The design and use of instruments for counting local lightning flashes

Abstract

Instruments for counting local lightning flashes are reviewed and reasons are given for selecting one particular design for extensive tests. The importance of the aerial configuration is stressed. A 7 m vertical aerial has been adopted as a standard, and the instruments have normally been adjusted to trigger on a 3-volt signal from a built-in calibrator, corresponding to a field change of about 3 volts/m.With this arrangement, on a day on which thunder is heard, there is usually a maximum hourly count exceeding 30 and a total daily count exceeding 100.The effective range of a counter is defined in statistical terms and techniques for its measurement are discussed. Preliminary estimates of the effective range are derived from observations on a few local storms in England; with the standard instrument it is about 30km. More observations are required to confirm the results, particularly in countries with frequent thunderstorms. Equipment should be standardized so far as possible.