Calibration of the Polarimetric Nexrad Radar Using Meteorological Signals

Regular operation of weather radar mandates frequent calibration to ensure accurate measurements. Even modest calibration errors in reflectivity factor Z and differential reflectivity ZDR may produce severe deficiencies in the quality of radar products such as rainfall estimates and hydrometeor classes. Radar users, including the Federal Aviation Administration (FAA), rely on high quality weather radar data to ensure efficient operations. Techniques for absolute calibration of Z and ZDR measured with dual-polarization weather radars are examined in this paper. The idea of polarimetric selfconsistency in the rain medium is tested for Z calibration (e.g., Goddard et. al 1994, Scarchilli et al. 1996, Vivekanandan et al. 2003) and the polarimetric properties of natural weather scatterers are used for ZDR calibration (e.g., Gorgucci et al. 1999, Bringi and Chandrasekar 2001). The Z calibration procedure is implemented in real-time and tested using a large dataset collected during the Joint Polarization Experiment (JPOLE). This calibration routine operates continuously for the standard VCP during data acquisition and processing.