Radar calibration using polarimetric observations

While radar polarization diversity has shown improvements in data quality and hydrometeor classification, the accuracy in estimating rainfall remains limited by the calibration of the radar. This study serves as a template to illustrate how differential reflectivity (Z_DR) and reflectivity at horizontal polarization (Z_H) can be calibrated to within 0.1-0.2 dB and better than 1.0 dB respectively. Hydrometeor observations at vertical incidence are used to calibrate Z_DR where the intrinsic values are known to be 0 dB. Calibration of Z_H can be achieved using the relationship between Z_H, Z_DR, and specific differential propagation phase (K_DP). K_DP is calculated from observations of Z_DR and Z_H and then integrated in the radial direction to yield a consistency-based differential propagation phase (Φ_DP). Differences between consistency and observed Φ_DP are attributed to miscalibrated Z_H. A dataset comprised of thousands of radial profiles of polarimetric data collected by MeteoFrance's C-band radar near Trappes is used to calibrate Z_DR and Z_H.