorithm is modified to obtain the optimum α distribution for the relationship AH = α KDPb, and it is applied to the multiparameter X-band-wavelength (MP-X) radar operated by the National Research Institute for Earth Science and Disaster Prevention (NIED) in Japan. The optimum α is distributed over a wide range from 0.16 to 0.76 dB deg− 1 with a 1.5 km resolution. The reconstructed ΦDP by using the optimum α shows a good agreement with the measured ΦDP during the validation. Moreover, the corrected relationships between KDP–ZH, AH–ZH, ZDR–ZH, and ZDP–ZH are also similar to the theoretical values predicted by scattering simulations [Park, S.-G., Bringi, V.N., Chandrasekar, V., Maki, M., and Iwanami, K., 2005a. Correction of radar reflectivity and differential reflectivity for rain attenuation at X-band. Part I: theoretical and empirical basis. J. Atmos. Ocean. Technol. 22, 1621–1632.]. The proposed new algorithm in this study could be used and effectively adapted to estimate rainfall amounts with more accuracy.