Correction for Rain Path Specific and Differential Attenuation of X-Band Dual-Polarization Observations

The accuracy of attenuation correction for X-band reflectivity (Z _H) and differential reflectivity (Z_DR) measurements in rainfall is analyzed using coincident X-band and S-band polarimetric radar observations collected during the International H₂O Project in the period of May-June 2002 at northwestern Oklahoma. Two distinct attenuation correction techniques that use the differential propagation phase shift (Phi_DP) information, which is not a power-dependent measurement, as a means to provide independent estimates of path-integrated attenuation are assessed. The study is facilitated by nonattenuated X-band Z_H and Z_DR profiles simulated based on raindrop size distribution parameters retrieved from matched multiparameter (Z_H, Z_DR, and K_DP) S-band observations. The major outcome of this assessment is that Phi_DP-based attenuation correction for both techniques can reach almost unbiased measurements (within 5% mean relative error) and low random error (15-20% relative standard deviation). The study shows moderate differences in the error statistics of the evaluated techniques. The sensitivity of attenuation correction uncertainty with respect to the assumed variability in raindrops´ oblateness-size relation and the noise in Phi_DP measurement is also shown