On the Use of Ground Return Targets for Radar Reflectivity Factor Calibration Checks

Abstract

In order to use radar quantitatively, each component of a radar system must be measured or calibrated correctly. This paper reports the results of investigations into the use of ground return signals for checks on the calibration of the National Hail Research Experiment's 10 cm radar. Individual ground targets provided returns which were found stable to within about 1 dB; they are thus potentially quite good for calibration checks with many radar systems. Unfortunately, changes in the mode of operation of NHRE's radar made use of this potential unrealizable. A statistical approach was developed using numerous ground targets (294 pairs) which showed at the same locations in both 1972, a year for which reflectivity errors were suspected, and 1974, a year when our radar reflectivity factor measurements were correct. This procedure showed that the 1972 radar reflectivity factors were low by 7.7 dB with a standard deviation of 8.7 dB and a standard error of estimate of the mean of 0.5 dB; this difference was statistically significant at better than the 0.01% level.