Characterization of positive cloud-to-ground Lightning Discharges

We examined 52 positive cloud-to-ground flashes containing 63 return strokes recorded in Gainesville, Florida, in 2007-2008. The U.S. National Lightning Detection Network located 51 (96%) of the positive return strokes at distances of 7.8 to 157 km from the field measuring station and correctly identified 48 (91%) of them as cloud-to-ground discharges. The average number of strokes per flash (multiplicity) is 1.2. In three (38%) of eight two-stroke flashes, the second stroke likely followed the channel of the first stroke and in five (62%) flashes it likely created a new termination on ground . The characteristics of positive return-stroke electric field and field derivative waveforms are analyzed. The GM values of initial electric field peak normalized to 100 km for 48 positive return strokes and corresponding NLDN-reported peak current are 18.1 V/m and 74.6 kA, respectively.