The U.S. National Lightning Detection Network TM (NLDN) has provided lightning data covering the continental United States since 1989. Using information gathered from more than 100 sensors, the NLDN provides both real-time and historical lightning data to the electric utility industry, the National Weather Service, and other government and commercial users. It is also the primary source of lightning data for use in research and climatological studies in the United States. In this paper we discuss the design, implementation, and data from the time-of-arrival/magnetic direction finder (TOA/MDF) network following a recent system-wide upgrade. The location accuracy (the maximum dimension of a confidence region around the stroke location) has been improved by a factor of 4 to 8 since 1991, resulting in a median accuracy of 500 m. The expected flash detection efficiency ranges from 80% to 90% for those events with peak currents above 5 kA, varying slightly by region. Subsequent strokes and strokes with peak currents less than 5 kA can now be detected and located; however, the detection efficiency for these events is not quantified in this study because their peak current distribution is not well known.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98JD00153

A Combined TOA/MDF Technology Upgrade of the U.S. National Lightning Detection Network

Lightning in all corners of the world is monitored by one or more land- or space-based lightning locating systems (LLSs). The applications that have driven these developments are numerous and varied. This paper describes the history leading to modern LLSs that sense lightning radiation fields at multiple remote sensors, focusing on the interactions between enabling technology, scientific discovery, technical development, and uses of the data. An overview of all widely used detection and location methods is provided, including a general discussion of their relative strengths and weaknesses for various applications. The U.S. National Lightning Detection Network (NLDN) is presented as a case study, since this LLS has been providing real-time lightning information since the early 1980s, and has provided continental-scale (U.S.) information to research and operational users since 1989. This network has also undergone a series of improvements during its >20-year life in response to evolving detection technologies and expanding requirements for applications. Recent analyses of modeled and actual performance of the current NLDN are also summarized. The paper concludes with a view of the short- and long-term requirements for improved lightning measurements that are needed to address some open scientific questions and fill the needs of emerging applications.

An Overview of Lightning Locating Systems: History, Techniques, and Data Uses, With an In-Depth Look at the U.S. NLDN

The influence of vertical wind shear on the azimuthal distribution of cloud-to-ground lightning in tropical cyclones was examined using flash locations from the National Lightning Detection Network. The study covers 35 Atlantic basin tropical cyclones from 1985–99 while they were over land and within 400 km of the coast over water. A strong correlation was found between the azimuthal distribution of flashes and the direction of the vertical wind shear in the environment. When the magnitude of the vertical shear exceeded 5 m s−1, more than 90% of flashes occurred downshear in both the storm core (defined as the inner 100 km) and the outer band region (r = 100–300 km). A slight preference for downshear left occurred in the storm core, and a strong preference for downshear right in the outer rainbands. The results were valid both over land and water, and for depression, storm, and hurricane stages. It is argued that in convectively active tropical cyclones, deep divergent circulations oppose the ver...

/pdf/the-effects-of-vertical-wind-shear-on-the-distribution-of-2nvw9vdswu.pdf

The Effects of Vertical Wind Shear on the Distribution of Convection in Tropical Cyclones

http://wwlln.net/publications/dowden.toga.article.pdf

VLF lightning location by time of group arrival (TOGA) at multiple sites

DUNDEE (Down Under Doppler and Electricity Experiment) is described. DUNDEE was carded out in the vicinity of Darwin, Northern Territory, Australia, during the wet seasons of November 1988 through February 1989, and November 1989 through February 1990. The general goal of DUNDEE was to investigate the dynamical and electrical properties of tropical mesoscale convective systems and isolated deep convective storms. Darwin, situated at the southern tip of the “maritime continent,” experiences both monsoon and “break” period conditions during the wet season. We discuss the observational network deployed for DUNDEE and present preliminary scientific results. One particularly interesting observation is a large contrast in the frequency of total lightning between break period convection (high lightning rates) and convection in the monsoon trough (low lightning rates). A relationship between CAPE (convective available potentional energy) and total flash rate is presented and discussed to explain this obs...

The Down Under Doppler and Electricity Experiment (DUNDEE): Overview and Preliminary Results

A magnetic direction finder has been developed which utilizes only the initial few microseconds of wideband return stroke waveforms to provide accurate directions to the channel bases of lightning discharges to ground. Bearing errors are minimized because, near the ground, most channels tend to be straight and vertical with no large branches or horizontal sections. Tests on a number of lightning storms at distances of 10 to 100 km indicate the angular resolution is in the range 1-2 deg, with little or no systematic dependence on azimuth or distance.

A Gated, Wideband Magnetic Direction Finder for Lightning Return Strokes

Broadband magnetic antenna systems suitable for recording submicrosecond field changes are described, and typical data from distant lightning are presented Two types of systems are described, one with a high-impedance antenna loop connected to the integrator by a twisted pair of coaxial cables and another with the antenna loop and twisted signal loops formed from a single piece of coaxial cable Data for correlated magnetic and electric field waveforms from lightning at a distance of 50 to 100 km are presented and are shown to be almost identical

/pdf/broadband-antenna-systems-for-lightning-magnetic-fields-lamw1v97z1.pdf

Broadband antenna systems for lightning magnetic fields

A lightning detection system utilizes a gated magnetic direction finder for determining the range and direction of lightning discharges to ground. The magnetic direction finder is controlled by an electric field detector that includes logic circuitry for analyzing the waveforms of the detected electric field to determine whether the discharge is a ground stroke or other type of discharge, or background noise. The magnetic direction finder is gated by the electric field control logic circuitry so that a direction measurement may be made for a few microseconds after it has been determined from the electric field waveform analysis that a ground stroke has occurred. Different criteria are used for determining whether or not a stroke is a ground stroke depending on whether the stroke being analyzed is the first stroke in a flash or a subsequent stroke.

Gated lightning detection system

A lightning detection system utilizes a gated magnetic direction finder for determining the range and direction of lightning discharges to ground. Logic circuitry is provided for controlling gating circuits within the direction finder so that the direction measurement is made during the initial few microseconds of the return stroke waveform, thereby minimizing errors caused by nonvertical lightning channels to ground, branches and intracloud discharges. Distance measurements are made by analyzing the amplitude of the detected return stroke waveform, or by utilizing two or more geographically separated direction finders and triangulation techniques. The waveforms of the signals received by the direction finder are analyzed to determine whether the discharge is ground stroke or another type of discharge, or background noise. Further circuitry can be used to distinguish between various types of ground strokes, such as first strokes or subsequent strokes in a flash.

Detection system for lightning

Survey spectra of the Apollo 17/Saturn V exhaust plume during launch were obtained in the ultraviolet, visible, and near infrared. The plume resembles a blackbody source for about 40 m from the exit plane, and beyond this point the characteristic radiation is the sodium D-lines. The spectral data support previous reports mat the peak exhaust temperature is near 2600 K, which in turn suggests the conductivity in the upper 40 m of plume is in the range 10 7 to 10 4 mho/cm or higher. We examine the implication of these results for the initiation of lightning such as occurred during the launch of Apollo 12.

R. C. Noggle

Papers

A Gated, Wideband Magnetic Direction Finder for Lightning Return Strokes

Broadband antenna systems for lightning magnetic fields

Gated lightning detection system

Detection system for lightning

Lightning and the Apollo 17/Saturn V Exhaust Plume