Detection and Characterization of Polarimetric Radar Bright Band Signatures in Northern Taiwan

Abstract

A dual-polarization measurement (DPM) profile simulation was developed and applied to four years of S-band polarimetric radar observations in northern Taiwan to obtain and investigate bright band (BB) features. The algorithm exploits the BB signatures from high elevation angle radar data ( $\ge 6^{\circ }$ ) in cross-correlation coefficient ( $\rho _{\text {hv}}$ ), differential reflectivity ( $Z_{\text {dr}}$ ), and reflectivity (Z) to obtain BB features such as intensity (I), thickness (T), and peak height (H). A key advantage of the proposed algorithm is its ability to detect BB signatures both spatially across azimuthal directions and vertically across elevation angles over time, facilitating a composited optimal H map. Validation against radiosonde data indicates good agreement in estimated H values, with an averaged mean difference (MD) of ~0.2 km. The algorithm effectively detects BB signatures in northern Taiwan, using DPMs as reliable indicators for ML identification, demonstrated in a cold front case study by capturing the transition H from 4 to 2 km. Climatological trends in T and I showed elevation angle dependence, while H remains largely independent of elevation angle. Seasonal trends indicate that H is highest in November and lowest in February and March, which corresponds with radiosonde data, while T and I exhibit minimal seasonal variation.