Initial results of LF sensor network for lightning observation and characteristics of lightning emission in LF band

Abstract

We have been developing an LF sensor network called Broadband Observation network forLightning and Thunderstorm (BOLT), to image the structure of lightning discharges in 3D using time of arrival (TOA) technique. This paper documents initial results and characteristics of BOLT source locations for further understanding of LF radiation associated with lightning. Theoretical reduced Chi-square distribution fitted to BOLT observation data indicates a root mean square (rms) timing error of about 200 ns for each sensor. Monte Carlo simulations of BOLT indicate that at an altitude of 5000 m the standard deviations for horizontal differences between a known source and a location that the BOLT algorithm produces are less than 200 m, and vertical differences are less than 400 m in most of the network. Furthermore, comparison of BOLT and VHF source locations arriving at the same site within 5 μs indicates that the average difference for elevation direction is 0.73°with a standard deviation of 3.64°, and that for the azimuth direction is 0.58°with a standard deviation of 1.98°. Lightning flash processes of intracloud (IC) and cloud-to-ground (CG) flashes, including preliminary breakdown pulses, negative leaders, breakdown in the negative charge region (NCR), and an attempted leader, are well imaged by BOLT. Normalized amplitudes in E-field change waveform of BOLT sources associated with negative leaders and breakdown occurred in the NCR do not have significant difference, implying that most BOLT sources in the NCR might be associated with negative recoil leaders.

Relationship between thunderstorm electrification and storm kinetics revealed by phased array weather radar

“…The LF sensor array in the current study is quite similar to that deployed by Yoshida et al . []. Monte Carlo simulations (not shown) for the estimation of BOLT location errors in the current study array indicate similar location errors to those reported by Yoshida et al .…”

“…[]. We update the locating algorithm described in Yoshida et al [], where we apply a band‐passed digital filter with a passband of 230–500 kHz before identifying the pulse peaks in the LF records, succeeding in producing much more BOLT source locations than those in the previous location algorithm. In this study, the BOLT source location is estimated based on seven or more stations.…”

Preliminary breakdown of intracloud lightning: Initiation altitude, propagation speed, pulse train characteristics, and step length estimation

“…Time‐of‐arrival technique was employed to obtain 3‐D locations of lightning discharges as described in Yoshida et al . [].…”

Electrical charge associated with cloud-to-ground lightning discharge in the Shonai area, Tohoku district, Japan

“…Radiation sources often show horizontal layered structures inside clouds related to intra-cloud (IC) and/or cloud-to-ground (CG) lightning discharges. Previous studies have demonstrated that these layers correspond to charge layers formed in clouds, and extended discussions of electrical characteristics based on that assumption have been published (Krehbiel et al, 1979;Williams, 1989: Bateman et al, 1999Shao and Krehbiel, 1996;Thomas et al, 2001;Coleman et al, 2003;Riousset et al, 2007;Yoshida et al, 2014). These results have demonstrated the usefulness of three-dimensional monitoring of lightning discharges using electromagnetic waves of VHF or other bands.…”