Radar returns from ground clutter in a spectral interval -0.5 to +0.5 m s-1 are studied before applying ground clutter filters. The mean powers of these signals in the polarimetric channels exhibit weak time variations and can be used to monitor stability of a radar system in fair weather. If the radars are in a good technical state, the variations of mean clutter powers in the channels are within ±1 dB and ZDR values are within an interval of ±0.1 dB. These variations weakly depend on temperature and the wind near the ground. Therefore these signals can be used for continuous monitoring of radar calibration. This approach could be used to verify the calibration procedures in radars having built-in equipment (WSR-88Ds) and in radars without such equipment.
Examples of deviations in the mean signal parameters from ground clutter caused by radar hardware issues are discussed. It is shown that a wet radar radome decreases the mean power from ground clutter and increases its ZDR. Correlation between the power drop and the rain rate on the radar site is demonstrated, which is attributed to attenuation of the radar signal for a wet radome. The drop in signal from ground clutter could be used to estimate a decrease in Z from weather objects.