Evolution of an Upward Negative Lightning Flash Triggered by a Distant +CG From a 257‐m‐Tall Tower, Including Initiation of Subsequent Strokes

Zhu, Yanan; Ding, Ziqin; Rakov, Vladimir A.; Tran, M. D.

doi:10.1029/2019gl083274

Cited by 12 publications

(7 citation statements)

References 32 publications

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“…Note that the E field records in Figure 7 are longer than the camera exposure time (rounded off to 50 μs), to take into account the uncertainty in alignment of the field and optical records. The method used to determine this uncertainty is described in detail by Zhu et al (2019). Specifically, for lower altitudes AGL (corresponding to Frames 168–170 in Figure 5), we found seven to eight “classical” leader step pulses (subjectively selected and marked by vertical arrows in Figure 7b) separated by 10 to 15 μs and smaller pulses in between separated by 2 μs or less.…”

Section: Data Presentation and Resultsmentioning

confidence: 99%

On a Possible Mechanism of Reactivation of Decayed Branches of Negative Stepped Leaders

et al. 2020

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Using visible-range and infrared (3-5 μm) high-speed video cameras, we observed luminosity transients that reilluminated decayed branches of two close (2 to 4 km) negative stepped leaders in Florida. Leader branches were energized via stepping at their tips and, as a result, were most heated near their lower ends, with the hotter sections being connected via cooler sections to the trunk. In the modeling of lightning leaders, usually a single tip is considered. In contrast, in the present study, many (up to 30 per major branch) tips were active at the same time, forming a network-like structure with a descending multitip "ionization front" whose transverse dimensions were of the order of hundreds of meters. The front exhibited alternating stepping, with each step necessarily generating a positive charge wave traveling from the leader tip up along the channel, like a mini return stroke. We inferred that the step-related waves can cause luminosity transients in the remnants of decayed negative branches at higher altitudes. Such reactivated branches, in turn, may facilitate further leader stepping at lower altitudes, as first reported by Stolzenburg et al. (2015, https://doi.org/10.1002/2014JD022933). The reactivation process is likely to involve multiple steps, as evidenced by a large number of active tips (some tens per 50-μs frame) and corresponding electric field pulses occurring at time intervals of 2 μs or less. Additionally, our observations suggest that a transient in one decayed branch can trigger (or assist with triggering of) a transient in another branch.

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Section: Data Presentation and Resultsmentioning

confidence: 99%

On a Possible Mechanism of Reactivation of Decayed Branches of Negative Stepped Leaders

et al. 2020

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“…A positive RS was often followed by a longer continue current, which lasts tens to hundreds of milliseconds, and is 1 order of magnitude larger than a negative CG lightning (Rakov, 2003). Furthermore, the transient E field changes resulting from the large charge moment of +CGs often induce transient luminous events (e.g., red sprites and halos) above the thundercloud (Boccippio et al, 1995;Lu et al, 2013;Lyons et al, 2003;van der Velde et al, 2014;Williams et al, 2010;Yang et al, 2008) and upward lightning from high structures on the ground (Saba et al, 2016;Schumann et al, 2019;Warner et al, 2012Warner et al, , 2013Wu et al, 2019;Yuan et al, 2017;Zhou et al, 2012;Zhu et al, 2019). A better understanding of the detailed discharge process of +CG flash will help to explain lightning mechanisms and its effects.…”

Section: Introductionmentioning

confidence: 99%

Origin of an Uncommon Multiple‐Stroke Positive Cloud‐to‐Ground Lightning Flash With Different Terminations

et al. 2020

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An uncommon three‐stroke positive cloud‐to‐ground (+CG) lightning flash was observed by synchronous multifrequency radiation sensors, and the three‐dimensional development of the channel was carefully mapped. Results show that three positive strokes grounded at different points approximately 4–8 km apart and time intervals between neighboring +CG strokes were 85 and 222 ms, respectively. This +CG flash was preceded by an intracloud (IC) discharge. The locations of the termination points on the ground were just below the preestablished horizontal IC discharge channels, and the three strokes were linked with each other through sharing horizontal negative leader channels inside the cloud. There were stepping pulses less than 0.4 ms before the first and second return strokes (RSs), and their location results were distributed nearby the following RS, indicating that the pulses might be associated with the attachment process. The first and second positive strokes occurred when the horizontal in‐cloud negative channel stopped extending, while the third positive stroke occurred below the opposite end of an advancing negative leader in the cloud. The above results suggest that the downward positive leader preceding the strokes possibly developed either from different decayed leader channels or from the opposite end of an advancing leader channel. A high‐speed camera captured a downward positive attempted leader from another +CG flash, revealing how a downward positive leader incepted from a horizontal negative lightning channel.

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“…It has been clear that upward flashes can occur with or without preceding lightning discharges, called “other‐triggered” and “self‐initiated” upward flashes, respectively (e.g., Wang et al, 2008). Numerous studies have been contributed to the triggering mechanism of upward negative flashes (Guimarães et al, 2014; Jiang et al, 2014; Pineda et al, 2019; Qi et al, 2018; Saba et al, 2016; Sunjerga et al, 2020; Takagi et al, 2006; Wang et al, 2008; Wang & Takagi, 2012a; Warner, 2012; Warner et al, 2012; Warner et al, 2014; Wu, Lyu, et al, 2019; Yuan et al, 2017; Zhou et al, 2012b; Zhu et al, 2019). One interesting phenomenon is that the ratio between other‐triggered and self‐initiated upward negative flashes varies significantly in different studies (e.g., Saba et al, 2016; Warner et al, 2012; Warner et al, 2014; Zhou et al, 2012b).…”

Section: Introductionmentioning

confidence: 99%

Upward Negative Leaders in Positive Upward Lightning in Winter: Propagation Velocities, Electric Field Change Waveforms, and Triggering Mechanism

Wang

Takagi

2020

JGR Atmospheres

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Upward negative leaders (UNLs) in positive upward lightning are rarely observed. In this study, 24 UNLs observed by the Fast Antenna Lightning Mapping Array during winter thunderstorms in Japan are analyzed. Three‐dimensional velocities of UNLs are calculated, and it is found that velocities during the upward propagation stage range from 1.8 to 27.9 × 105 m/s with a mean value of 10.4 × 105 m/s, and they are always larger than velocities during the following horizontal propagation stage. UNLs produce distinctive electric field change waveforms with V‐shaped overall change trend, with small pulses at the beginning when UNLs start, large pulses during upward propagations, and small pulses again when UNLs turn into horizontal directions. Pulses produced by UNLs are mainly unipolar but sometimes also bipolar. Pulse interval, pulse width, rise time, and fall time are calculated for waveforms produced by five UNLs. Pulse intervals range from 13.7 to 18.9 μs. Pulse width, rise time, and fall time are on average 5.8, 3.3, and 2.4 μs, respectively. All UNLs are preceded by other discharges. Strong negative strokes including some special types of strokes usually precede initiations of UNLs by tens of milliseconds. These negative strokes are usually found only a few kilometers away from UNLs. It is speculated that these negative strokes along with following in‐cloud positive leaders contribute to the depletion of negative charges in thunderclouds, which result in positive electric field changes (atmospheric electricity sign convention) large enough for initiations of UNLs.

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Evolution of an Upward Negative Lightning Flash Triggered by a Distant +CG From a 257‐m‐Tall Tower, Including Initiation of Subsequent Strokes

Cited by 12 publications

References 32 publications

On a Possible Mechanism of Reactivation of Decayed Branches of Negative Stepped Leaders

On a Possible Mechanism of Reactivation of Decayed Branches of Negative Stepped Leaders

Origin of an Uncommon Multiple‐Stroke Positive Cloud‐to‐Ground Lightning Flash With Different Terminations

Upward Negative Leaders in Positive Upward Lightning in Winter: Propagation Velocities, Electric Field Change Waveforms, and Triggering Mechanism

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