POLARIMETRIC RADAR MEASUREMENTS OF RAINFALL COMPARED WITH GROUND-BASED RAIN GAUGES DURING MAYPOLE 84

Estimates of rainfall rates using data from an S-band radar and applying the differential reflectivity technique (RZDR) and two Z-R relationships (Marshall-Palmer RMP and Jones’s thunderstorm RJ) were compared with tipping-bucket rain-gauge measurements at two locations during a rainfall event on June 16, 1984 near Boulder, Colorado. The horizontal and vertical transport of raindrops were taken into account by utilizing an estimated storm speed and direction and average fall time of the raindrops. This procedure was adopted so the time-averaging performed on the rain-gauge measurements would match the spatial averaging of the radar measurements. Corrections were also made in the times of the radar-derived rainfall rates to account for the altitude of the measurements. The results indicate that the differential reflectivity technique performed consistently well at both sites, whereas the Z-R relationships performed well at one site and not as well at the other. The biases and standard errors for the combination of the measurements at both sites were +11% (overestimated by radar) and 38% for RZDR, -13% (underestimated by radar) and 45% for RMP and -24% and 45% for RJ, respectively. © 1990 IEEE