Optimization of the Differential Phase Processing at Different Wavelengths

Differential phase φDP is a key parameter in radar meteorology for estimating precipitation intensity and characterizing the size and shape of hydrometeors. φDP normally behaves as a monotonically increasing function of range within a precipitation shaft. Backscatter differential phase δ contributes to φDP where larger raindrops or mixed phase hydrometeors exist. The δ jump can artificially increase and decrease the φDP gradient along each radial path, which greatly affect specific differential phase KDP calculations, especially at shorter radar wavelengths. In this study, we utilize the C-band radar (C-SAPR2) data collected during Tracking Aerosol Convection Interactions Experiment (TRACER) campaign and nearby S-band WSR-88D radar (KHGX) data to quantify δ at both microwave frequency bands. Radial profiles of δ at both wavelengths are calculated based on modified “ZPHI” method in pure rain and mixed phase rain separately. The quality control based on signal-to-noise ratio and nonuniform beam filling effect has been performed d before any calculations. Subtracting δ from φDP is used to better calculate KDP for rainfall estimation. Comparisons with surface rain gauges in the Houston, TX region of rainfall estimates from the C and S band radars are performed. Our results show that the modified φDP profiles are more suitable for a more accurate KDP and rainfall estimation, particularly in areas of mixed-phase hydrometeors.