A Combined TOA/MDF Technology Upgrade of the U.S. National Lightning Detection Network
TL;DR: The U.S. National Lightning Detection Network (NLDN) has provided real-time and historical lightning data to the electric utility industry, the National Weather Service, and other government and commercial users.
Abstract: 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.
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TL;DR: 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 are described.
Abstract: 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.
586 citations
Cites background or methods from "A Combined TOA/MDF Technology Upgra..."
...However, location errors for DF systems are directly proportional to baseline distances , so a network composed of DF sensors with 200-300 km baselines can only provide location accuracy in the range of 2-4 km at best [53]....
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...Performance of the NLDN after the upgra de was modeled in [53], and validated in independent studies [106]-[107], [52]....
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...This resulted in t he re-deployment of ARSI’s LPATS III sensors in conjunction with new combined MDF:TOA (IMPACT) sensors during late 1994 and early 1995 [53]....
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TL;DR: The best estimate of the annual global LNOx nitrogen oxides nitrogen mass source and its uncertainty range is (5±3) Tg a−1 in this paper, implying larger flash-specific NOx emissions.
Abstract: . The knowledge of the lightning-induced nitrogen oxides (LNOx) source is important for understanding and predicting the nitrogen oxides and ozone distributions in the troposphere and their trends, the oxidising capacity of the atmosphere, and the lifetime of trace gases destroyed by reactions with OH. This knowledge is further required for the assessment of other important NOx sources, in particular from aviation emissions, the stratosphere, and from surface sources, and for understanding the possible feedback between climate changes and lightning. This paper reviews more than 3 decades of research. The review includes laboratory studies as well as surface, airborne and satellite-based observations of lightning and of NOx and related species in the atmosphere. Relevant data available from measurements in regions with strong LNOx influence are identified, including recent observations at midlatitudes and over tropical continents where most lightning occurs. Various methods to model LNOx at cloud scales or globally are described. Previous estimates are re-evaluated using the global annual mean flash frequency of 44±5 s−1 reported from OTD satellite data. From the review, mainly of airborne measurements near thunderstorms and cloud-resolving models, we conclude that a "typical" thunderstorm flash produces 15 (2–40)×1025 NO molecules per flash, equivalent to 250 mol NOx or 3.5 kg of N mass per flash with uncertainty factor from 0.13 to 2.7. Mainly as a result of global model studies for various LNOx parameterisations tested with related observations, the best estimate of the annual global LNOx nitrogen mass source and its uncertainty range is (5±3) Tg a−1 in this study. In spite of a smaller global flash rate, the best estimate is essentially the same as in some earlier reviews, implying larger flash-specific NOx emissions. The paper estimates the LNOx accuracy required for various applications and lays out strategies for improving estimates in the future. An accuracy of about 1 Tg a−1 or 20%, as necessary in particular for understanding tropical tropospheric chemistry, is still a challenging goal.
573 citations
Cites background or methods from "A Combined TOA/MDF Technology Upgra..."
...The systems use magnetic direction finders (Cummins et al., 1998), time of arrival (Shao and Krehbiel, 1996) or VHF interferometers techniques (Defer et al., 2001) to evaluate the location of the lightning sources....
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...These systems report mainly strong (>5 kA) CG strokes (Cummins et al., 1998)....
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TL;DR: In this paper, the location uncertainty of the New Mexico Tech Lightning Mapping Array (LMA) has been investigated experimentally using sounding balloon measurements, airplane tracks, and observations of distant storms.
Abstract: [1] The location accuracy of the New Mexico Tech Lightning Mapping Array (LMA) has been investigated experimentally using sounding balloon measurements, airplane tracks, and observations of distant storms. We have also developed simple geometric models for estimating the location uncertainty of sources both over and outside the network. The model results are found to be a good estimator of the observed errors and also agree with covariance estimates of the location uncertainties obtained from the least squares solution technique. Sources over the network are located with an uncertainty of 6–12 m rms in the horizontal and 20–30 m rms in the vertical. This corresponds well with the uncertainties of the arrival time measurements, determined from the distribution of chi-square values to be 40–50 ns rms. Outside the network the location uncertainties increase with distance. The geometric model shows that the range and altitude errors increase as the range squared, r2, while the azimuthal error increases linearly with r. For the 13 station, 70 km diameter network deployed during STEPS the range and height errors of distant sources were comparable to each other, while the azimuthal errors were much smaller. The difference in the range and azimuth errors causes distant storms to be elongated radially in plan views of the observations. The overall results are shown to agree well with hyperbolic formulations of time of arrival measurements [e.g., Proctor, 1971]. Two appendices describe (1) the basic operation of the LMA and the detailed manner in which its measurements are processed and (2) the effect of systematic errors on lightning observations. The latter provides an alternative explanation for the systematic height errors found by Boccippio et al. [2001] in distant storm data from the Lightning Detection and Ranging system at Kennedy Space Center.
385 citations
Cites methods from "A Combined TOA/MDF Technology Upgra..."
...[11] Data from the National Lightning Detection Network (NLDN) [Cummins et al., 1998] show that the flash was a multiple-stroke CG discharge that lowered negative charge to ground....
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TL;DR: 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 as discussed by the authors.
Abstract: 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...
377 citations
TL;DR: The second part of a two-part study examines the lightning and charge structure evolution of the 29 June 2000 tornadic supercell observed during the Severe Thunderstorm Electrification and Precipitation Study (STEPS) as discussed by the authors.
Abstract: This second part of a two-part study examines the lightning and charge structure evolution of the 29 June 2000 tornadic supercell observed during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). Data from the National Lightning Detection Network and the New Mexico Tech Lightning Mapping Array (LMA) are used to quantify the total and cloud-to-ground (CG) flash rates. Additionally, the LMA data are used to infer gross charge structure and to determine the origin locations and charge regions involved in the CG flashes. The total flash rate reached nearly 300 min−1 and was well correlated with radar-inferred updraft and graupel echo volumes. Intracloud flashes accounted for 95%–100% of the total lightning activity during any given minute. Nearly 90% of the CG flashes delivered a positive charge to ground (+CGs). The charge structure during the first 20 min of this storm consisted of a midlevel negative charge overlying lower positive charge with no evidence of an upper positiv...
348 citations
Cites background from "A Combined TOA/MDF Technology Upgra..."
...According to Cummins et al. (1998), CG flashes with peak currents less than 10 kA may in fact be intracloud flashes that the NLDN misidentifies as CG flashes....
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...The National Lightning Detection Network (NLDN; Cummins et al. 1998) provided measurements of the time, strike location, polarity, and peak current of CG flashes....
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References
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TL;DR: For the case of a finite linear antenna along which a fixed current waveform propagates, the authors presented analytical time−domain solutions for the electric and magnetic radiation (far) fields.
Abstract: Textbooks rarely give time−domain solutions to antenna problems. For the case of a finite linear antenna along which a fixed current waveform propagates, we present analytical time−domain solutions for the electric and magnetic radiation (far) fields. We also give computer solutions for the total (near and far) fields. The current waveform used as an example in the computer calculations approximates that of a lightning return−stroke, a common geophysical example of the type of radiation source under consideration.
486 citations
TL;DR: In this article, a magnetic direction finder was 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.
Abstract: 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.
228 citations
TL;DR: In this paper, it was shown that the reliability of a fix does not depend on the size of the particular "cocked hat" from which it is derived, and the reciprocal of the root-mean-square error expected in the position of the fix should be adopted as the conventional standard quantity for measuring the reliability.
Abstract: The paper deals with the location of an object of u nknown position, on which bearings are taken from two or more stations whose positions are known, and provides solutions to the two problems:-(a) Given a set of bearings, what is the most probable position of the object?(b) How far from the true position is the position indicated by the “fix” likely to be?Diagrams are given to show the results of applying the theory to typical practical cases.It is shown that, subject to certain qualifications, reliability of a fix does not depend on the size of the particular “cocked hat” from which it is derived.It is proposed that the reciprocal of the root-mean-square error expected in the position of the fix should be adopted as the conventional standard quantity for measuring the reliability of a fix.
217 citations