Global distribution and properties of continuing current in lightning

Bitzer, Phillip M.

doi:10.1002/2016jd025532

Cited by 54 publications

(114 citation statements)

References 46 publications

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“…We define these features as LIS “series,” and they are meant to describe distinct optical pulses that are separated by “dark” periods with no groups detected. These features result from physical lightning processes such as propagation (Peterson, Deierling, et al, ) or continuing current (Bitzer, ). A series feature is defined as any collection of groups within the same flash separated in time by no more than 1 LIS frame.…”

Section: Methodsmentioning

confidence: 99%

“…Lightning imagers map the evolution of optical energy produced by lightning in space and time at a nominal 500 frames per second. The primary motivations for examining the frame‐by‐frame evolution of individual flashes have been to validate independent lightning measurements (Rudlosky et al, ) and to identify important components of the flash such as the return stroke (Koshak, ) or continuing currents (Bitzer, ). Changes in the extent, position, and radiance of the optical signals are indicative of such physical lightning processes, but these signals are modified by scattering in the cloud medium (Peterson, Deierling, et al, ; Thomson & Krider, ).…”

Section: Introductionmentioning

confidence: 99%

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Mapping the Lateral Development of Lightning Flashes From Orbit

2018

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Optical lightning measurements from the Lightning Imaging Sensor (LIS) are used to map the lateral development of lightning flashes and produce statistics that describe their motion through the electrified cloud. This is accomplished by monitoring the frame‐by‐frame (group‐level) evolution of the optical signals produced during each flash. While the optical flash properties recorded by LIS gravitate towards the most exceptional optical signals produced during the flash, group‐level data describe the evolution and lateral development of the flash resulting from physical lightning process that emits enough light out of the top of the cloud to be detected from orbit. The groups that comprise LIS flashes constitute examples of complex lateral flash structure that can extend 80 km in length with dozens to hundreds of visible branches. The lateral development of individual flashes is described in terms of its speed and direction of motion, whether the development extends the overall length of the flash or reilluminates an existing segment, and whether it is directed inbound or outbound with respect to the origin. Sixty‐five percent of propagating groups are directed outbound from the origin, 22% extend the length of the flash, and 3–5% reilluminate an existing branch. LIS flashes are commonly oriented from east to west and develop at speeds ranging from 104 to 106 m/s, consistent with large‐scale leader development. These results provide evidence that lightning imagers may be used in conjunction with Lightning Mapping Array systems to document physical lightning phenomena across global domains.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mapping the Lateral Development of Lightning Flashes From Orbit

2018

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“…The 1–2% of series contain two bright groups at the 1‐sigma level, while fewer than 1% contain 3. Thus, when Bitzer () discusses continuing current with five or more sequential groups, these are very rarely sequences of groups with a sustained high radiance—if they contain a bright group in the first place.…”

Section: Resultsmentioning

confidence: 99%

“…We examine the sensitivity of our series features to the chosen empty frame threshold by constructing a data set of two million LIS flashes that considers the three most elementary definitions of quasi‐sequential groups. These definitions include no empty frames allowed between groups in the same series—which is identical to the time‐adjacent groups in Bitzer ()—and either 1 frame or 2 frames allowed between groups. Table compares the resulting statistics.…”

Section: Methodsmentioning

confidence: 99%

“…Koshak () and Koshak and Solakiewicz () subsequently developed algorithms to compute the fractions of CG and IC flashes—known as the Z‐ratio (Mackerras et al, ; Prentice & Mackerras, )—for a large sample of optical lightning flashes based on statistical differences in MGA between CG and IC flashes. Bitzer () additionally inferred continuing currents by detecting collections of sequential groups in the same flash.…”

Section: Introductionmentioning

confidence: 99%

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The Time Evolution of Optical Lightning Flashes

Peterson

Rudlosky

2019

JGR Atmospheres

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The composition and time evolution of lightning are examined using the Lighting Imaging Sensor (LIS). Frame‐by‐frame optical lightning measurements are clustered into features whose radiant energy, horizontal footprint, and timing may be analyzed statistically. A LIS series feature is used to describe distinct periods of near continuous illumination that persists over multiple LIS frames. Series are integrated into the LIS clustering hierarchy between the group and flash level. An average series illuminates 40% of the flash footprint while accounting for 20% of the flash radiance, and just 1% of the flash duration. LIS flashes typically contain optical emissions that are exceptionally radiant and may persist over multiple frames. Series features cluster these bright optical pulses, allowing their number and time separation to be quantified in each flash. This optical multiplicity averages 1.7 for flashes with at least one particularly radiant group. Multigroup series most often occur early in the flash duration with 13% to 18% at first light. Series are typically separated by 100 ms or more in multiseries flashes. Bright series, by contrast, typically occur in rapid succession, with at most a few dozen milliseconds between them. Because series are optical features, they may result from any physical process that produces strong optical emissions. The statistics presented herein support the idea that series may originate from multiple physical processes.

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The Evolution and Structure of Extreme Optical Lightning Flashes

2017

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This study documents the composition, morphology, and motion of extreme optical lightning flashes observed by the Lightning Imaging Sensor (LIS). The furthest separation of LIS events (groups) in any flash is 135 km (89 km), the flash with the largest footprint had an illuminated area of 10,604 km2, and the most dendritic flash has 234 visible branches. The longest‐duration convective LIS flash lasted 28 s and is overgrouped and not physical. The longest‐duration convective‐to‐stratiform propagating flash lasted 7.4 s, while the longest‐duration entirely stratiform flash lasted 4.3 s. The longest series of nearly consecutive groups in time lasted 242 ms. The most radiant recorded LIS group (i.e., “superbolt”) is 735 times more radiant than the average group. Factors that impact these optical measures of flash morphology and evolution are discussed. While it is apparent that LIS can record the horizontal development of the lightning channel in some cases, radiative transfer within the cloud limits the flash extent and level of detail measured from orbit. These analyses nonetheless suggest that lightning imagers such as LIS and Geostationary Lightning Mapper can complement ground‐based lightning locating systems for studying physical lightning phenomena across large geospatial domains.

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Global distribution and properties of continuing current in lightning

Cited by 54 publications

References 46 publications

Mapping the Lateral Development of Lightning Flashes From Orbit

Mapping the Lateral Development of Lightning Flashes From Orbit

The Time Evolution of Optical Lightning Flashes

The Evolution and Structure of Extreme Optical Lightning Flashes

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