Polarimetric And Electrical Structure Of The 19 May 2013 Edmond-Carney, Oklahoma, Tornadic Supercell

SIGNIFICANCE STATEMENT: Lightning is a manifestation of collisions between hydrometeor species, especially ice crystals and graupel. There still exist gaps in our understanding of the physical processes that link macroscopic properties of storms and their electrification characteristics. This study exploits dual-polarization radar signatures to characterize the temporal variability in the microphysical and electrical properties of a tornadic supercell. This particular storm maintained an inverted polarity charge structure throughout its mature phase. Pulses in the storm's updraft (inferred from behavior of differential reflectivity columns) were associated with jumps in lightning flash rates. Finally, we show that the time variations in lightning activity can be explained by changes in differential reflectivity column volume and height.We demonstrate the utility of transient polarimetric signatures (Z(DR) and K-DP columns, a proxy for surges in a thunderstorm updraft) to explain variability in lightning flash rates in a tornadic supercell. Observational data from a WSR-88D and the Oklahoma lightning mapping array are used to map the temporal variance of polarimetric signatures and VHF sources from lightning channels. It is shown, via three-dimensional and cross-sectional analyses, that the storm was of inverted polarity resulting from anomalous electrification. Statistical analysis confirms that mean flash area in the Z(DR) column region was 10 times smaller than elsewhere in the storm. On an average, 5 times more flash initiations occurred within Z(DR) column regions, thereby supporting existing theory of an inverse relationship between flash initiation rates and lightning channel extent. Segmentation and object identification algorithms are applied to gridded radar data to calculate metrics such as height, width, and volume of Z(DR) and K-DP columns. Variability in lightning flash rates is best explained by the fluctuations in Z(DR) column volume with a Spearman's rank correlation coefficient value of 0.72. The highest flash rates occur in conjunction with the deepest Z(DR) columns (up to 5 km above environmental melting level) and largest volumes of Z(DR) columns extending up to the -20 degrees C level (3 km above the melting level). Reduced flash rates toward the end of the analysis are indicative of weaker updrafts manifested as low Z(DR) column volumes at and above the -10 degrees C level. These findings are consistent with recent studies linking lightning to the interplay between storm dynamics, kinematics, thermodynamics, and precipitation microphysics.