Dual-polarimetric radar characteristics of convective-wind-producing thunderstorms over Kennedy Space Center
Scholten, Cort A.
The dual-polarimetric upgrade of the Weather Surveillance Radar in Melbourne, Florida, has provided the opportunity to expand the study of thunderstorms over Kennedy Space Center and Cape Canaveral Air Force Station (KSC/CCAFS). This extends a series of previous climatological and radar studies of warm-season thunderstorms (May through September) over KSC/CCAFS, with the ultimate goal of improving convective wind warnings. With the ability now to measure relative horizontal and vertical dimensions of hydrometeors and their conforming behavior within a radar pulse volume, interpretations can be made about the type of precipitation and therefore some intra-storm dynamics. Differential reflectivity (ZDR), correlation coefficient (ρHV), and specific differential phase shift (KDP) were the dual-polarimetric products examined. Studies have shown each of the three products exhibit signatures that correspond with precipitation-laden convective updrafts. The signatures of ZDR columns, ρHV melting layer lofting, and KDP columns were investigated within central Florida warm-season convection. ZDR columns and KDP columns occurred regularly in the convective cases studied. ρHV melting layer signatures were generally unable to be identified because of the chaotic and small-scale nature of the minimally sheared convection. Except for occasional reductions in ρHV values within hail cores, ρHV was not a reliable indicator of convective updrafts in Florida. Twenty convective cells from 2012, identified as likely being responsible for near-surface wind gusts measured by the KSC/CCAFS wind tower network, were used to explore the relationship between the magnitudes of the radar updraft signatures and the strength of the peak wind gusts from the resulting downdraft. The maximum height and intensity of KDP columns, maximum height of ZDR columns, and maximum height of ≥50dBZ reflectivity echoes during the cell's life cycle were compared to the strength of subsequent wind gust. Correlations were very poor, with regression-squared values <0.16, and some <0.01.The reasons for poor correlations are numerous, and can be sorted into three main categories: (1) physical limitations and environmental condition uncertainties, (2) radar data quality and resolution challenges, and (3) errors from manual interrogation techniques. Despite the inauspicious results, a discussion of these challenges opens up many avenues for additional studies that focus on specific problems and use stricter constraints.