Experimental Determination of C-Band Radar Attenuation Correction in Melting Ice

Attenuation correction due to rain is well-documented in the literature, where measurements of differential propagation phase (Φdp) are utilized to estimate the path-integrated attenuation (PIA). However, correcting attenuation caused by partially melted ice hydrometeors is challenging as we don't know the scaling coefficient to use to estimate specific attenuation from Φdp. In this study, we have designed an experiment to determine and correct the attenuation of C-band radar signals caused by partially melted ice hydrometeors using a network-based approach. We leverage simultaneous observations from a C-band dual-polarization scanning radar and a vertically pointing S-band profiler radar. The study region is in Huntsville, Alabama where The Atmospheric Radar for Meteorological and Operational Research (ARMOR) C-band radar is located. The S-band profiler radar, maintained by the NOAA Physical Sciences Laboratory (PSL), is also located in this region, approximately 50 kilometers west of the ARMOR radar site. The analysis focuses on a convective storm event that occurred on December 11, 2021. Within the squall line region of the storm, partially melted ice particles significantly attenuated the radar signal at C-band, leading to reduced reflectivity (Z). It was found that correcting for rain-induced attenuation alone was insufficient to account for the pronounced attenuation caused by melting ice hydrometeors. Thus, this study proposes a new attenuation correction methodology that specifically addresses the impact of melting ice hydrometeors. To achieve this, profiles of specific differential propagation phase (Kdp) were examined to identify range gates contaminated by ice particles, and a relationship between specific attenuation (Ah) and Kdp was developed. A piecewise attenuation correction procedure was implemented to separately address regions of rain and melting ice hydrometeors. Validation of this new correction technique involved comparing vertical reflectivity profiles from the C-band radar and the S-band profiler radar. Both instruments were matched spatially and temporally despite their different viewing geometries. The results indicate that this new approach significantly enhances the correlation between profiler measurements and the attenuation-corrected radar reflectivity from the C-band radar.