Attempts to observe polarimetric signatures of riming in stratiform precipitation

This study attempts to observe polarimetric signatures of riming in stratiform precipitation events using a combination of vertically pointing Doppler X-band and scanning polarimetric S-band radars. Using the X-band radar, cases can be separated into one of three groups: non-riming, riming with no bimodal spectra, and riming with bimodal velocity spectra. By averaging polarimetric variables over a 20◦ by 15 km box, different signatures were documented for each of the three groups. These polarimetric signatures were then verified using a simplified T-matrix scattering model. ZDR was the one polarimetric variable to consistently vary across all three groups. Non-riming cases had profiles of polarimetric signatures similar to numerous previous studies. Riming cases without a bimodal spectra had ZDR values up to 0.2 dB lower than non-riming cases. Cases with a bimodal spectra had ZDR values up to 0.4 dB higher than non-riming cases. While these signatures show the potential to identify riming, they are not significantly larger than systematic biases to be confidently used as without the presence of additional verification such as a vertically pointing radar.