Electric-field changes and the design of lightning-flash counters

Examples of electric-field and field-change records of lightning discharges will be discussed in relation to the design of lightning-flash counters. Correlations between stroke counts and visual observations of nocturnal lightning were found to be very poor for a stroke counter that operates on the abrupt-field-change principle. The abrupt field changes of both signs that accompany all lightning discharges make it virtually impossible to discriminate between ground and cloud flashes with stroke counters of the conventional type. A reliable total count for nocturnal lightning of both types can be obtained with a photomultiplier tube. A photomultiplier operated in coincidence with an electric-field-change meter can be utilized to discriminate against sferics and man-made interference. Conversely, if the photomultiplier and field-change meter are operated in anticoincidence, a trigger system can be constructed which will accept only sferics that originate from outside the area of visible lightning discharges.