Thursday, 29 September 2011
Grand Ballroom (William Penn Hotel)
Until recently, the focus of most efforts in the areas of polarimetric radar applications was primarily on severe warm-season convective storms producing flash floods, large hail, and tornadoes. The role of dual-polarization radar measurements in the detection and short-term forecast of hazardous cold-season weather events such as icing, freezing rain, and heavy snowfall remains to be explored but holds great promise. This study presents an overview of numerous polarimetric signatures in winter storms observed at S, C, and X bands and speculations on their association with different microphysical processes and possible practical utilization. Among signatures being discussed are the layers of differential reflectivity Zdr enhancement associated with dendritic growth above the freezing level and refreezing of supercooled raindrops in the subfreezing atmospheric layer below the melting layer in the presence of elevated temperature inversion. The latter signature likely manifests transition from freezing rain to sleet / ice pellets. Other interesting features include Zdr plums and radial streaks of positive and negative Zdr which are related to weak updrafts and possible presence of supercooled water.
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