Sensitivity associated with bright band/melting layer location on radar reflectivity correction for attenuation at C-band using differential propagation phase measurements

The modern rain profiling algorithms in reflectivity (ZH) correction for two way path integrated attenuation (AH) using dual polarization radar at attenuating frequencies rely on differential propagation phase (ΦDP) measurements. To retrieve corrected reflectivity profiles from the measured profiles, these algorithms impose an external constraint in the inversion processes which is provided by total differential phase shifts (∆ΦDP) valid for rain cells only. However, there is a possibility of radar beams propagating through and beyond the bright band/melting layer region hence may observe non-rainy cells. In light of this, the present study explores the variation of reflectivity correction in different ∆ΦDP scenarios by varying the rain cells locality by +/− 500 m with respect to the “reference” rain cells location derived from a numerical weather prediction (NWP) model output. To implement this, the well-known ZPHI algorithm from the rain profiling algorithms group is applied to several rainfall events from a C-band dual polarization radar. Before applying the algorithms, a total of 162,415 raindrop spectra have been used to retrieve the algorithm coefficients through T-matrix scattering simulated dual polarized signatures. It is revealed that, in some cases, when the ΦDP profile in an attenuated beam is in increasing gradient near the rain layer top region, there could be a variation of about 1-2 dB in comparison with the “reference” attenuation corrected reflectivity. Such phenomenon is in accord with the reflectivity statistics when comparing with one neighboring C-band single polarization radar derived reflectivity data. Additionally, the remarkable agreement between the reflectivity profiles lends the applicability of the ZPHI algorithm in the attenuation correction with known rain/melting layer information.