Abstract. The U.S. National Lightning Detection Network TM (NLDN) has provided lightning data coveting 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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Ground-based and satellite-based lightning locating systems are the most common ways to detect and geolocate lightning. Depending upon the frequency range of operation, LLSs may report a variety of processes and characteristics associated with lightning flashes including channel formation, leader pulses, cloud-to-ground return strokes, M-components, ICC pulses, cloud lightning pulses, location, duration, peak current, peak radiated power and energy, and full spatial extent of channels. Lightning data from different types of LLSs often provide complementary information about thunderstorms. For all the applications of lightning data, it is critical to understand the information that is provided by various lightning locating systems in order to interpret it correctly and make the best use of it. In this study, we summarize the various methods to geolocate lightning, both ground-based and satellite-based, and discuss the characteristics of lightning data available from various sources. The performance characteristics of lightning locating systems are determined by their ability to geolocate lightning events accurately with high detection efficiency and with low false detections and report various features of lightning correctly. Different methods or a combination of methods may be used to validate the performance characteristics of different types of lightning locating systems. We examine these methods and their applicability in validating the performance characteristics of different LLS types.

We have analyzed the lightning activity recorded during the Stratosphere‐Troposphere Experiment: Radiation, Aerosols, and Ozone (STERAO‐A) July 10, 1996, storm by the Office National d'Etudes et de Recherches Aérospatiales (ONERA) lightning VHF interferometer and the National Lightning Detection Network (NLDN) system. Both cloud‐to‐ground and total lightning activity were observed and studied for the entire 5‐hour life of the storm. The July 10 storm was a multicellular complex, which became unicellular during the last hour. It primarily exhibited high intracloud activity with only 1.5% cloud‐to‐ground flashes. The maximum value of the total flash rate was 58 flashes per minute. Cloud‐to‐ground (CG) flashes occurred after some intracloud flashes with a delay ranging from 3 to 26 min for the different cells of the storm. Our study revealed that measured flash duration ranged from 23 μs to 1.8 s. Flash duration, averaged over 5‐min periods, increased during the storm life. Short‐duration flashes (<1 ms) did not occur until 30 min after the initial flash in the storm when the 50 dBZ vertical profile reached 8 km mean sea level (msl). The short‐duration flashes were recorded in cells where high reflectivity reached high altitude. Detailed analysis showed that the ONERA and NLDN reports were temporally and spatially consistent in the measurement of the cloud‐to‐ground flashes. Finally, we developed a new technique to distinguish negative CG flashes from other flashes by identifying the VHF signature of the negative downward stepped leader‐return stroke process in the flash VHF signal.