Radar calibration using consistency of polarization parameters and constraints for drop shapes

The accuracy of radar-based rain rates is limited by the calibration of radar reflectivity (ZH), which must be measured within 1 dB for rainfall estimates to have an accuracy of 15%. Several approaches to radar calibration have been undertaken which are summarized in Atlas (2002). The receive component of the radar can be calibrated using a transmitter with a known signal strength. Transmit and receive components can be calibrated jointly by positioning a reflective target with a known radar crosssection into the radar beam using aircraft, a balloon, etc. Another approach is to compare radar reflectivity to disdrometer measurements as in Joss et al. (1968). The relative calibrations of the US Weather Service Radar-1988 Doppler (WSR-88Ds) have also been explored by comparisons with space-borne radar (Bolen and Chandrasekar 2000) and neighboring WSR-88D radars (Gourley et al. 2003). None of these approaches has emerged as the standard procedure for calibrating radars.