Lightning Channels of Cloud-to-Ground Flashes Neutralizing Multiple Charge Regions Inside Winter Thunderclouds

Akita, Manabu; Yoshida, Shigeaki; Nakamura, Yoshitaka; Morimoto, Takeshi; Ushio, Tomoo; Kawasaki, Zen‐Ichiro; Wang, Daohong

doi:10.1541/ieejfms.130.467

Cited by 2 publications

(6 citation statements)

References 17 publications

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“…The charge regions of the flash can be identified by examining the negative recoil leaders (recoil leaders) seen prominently in Figure a as vertical clusters of sources. These recoil leaders travel from the negative charge region toward and sometimes into the positive charge region [ Shao and Krehbiel , ; Akita et al ., ]. Such a leader is shown in Figure b colored by time for the duration of the recoil leader.…”

Section: Resultsmentioning

confidence: 99%

“…Once the lightning channels in the negative charge region are of sufficient length, numerous recoil leaders are seen traveling from the negative charge region toward the origin of the flash. Previous studies give recoil leader velocities on the order of 10 6 –10 7 m/s [e.g., Shao and Krehbiel , ; Akita et al ., ]. The upgraded digitizer greatly improves the source mappings for recoil events.…”

Section: Resultsmentioning

confidence: 99%

“…The VHF broadband interferometer (VHF DITF) developed by the Lightning Research Group of Osaka University extended broadband interferometry technique to two spatial dimensions (azimuth and elevation) using three antennas forming two perpendicular baselines [ Ushio et al ., ; Morimoto et al ., ]. The VHF DITF has been used to contribute to the understanding of complicated radiation processes such as chaotic leaders just before return strokes and the initial continuing current of upward lightning, as well as other topics [ Gomes et al ., ; Yoshida et al ., ; Akita et al ., ; Yoshida et al ., ].The VHF DITF initially used a sequential triggering technique in which limited digitizer memory was divided into a few thousand 2 µs records, allowing the VHF DITF to locate up to 2048 radiation sources during a lightning flash [ Mardiana and Kawasaki , ; Morimoto et al ., ]. In this study, the digitizing memory has been greatly expanded allowing for continuous sampling of the VHF radiation from lightning for 2 s or longer.…”

Section: Introductionmentioning

confidence: 98%

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Data processing procedure using distribution of slopes of phase differences for broadband VHF interferometer

et al. 2014

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The upgraded VHF digital interferometer (VHF DITF) system is introduced which can continuously sample the radiation associated with lightning. A new processing technique was implemented which uses the distribution of slopes of the phase difference versus frequency to locate the radiation source. By using this technique, frequency components which are not due to lightning can be excluded and low as well as high amplitude sources are located. As a result, both positive breakdown and negative breakdown are located, and negative recoil leaders (recoil leaders) are visualized in great detail. The recoil leaders which continue into the positive charge region are seen to slow their propagation and dim their radiation as they cross the flash initiation region. Analysis of the relative received power of the different breakdown types, negative leaders, recoil leaders, and positive leaders, also can be made. In both the intracloud and cloud-to-ground flash, the modes of the distributions of received power for negative leaders, recoil leaders, and positive leaders were approximately the same. The brightest emissions seen from the positive leader were substantially lower than the brightest emission seen from the negative leader. The results also indicate that positive leaders as well as lower elevation negative leader emit more low frequency radiation than recoil leaders and high-elevation negative leaders. By continuously sampling the VHF waveform, the upgraded VHF DITF locates many weak sources which the previous system was not capable of locating.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Data processing procedure using distribution of slopes of phase differences for broadband VHF interferometer

et al. 2014

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“…In particular, our observation system compared with a narrowband TOA system has the advantage of detecting fast-propagating processes, such as recoil streamers associated with K changes (e.g., Kitagawa 1957;Ogawa and Brook 1964;Akita et al 2010a), by higher coherency with high temporal resolution in 2D mapping. The system is well suited for continuous remote observation in winter-in the arrival time differences of three pulses using the cross-correlation method.…”

Section: Summary and Future Workmentioning

confidence: 99%

“…Observation of VHF pulses can visualize lightning channels in three dimensions (3D). There are, however, few reports concerning winter lightning mapping in 3D (Morimoto et al 2004;Akita et al 2010b), and no meteorological lightning research using 3D winter lightning mapping and meteorological radar data. Previously, interferometry was utilized primarily for narrowband and two-dimensional (2D) lightning mapping (Hayenga and Warwick 1981;Rhodes et al 1994;Shao et al 1995), but recently it has been developed for broadband mapping (Shao et al 1996;Ushio et al 1997;Mardiana and Kawasaki 2000;Morimoto et al 2004;Tantisattayakul et al 2005;Qiu et al 2009) and used to conduct 3D lightning mapping (Mardiana et al 2002;Morimoto et al 2004Morimoto et al , 2005Tantisattayakul et al 2005;Akita et al 2010aAkita et al , 2011.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional VHF Lightning Mapping System for Winter Thunderstorms

Nishihashi¹,

Shimose²,

Kusunoki

et al. 2013

Journal of Atmospheric and Oceanic Technology

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A three-dimensional (3D) winter lightning mapping system employing very high frequency (VHF) broadband signals was developed for continuous remote observation in winter. VHF broadband pulses radiated by leader progression are received with three discone antennas arranged in a triangle (20-30 m) and recorded on a high-speed digital oscilloscope (1.25-GHz sampling) with GPS digital timing data. The two-dimensional (2D) mapping for azimuth and elevation of the VHF radiation sources was conducted by computing the arrival time differences of three pulses using a cross-correlation technique. From azimuth and elevation data from two sites extracted within a given time frame, 3D lightning mapping was performed using the triangulation scheme. An observation network for winter lightning was constructed within a comprehensive meteorological observation network in the Shonai area, which is located on the coast of the Japan Sea. This report includes the preliminary 2D and 3D mapping of winter lightning observed on 3 December 2010. The horizontal and vertical distributions of VHF radiation sources were consistent with the radar echo observed with X-band Doppler radar. These results indicate that the system can detect winter lightning discharges and perform 2D and 3D lightning mapping in detail.

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Lightning Channels of Cloud-to-Ground Flashes Neutralizing Multiple Charge Regions Inside Winter Thunderclouds

Cited by 2 publications

References 17 publications

Data processing procedure using distribution of slopes of phase differences for broadband VHF interferometer

Data processing procedure using distribution of slopes of phase differences for broadband VHF interferometer

Three-Dimensional VHF Lightning Mapping System for Winter Thunderstorms

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