Lightning Activity in a Hail-Producing Storm Observed with Phased-Array Radar

2011 ◽  
Vol 139 (6) ◽  
pp. 1809-1825 ◽  
Author(s):  
C. Emersic ◽  
P. L. Heinselman ◽  
D. R. MacGorman ◽  
E. C. Bruning
Keyword(s):  
Phased Array ◽  
Velocity Structure ◽  
Negative Charge ◽  
Positive Charge ◽  
Lightning Activity ◽  
Mature Stage ◽  
Charge Structure ◽  
Phased Array Radar ◽  
Lightning Detection ◽  
Mapping Array

Abstract This study examined lightning activity relative to the rapidly evolving kinematics of a hail-producing storm on 15 August 2006. Data were provided by the National Weather Radar Testbed Phased-Array Radar, the Oklahoma Lightning Mapping Array, and the National Lightning Detection Network. This analysis is the first to compare the electrical characteristics of a hail-producing storm with the reflectivity and radial velocity structure at temporal resolutions of less than 1 min. Total flash rates increased to approximately 220 min−1 as the storm’s updraft first intensified, leveled off during its first mature stage, and then decreased for 2–3 min despite the simultaneous development of another updraft surge. This reduction in flash rate occurred as wet hail formed in the new updraft and was likely related to the wet growth; wet growth is not conducive to hydrometeor charging and probably contributed to the formation of a “lightning hole” without a mesocyclone. Total flash rates subsequently increased to approximately 450 min−1 as storm volume and inferred graupel volume increased, and then decreased as the storm dissipated. The vertical charge structure in the storm initially formed a positive tripole (midlevel negative charge between upper and lower positive charges). The charge structure in the second updraft surge consisted of a negative charge above a deep midlevel positive charge, a reversal consistent with the effects of large liquid water contents on hydrometeor charge polarity in laboratory experiments. Prior to the second updraft surge, the storm produced two cloud-to-ground flashes, both lowering the usual negative charge to ground. Shortly before hail likely reached ground, the storm produced four cloud-to-ground flashes, all lowering the positive charge. Episodes of high singlet VHF sources were observed at approximately 13–15 km during the initial formation and later intensification of the storm’s updraft.

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

2005 ◽  
Vol 62 (12) ◽  
pp. 4151-4177 ◽  
Author(s):  
Kyle C. Wiens ◽  
Steven A. Rutledge ◽  
Sarah A. Tessendorf
Keyword(s):  
Positive Charge ◽  
Lightning Activity ◽  
Structure Evolution ◽  
Severe Thunderstorm ◽  
Charge Structure ◽  
Flash Rate ◽  
Lightning Detection ◽  
Mapping Array ◽  
Total Lightning ◽  
Mexico Tech

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.

scholarly journals Electrical and Polarimetric Radar Observations of a Multicell Storm in TELEX

2007 ◽  
Vol 135 (7) ◽  
pp. 2525-2544 ◽  
Author(s):  
Eric C. Bruning ◽  
W. David Rust ◽  
Terry J. Schuur ◽  
Donald R. MacGorman ◽  
Paul R. Krehbiel ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Negative Charge ◽  
Positive Charge ◽  
Three Dimensional ◽  
Phase Region ◽  
Polarimetric Radar ◽  
Radar Observations ◽  
Mapping Array ◽  
Lightning Initiation

Abstract On 28–29 June 2004 a multicellular thunderstorm west of Oklahoma City, Oklahoma, was probed as part of the Thunderstorm Electrification and Lightning Experiment field program. This study makes use of radar observations from the Norman, Oklahoma, polarimetric Weather Surveillance Radar-1988 Doppler, three-dimensional lightning mapping data from the Oklahoma Lightning Mapping Array (LMA), and balloon-borne vector electric field meter (EFM) measurements. The storm had a low flash rate (30 flashes in 40 min). Four charge regions were inferred from a combination of LMA and EFM data. Lower positive charge near 4 km and midlevel negative charge from 4.5 to 6 km MSL (from 0° to −6.5°C) were generated in and adjacent to a vigorous updraft pulse. Further midlevel negative charge from 4.5 to 6 km MSL and upper positive charge from 6 to 8 km (from −6.5° to −19°C) were generated later in quantity sufficient to initiate lightning as the updraft decayed. A negative screening layer was present near the storm top (8.5 km MSL, −25°C). Initial lightning flashes were between lower positive and midlevel negative charge and started occurring shortly after a cell began lofting hydrometeors into the mixed phase region, where graupel was formed. A leader from the storm’s first flash avoided a region where polarimetric radar suggested wet growth and the resultant absence of noninductive charging of those hydrometeors. Initiation locations of later flashes that propagated into the upper positive charge tracked the descending location of a polarimetric signature of graupel. As the storm decayed, electric fields greater than 160 kV m−1 exceeded the minimum threshold for lightning initiation suggested by the hypothesized runaway breakdown process at 5.5 km MSL, but lightning did not occur. The small spatial extent (≈100 m) of the large electric field may not have been sufficient to allow runaway breakdown to fully develop and initiate lightning.

scholarly journals Simulated Electrification of a Small Thunderstorm with Two-Moment Bulk Microphysics

2010 ◽  
Vol 67 (1) ◽  
pp. 171-194 ◽  
Author(s):  
Edward R. Mansell ◽  
Conrad L. Ziegler ◽  
Eric C. Bruning
Keyword(s):  
Charge Separation ◽  
Negative Charge ◽  
Positive Charge ◽  
Model Simulation ◽  
Particle Density ◽  
Phase Region ◽  
Number Concentration ◽  
Ice Crystals ◽  
Microphysics Scheme ◽  
Charge Structure

Abstract Electrification and lightning are simulated for a small continental multicell storm. The results are consistent with observations and thus provide additional understanding of the charging processes and evolution of this storm. The first six observed lightning flashes were all negative cloud-to-ground (CG) flashes, after which intracloud (IC) flashes also occurred between middle and upper levels of the storm. The model simulation reproduces the basic evolution of lightning from low and middle levels to upper levels. The observed lightning indicated an initial charge structure of at least an inverted dipole (negative charge above positive). The simulations show that noninductive charge separation higher in the storm can enhance the main negative charge sufficiently to produce negative CG flashes before upper-level IC flashes commence. The result is a “bottom-heavy” tripole charge structure with midlevel negative charge and a lower positive charge region that is more significant than the upper positive region, in contrast to the traditional tripole structure that has a less significant lower positive charge region. Additionally, the occurrence of cloud-to-ground lightning is not necessarily a result of excess net charge carried by the storm, but it is primarily caused by the local potential imbalance between the lowest charge regions. The two-moment microphysics scheme used for this study predicted mass mixing ratio and number concentration of cloud droplets, rain, ice crystals, snow, and graupel. Bulk particle density of graupel was also predicted, which allows a single category to represent a greater range of particle characteristics. (An additional hail category is available but was not needed for the present study.) The prediction of hydrometeor number concentration is particularly critical for charge separation at higher temperatures (−5° < T < −20°C) in the mixed phase region, where ice crystals are produced by rime fracturing (Hallett–Mossop process) and by splintering of freezing drops. Cloud droplet concentration prediction also affected the rates of inductive charge separation between graupel and droplets.

scholarly journals Formation of Charge Structures in a Supercell

2010 ◽  
Vol 138 (10) ◽  
pp. 3740-3761 ◽  
Author(s):  
Eric C. Bruning ◽  
W. David Rust ◽  
Donald R. MacGorman ◽  
Michael I. Biggerstaff ◽  
Terry J. Schuur
Keyword(s):  
Electric Field ◽  
Conceptual Model ◽  
Negative Charge ◽  
Positive Charge ◽  
Radar Data ◽  
Opposite Polarity ◽  
Charge Structure ◽  
Precipitation Region ◽  
Normal Polarity ◽  
The Right

Abstract Lightning mapping, electric field, and radar data from the 26 May 2004 supercell in central Oklahoma are used to examine the storm’s charge structure. An initial arc-shaped maximum in lightning activity on the right flank of the storm’s bounded weak echo region was composed of an elevated normal polarity tripole in the region of precipitation lofted above the storm’s weak echo region. Later in the storm, two charge structures were associated with precipitation that reached the ground. To the left of the weak echo region, six charge regions were inferred, with positive charge carried on hail at the bottom of the stack. Farther forward in the storm’s precipitation region, four charge regions were inferred, with negative charge at the bottom of the stack. There were different charge structures in adjacent regions of the storm at the same time, and regions of opposite polarity charge were horizontally adjacent at the same altitude. Flashes occasionally lowered positive charge to ground from the forward charge region. A conceptual model is presented that ties charge structure in different regions of the storm to storm structure inferred from radar reflectivity.

Radar and Lightning Observations of Normal and Inverted Polarity Multicellular Storms from STEPS

2007 ◽  
Vol 135 (11) ◽  
pp. 3682-3706 ◽  
Author(s):  
Sarah A. Tessendorf ◽  
Steven A. Rutledge ◽  
Kyle C. Wiens
Keyword(s):  
Los Alamos ◽  
Severe Thunderstorm ◽  
Charge Structure ◽  
Array Data ◽  
Lightning Detection ◽  
Normal Polarity ◽  
Mapping Array ◽  
Intracloud Discharges ◽  
Cg Lightning

Abstract This study discusses radar and lightning observations of two multicellular storms observed during the Severe Thunderstorm Electrification and Precipitation Study. The Lightning Mapping Array data indicated that the charge structure of the 19 June 2000 storm was consistent with a normal polarity tripole, while the 22 June 2000 storm exhibited an overall inverted tripolar charge structure. The 19 June storm consisted of weaker convection and produced little to no hail and moderate total flash rates peaking between 80 and 120 min−1. The cells in the 22 June 2000 storm were much more vigorous, exhibited strong, broad updrafts, and produced large quantities of hail, as well as extraordinary total flash rates as high as 500 min−1. The National Lightning Detection Network (NLDN) indicated that the 19 June storm produced mostly negative cloud-to-ground (CG) lightning, while the 22 June storm produced predominantly positive CG lightning, peaking at 10 min−1 just after two cells merged. However, the Los Alamos Sferic Array indicated that many of the positive CG strokes reported by the NLDN in the 22 June storm were intracloud discharges known as narrow bipolar events. Negative CG lightning was also observed in the 22 June storm, but typically came to ground beneath an inverted dipole in the storm anvil.

Radar and Lightning Observations of the 3 June 2000 Electrically Inverted Storm from STEPS

2007 ◽  
Vol 135 (11) ◽  
pp. 3665-3681 ◽  
Author(s):  
Sarah A. Tessendorf ◽  
Kyle C. Wiens ◽  
Steven A. Rutledge
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Convective Storm ◽  
Severe Thunderstorm ◽  
Mapping Array ◽  
Total Lack ◽  
Upper Level ◽  
Electrical Bias ◽  
Low Precipitation ◽  
Cg Lightning

Abstract This study addresses the kinematic, microphysical, and electrical evolution of an isolated convective storm observed on 3 June 2000 during the Severe Thunderstorm Electrification and Precipitation Study field campaign. Doppler-derived vertical velocities, radar reflectivity, hydrometeor classifications from polarimetric radar, and Lightning Mapping Array (LMA) charge structures are examined over a nearly 3-h period. This storm, characterized as a low-precipitation supercell, produced modest amounts of hail, determined by fuzzy-logic hydrometeor classification as mostly small (<2 cm) hail, with one surface report of large (≥2 cm) hail. Doppler-derived updraft speeds peaked between 20 and 25 m s−1, and reflectivity was never greater than 60 dBZ. The most striking feature of this storm was its total lack of cloud-to-ground (CG) lightning. Though this storm was electrically active, with maximum flash rates near 30 per minute, no CG flashes of either polarity were detected. The charge structure inferred from the LMA observations was consistent with an inverted dipole, defined as having a midlevel positive charge region below upper-level negative charge. Inverted charge structures have typically been considered conducive to producing positive CG lightning; however, the 3 June storm appeared to lack the lower negative charge layer below the inverted dipole that is thought to provide the downward electrical bias necessary for positive CG lightning.

scholarly journals Evolving Complex Electrical Structures of the STEPS 25 June 2000 Multicell Storm

2008 ◽  
Vol 136 (2) ◽  
pp. 741-756 ◽  
Author(s):  
Stephanie A. Weiss ◽  
W. David Rust ◽  
Donald R. MacGorman ◽  
Eric C. Bruning ◽  
Paul R. Krehbiel
Keyword(s):  
Great Plains ◽  
Negative Charge ◽  
Positive Charge ◽  
Three Dimensional ◽  
Lightning Flash ◽  
Severe Thunderstorm ◽  
Electrical Structure ◽  
High Reflectivity ◽  
Maximum Value ◽  
Mapping Array

Abstract Data from a three-dimensional lightning mapping array (LMA) and from two soundings by balloon-borne electric field meters (EFMs) were used to analyze the electrical structures of a multicell storm observed on 25 June 2000 during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). This storm had a complex, multicell structure with four sections, each of whose electrical structure differed from that of the others during all or part of the analyzed period. The number of vertically stacked charge regions in any given section of the storm ranged from two to six. The most complex charge and lightning structures occurred in regions with the highest reflectivity values and the deepest reflectivity cores. Intracloud flashes tended to concentrate in areas with large radar reflectivity values, though some propagated across more than one core of high reflectivity or into the low-reflectivity anvil. Intracloud lightning flash rates decreased as the vertical extent and maximum value of reflectivity cores decreased. Cloud-to-ground flash rates increased as cores of high reflectivity descended to low altitudes. Most cloud-to-ground flashes were positive. All observed positive ground flashes initiated between the lowest-altitude negative charge region and a positive charge region just above it. The storm’s complexity makes it hard to classify the vertical polarity of its overall charge structure, but most of the storm had a different vertical polarity than what is typically observed outside the Great Plains. The electrical structure can vary considerably from storm to storm, or even within the same storm, as in the present case.

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