Electrical discharges in the overshooting tops of thunderstorms

MacGorman, Donald R.; Elliott, M.; DiGangi, Elizabeth

doi:10.1002/2016jd025933

Cited by 32 publications

(42 citation statements)

References 99 publications

(221 reference statements)

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“…While the bulk of the lightning occurred below 12 km altitude, the storm also featured significant VHF source activity above 15 km, within the OT (Figure 7a). OT‐based electrical activity has been noted before in the LMA literature (e.g., MacGorman et al, 2017), and similar to those studies, the activity tended to consist of continual low rates of sources without well‐defined channels. This may be related to the size of the physical discharges being small relative to the expected spatial resolution of the LMA at ranges like these (~1 km; Thomas et al, 2004).…”

Section: Case Study Analysis: 11 December 2018supporting

confidence: 76%

Distinctive Signals in 1‐min Observations of Overshooting Tops and Lightning Activity in a Severe Supercell Thunderstorm

et al. 2020

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This work examines a severe weather event that took place over central Argentina on 11 December 2018. The evolution of the storm from its initiation, rapid organization into a supercell, and eventual decay was analyzed with high-temporal resolution observations. This work provides insight into the spatio-temporal co-evolution of storm kinematics (updraft area and lifespan), cloud-top cooling rates, and lightning production that led to severe weather. The analyzed storm presented two convective periods with associated severe weather. An overall decrease in cloud-top local minima IR brightness temperature (MinIR) and lightning jump (LJ) preceded both periods. LJs provided the highest lead time to the occurrence of severe weather, with the ground-based lightning networks providing the maximum warning time of around 30 min. Lightning flash counts from the Geostationary Lightning Mapper (GLM) were underestimated when compared to detections from ground-based lightning networks. Among the possible reasons for GLM's lower detection efficiency were an optically dense medium located above lightning sources and the occurrence of flashes smaller than GLM's footprint. The minimum MinIR provided the shorter warning time to severe weather occurrence. However, the secondary minima in MinIR that preceded the absolute minima improved this warning time by more than 10 min. Trends in MinIR for time scales shorter than 6 min revealed shorter cycles of fast cooling and warming, which provided information about the lifecycle of updrafts within the storm. The advantages of using observations with high-temporal resolution to analyze the evolution and intensity of convective storms are discussed. Plain Language Summary Severe thunderstorms can have distinctive signals in satellite observations. Cloud-top temperature minima are one of the most studied metrics as a severe weather indicator. The newest geostationary weather satellites (GOES-16/17) offer a unique opportunity to study storms through their rapid-scan mode and lightning detector. In this study, we analyzed high-temporal (1-min) observations of cloud-top temperature and lightning detected from space and the surface to study the evolution of a severe thunderstorm that took place over central Argentina on 11 December 2018. Overall, cloud-top temperature minimum and fast increases in lightning activity preceded the occurrence of severe weather. The signature present in lightning observations provided the highest severe weather lead time, with ground-based sensors providing the maximum warning time (~30 min). A cloud-top temperature absolute minimum provided the shortest warning time, whereas secondary minima, that preceded the absolute minima, improved the warning time by more than 10 min. This improvement in lead time can result in better societal preparedness for imminent hazardous weather where no ground-based lightning observations are available. Observations with high-temporal resolution also show cycles of fast cloud-top cooling and warming that can provide important insight o...

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Section: Case Study Analysis: 11 December 2018supporting

confidence: 76%

Distinctive Signals in 1‐min Observations of Overshooting Tops and Lightning Activity in a Severe Supercell Thunderstorm

et al. 2020

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“…However, accounting for such lags may reduce the error associated with flash rate parameterizations. Finally, this study did not explicitly consider over-shooting top (OT) electrical discharges [89] or downward positive intracloud lightning (+IC) [90], which both occur at high altitudes and temperatures colder than the mixed-phase zone microphysical and kinematic parameters emphasized in this study. OT electrical discharges would be eliminated by the source-to-flash clustering methods used in this study and not included in our flash rate totals.…”

Section: Statistical Errorsmentioning

confidence: 99%

An Evaluation of Relationships between Radar-Inferred Kinematic and Microphysical Parameters and Lightning Flash Rates in Alabama Storms

Carey

Schultz

et al. 2019

Atmosphere

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Lightning flash rate parameterizations based on polarimetric and multi-Doppler radar inferred microphysical (e.g., graupel volume, graupel mass, 35 dBZ volume) and kinematic (e.g., updraft volume, maximum updraft velocity) parameters have important applications in atmospheric science. Although past studies have established relations between flash rate and storm parameters, their expected performance in a variety of storm and flash rate conditions is uncertain due to sample limitations. Radar network and lightning mapping array observations over Alabama of a large and diverse sample of 33 storms are input to hydrometeor identification, vertical velocity retrieval and flash rate algorithms to develop and test flash rate relations. When applied to this sample, prior flash rate linear relations result in larger errors overall, including often much larger bias (both over- and under-estimation) and root mean square errors compared to the new linear relations. At low flash rates, the new flash rate relations based on kinematic parameters have larger errors compared to those based on microphysical ones. Sensitivity of error to the functional form (e.g., zero or non-zero intercept) is also tested. When considering all factors (e.g., low errors including at low flash rate, consistency with past linear relations, and insensitivity to functional form), the flash rate parameterization based on graupel volume has the best overall performance.

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“…Journal of Geophysical Research: Atmospheres, 124, 6982-6998. https://doi.org/ 10. 1029/2018JD029907 et al, 2012 and discharges in the overshooting tops (e.g., MacGorman et al, 2017), we can find few reports of full-fledged IC flashes initiated at high altitudes such as above 12 km.…”

Section: 1029/2018jd029907mentioning

confidence: 83%

“…Calhoun et al () reported that the majority of lightning flashes in a supercell were initiated near altitudes of 10 to 11 km and noted that such supercell was “unusual” compared to other storms. In fact, other than some special types of lightning discharges that do not comprise clear leader channels, such as narrow bipolar events (NBEs; e.g., Smith et al, ; Wu et al, ) and discharges in the overshooting tops (e.g., MacGorman et al, ), we can find few reports of full‐fledged IC flashes initiated at high altitudes such as above 12 km.…”

Section: Introductionmentioning

confidence: 99%

Intracloud Lightning Flashes Initiated at High Altitudes and Dominated by Downward Positive Leaders

Wang

Takagi

2019

JGR Atmospheres

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Intracloud (IC) lightning flashes are normally initiated below 10 km and start with upward negative leaders. In this paper, we report a special type of IC flash called “downward positive IC (+IC) flash” which is initiated at high altitudes (mainly above 12 km) and whose initial negative leaders do not propagate upward. Three‐dimensional location results of three downward +IC flashes are described in detail. It is demonstrated that downward +IC flashes start with positive leaders propagating downward with speeds on the order of 104 m/s and negative leaders propagating horizontally for only a short distance. Downward +IC flashes are produced in thunderstorms with deep convective updrafts (radar echoes of cloud tops typically higher than 14 km). The charge structure responsible for downward +IC flashes is inferred to be a positive dipole including a negative charge region at a normal altitude (near the −10 °C isotherm) and an upper positive charge region at a relatively high altitude (usually above the −50 °C isotherm), with downward +IC flashes likely initiated from the upper positive charge region. Further, lightning flashes in a thunderstorm producing a large number of downward +IC flashes are analyzed. Results show that normal IC flashes in this thunderstorm are also initiated at altitudes closer to the upper positive charge region and usually consist of downward positive leaders propagating for longer distances than upward negative leaders. Based on these results, we propose a relationship between the altitude of the upper positive charge region and initiation locations of IC flashes.

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Electrical discharges in the overshooting tops of thunderstorms

Cited by 32 publications

References 99 publications

Distinctive Signals in 1‐min Observations of Overshooting Tops and Lightning Activity in a Severe Supercell Thunderstorm

Distinctive Signals in 1‐min Observations of Overshooting Tops and Lightning Activity in a Severe Supercell Thunderstorm

An Evaluation of Relationships between Radar-Inferred Kinematic and Microphysical Parameters and Lightning Flash Rates in Alabama Storms

Intracloud Lightning Flashes Initiated at High Altitudes and Dominated by Downward Positive Leaders

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