The 29 June 2000 Supercell Observed during STEPS. Part II: Lightning and Charge Structure

Abstract

This second part of a two-part study examines the lightning and charge structure evolution of the 29 June 2000 tornadic supercell observed during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). Data from the National Lightning Detection Network and the New Mexico Tech Lightning Mapping Array (LMA) are used to quantify the total and cloud-to-ground (CG) flash rates. Additionally, the LMA data are used to infer gross charge structure and to determine the origin locations and charge regions involved in the CG flashes. The total flash rate reached nearly 300 min−1 and was well correlated with radar-inferred updraft and graupel echo volumes. Intracloud flashes accounted for 95%–100% of the total lightning activity during any given minute. Nearly 90% of the CG flashes delivered a positive charge to ground (+CGs). The charge structure during the first 20 min of this storm consisted of a midlevel negative charge overlying lower positive charge with no evidence of an upper positive charge. The charge structure in the later (severe) phase was more complex but maintained what could be roughly described as an inverted tripole, dominated by a deep midlevel (5–9 km MSL) region of positive charge. The storm produced only two CG flashes (both positive) in the first 2 h of lightning activity, both of which occurred during a brief surge in updraft and hail production. Frequent +CG flashes began nearly coincident with dramatic increases in storm updraft, hail production, total flash rate, and the formation of an F1 tornado. The +CG flashes tended to cluster in or just downwind of the heaviest precipitation, which usually contained hail. The +CG flashes all originated between 5 and 9 km MSL, centered at 6.8 km (−10°C), and tapped LMA-inferred positive charge both in the precipitation core and (more often) in weaker reflectivity extending downwind. All but one of the −CG flashes originated from >9 km MSL and tended to strike near the precipitation core.

On Polarimetric Radar Signatures of Deep Convection for Model Evaluation: Columns of Specific Differential Phase Observed during MC3E*

“…Multiple studies have confirmed and elaborated on the relationship between lightning activity and multi-Doppler radar derived updrafts (Lang and Rutledge 2002;Tessendorf et al 2007b,a;Deierling and Petersen 2008;Calhoun et al 2013) and several have investigated the relationships between polarimetric variables and electrical activity in deep convection storms (Carey and Rutledge 1998;Tessendorf et al 2005;Wiens et al 2005;Bruning et al 2007;Lund et al 2009;Payne et al 2010;Griffin et al 2014). (Heistermann et al 2015).…”

“…As stated in Sec. 1B, results from Wiens et al (2005) suggest that better correlation is found between convection storm statistics (such as updrafts) and flashes, rather than VHF sources. Clustering of VHF source into flashes was performed as suggested by MacGorman et al (2008), with thresholds of 3 km and 0.25 s set for inclusion of a VHF source into a flash, and a minimum of 10 VHF sources required per flash.…”

“…Graupel is produced in regions where riming growth is dominant, in other words, regions of deep convection updrafts. Studies, for example, Deierling and Petersen (2008) have confirmed a strong link between updraft volume and total flash rate in storm systems, with Wiens et al (2005) stressing the importance of using flash density, rather than raw VHF source density, as a measure of lightning activity.…”

On the relationships between lightning frequency and thundercloud parameters of regional precipitation systems

“…More basically, vigorous updrafts are necessary to support the existence of graupel and supercooled liquid droplets in the charging zone. Indeed, strong updrafts have been proposed as a good indicator of lightning [Zipser and Lutz, 1994] and the updraft-lightning relationships in specific regimes have further been quantitatively examined [Lang and Rutledge, 2002;Tessendorf et al, 2005;Wiens et al, 2005;.…”

Characteristics of Lightning Jumps Associated with a Tornadic Supercell on 2 September 2013

“…Gatlin and Goodman (2010) reported that the increasing rate of TFR (6.8 flashes min present study are similar to those reported in previous studies, while the variability of those in severe storms is apparent. Wiens et al (2005) and Tessendorf (2009) suggested that it is better to focus on the general order of magnitude and trend of the flash rate because the quantitative flash rate depends on the specifications of the observational system and the mapping algorithms. Goodman et al (2005) documented that CGFRs increased 15−20 min before a supercell tornado in Tennessee, but that the CGFRs showed a significant lull 5−10 min before tornadogenesis.…”