The magnitude and location of the charge centers involved in lightning discharges can be determined from the value of the accompanying gradient change at seven points at the ground. Instrumentation, calibration, observation, and analysis techniques for thus locating thunderstorm charge-centers are described. The results of the analysis are presented.
The thunderstorm is found to be bipolar, with the negative center at a mean height of 25,000 ft msl or −16C, and with the positive center located about 2000 ft above it. The occasional occurrence of a positive center below the negative center is shown by the record of the leader processes of ground discharges and from other evidence.
Comparison is made with the work of Malan and Schonland in South Africa. While the results are in substantial agreement, important differences in the nature of streamer processes and the relative location of the negative centers tapped by successive elements of a single ground discharge are noted.
The cold environment found for many of the negative charge centers (as low as −33C) strongly suggests that these centers might not have been produced by a glaze-ice mechanism. Riming and, perhaps, sublimation are probably the important processes for precipitation growth at such low temperatures.