Lightning Locators

Abstract

Locating lightning in real time is an old problem. Radio techniques developed in the early to mid‐twentieth century used crossed‐loop cathode‐ray direction finders (CRDF) that provide the bearing but not the range to the lightning source. Direction‐finding (DF) systems typically sense the radio signal, known as atmospherics , spherics , or ‘ sferics , that is emitted by lightning and that most listeners of AM radios interpret as interference, static , or radio noise . Quite generally, lightning radiates electromagnetic pulses that span an enormous range of frequencies. In this article, the radio signal refers to the portion of the electromagnetic spectrum that covers frequencies less than 3 × 10 8 kilohertz (denoted kHz), or 300 GHz, and the optical signal refers to frequencies greater than 3 × 10 8 kHz. Also, when not qualified here, electromagnetic radiation refers to the radio signal. Lightning sensing systems have important applications in meteorology. Certainly, these systems can help to detect and forecast the arrival of thunderstorms by monitoring their positions, motions, and intensities. Such systems are also important for lightning safety and for protecting natural resources in a diverse set of real‐time applications, including fire and personnel safety, aircraft routing, missile launch decisions, power grid operation, and weather forecasting. Lightning is a significant threat to people but far too often is underrated. Lightning sensing systems, especially those that detect intracloud lightning, are being investigated as tools for predicting severe thunderstorms, including tornadoes, microbursts, and hail. Lightning data are also being investigated as possible input for small‐scale numerical weather forecast models to supplement the usual observations of pressure, temperature, humidity, and winds. This article is not an exhaustive survey of all real‐time and research lightning location systems, but it provides a comprehensive overview of the topic. It is split into two major parts; the first reviews the many important concepts and defines the terminology used to describe them, and the second covers the different major types of operational lightning location systems by describing an example of each in detail. Many of the lightning facts herein are documented thoroughly in the references. The methods and detection systems reviewed in this article are also described on various World Wide Web (www) sites. The addresses for many of these sites are given.

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