Calibration of the Polarimetric NEXRAD Radar Using Meteorological Signals

Accurate calibration of Z and ZDR is necessary for several hydrological applications and data quality procedures with stringent standards. The idea of polarimetric self-consistency in the rain medium is tested for Z calibration and the polarimetric properties of dry snow aggregates are used for ZDR calibration. The self-consistency calibration is performed using an area-time integral over a sufficiently large spatial/temporal domain with two representative consistency relations for central Oklahoma. ZDR calibration implies polarimetric identification of the melting layer, and subsequent analysis of ZDR above the melting layer in regions of aggregated snow.

Both calibration procedures are implemented in real-time and have been tested using a large dataset collected during JPOLE. The calibration routines operate continuously for the standard VCP during data acquisition and processing. Preliminary analysis suggests that Z can be calibrated with an accuracy of 1 – 1.5 dBZ, and ZDR with the accuracy of 0.2 dB.