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

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 angles radar data (≥ 6◦) in cross-correlation coefficient (ρ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">hv</i>), differential reflectivity (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z_dr</i>), and reflectivity (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i>) to obtain BB features such as intensity (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i>), thickness (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i>), and peak height (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i>). 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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> map. Validation against radiosonde data indicates good agreement in estimated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> values, with an averaged mean difference 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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> from 4 km to 2 km. Climatological trends in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> showed elevation angle dependence, while <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> remains largely independent of elevation angle. Seasonal trends indicate that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> is highest in November and lowest in February and March, which corresponds with radiosonde data, while <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> exhibit minimal seasonal variation.