The Relationships between Parameters of C-Band Dual Polarization Radar and Their Calibration Issues

The relationships between the parameters of C-band dual polarimetric radar, and the change ranges and distributions of the coefficients in the relationships are analyzed in detail based on numerical simulation with the assumption of gamma drop size distribution (DSD) and the average diameter of raindrops smaller or larger than 1.5 mm. To the relationship between reflectivity ZH and differential reflectivity ZDR, the coefficients have great change ranges whichever linear or quadratic fitting. There are a good linear relationship between ZH and logarithmic specific differential phase log (KDP), and the coefficients in the relationship between ZH, ZDR, and log (KDP) are relative stable for actual cases measurements. However, all these relationships can be obviously influenced by the DSD. In addition, these relationships are verified with actual data collected using three disdrometers, and the fitting coefficients show that there are a good consistency between the simulation and measurement data. The relationship between ZH, ZDR, and log (KDP) fitted by DSD of small raindrop is further applied as a self-consistency method to the calibration of ZH in two cases, and have achieved quite well effect.

The general ZDR calibration methods were verified by the actual data, the results suggest that vertical sounding, sun scan, and elevation methods are not suitable to the operational radar for some reasons. The micro-raindrop and dry snow methods are stable, and can be regarded as proper methods in the ZDR calibration in practical application.