Quantitative interpretation of precipitation radar measurements at VHF band

Quantitative interpretation of precipitation measurements in the VHF band implies the extraction of the precipitation signal out of the full power spectra, as well as the proper conversion of this signal into reflectivity factors. For this study, we utilize simultaneous observations of co-located vertically pointing radars, operating in the VHF and X bands, as well as drop-size-distribution measurements at the ground. A precipitation event is examined, which corresponds to the passage of the remnants of hurricane Frances over Montreal. The difficulties in analyzing snow signals are highlighted, and rain analysis are performed as an alternative. After expressing the VHF measurements in correct units of power (i.e., the VHF radar calibration, also submitted as Poster presentation), we isolate the rain signal from the recorded VHF power-spectra (which also includes clear-air scattering and specular reflections). We then obtain the average equivalent reflectivity factor under the usual assumptions (i.e., reflectivity constant within the sampling volume). Numerical simulations of rain reflectivity-factors in the VHF band are obtained from high-resolution X-band reflectivity factors, using ground drop-size-distribution measurements to compensate for X-band attenuation. Comparison of these simulations with the corresponding observations indicates good agreement and validates our analysis methods.