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 ZH and ZDR 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.