Application of Dual-Polarization Radar Melting-Layer Detection Algorithm

A polarimetric melting-layer detection algorithm developed for an S-band radar has been modified for use by the King City C-band radar in southern Ontario, Canada. The technique ingests radar scan volume data to determine the melting-layer top and bottom and to diagnose temporal and spatial variations of the melting-layer heights. The thickness of the melting layer is also derived from the algorithm. Detailed case studies of two frontal systems over this region are described, comparing the radar-derived melting-layer height with aircraft measurement of the height of the 0 degrees C isotherm. The analysis demonstrated the ability to detect rapidly changing melting-layer heights during frontal passages in the region. A range of melting-layer heights for a 3-yr period was investigated and produced detections from close to the ground up to about 5.0 km. Comparison of algorithm results to output from a numerical weather prediction model over the 3-yr period showed good agreement. The correlation coefficient of the heights of the 0 degrees C wet-bulb temperature with the radar-derived melting-layer tops was 0.96. The time series of the algorithm output was used to detect frontal passages and showed that the algorithm should be useful for approximately 19 frontal passages per year in this region.