Some aspects of lightning activity and related meteorological conditions

Lightning statistics are used to define a thunderstorm activity index. The index is based upon (1) the total duration and (2) the frequency of occurrence of lightning discharges. It is suggested that the horizontal extent of a storm may be inferred from the shape of the frequency-distribution curve, whereas the mean duration of discharges is related to the vertical convective activity. The bipolar thunderstorm model of Holzer and Saxon is extended to account for the occurrence of multiple discharges to ground. A relationship between the number of intracloud discharges and the total number of separate return strokes in ground discharges may be predicted from the model. Good agreement is found with the predictions in some, but not all, storms. Statistics are cited which suggest that the ratio of intracloud to cloud-to-ground discharges may reflect the type of storm (e.g., ‘frontal’ or ‘local air mass’).