A study of thunderstorms in south-east Queensland. Part I - meteorological aspects

Part I - Meteorological Aspects: The more recent theories of lightning formation are reviewed and some of the established meteorological facts, which are considered to be of interest to electrical engineers, discussed. The movement of thunderstorms in the Brisbane area is studied by the use of 5 minute radar photographs taken at the Electrical Engineering Department, Queensland University. The results are compared with those obtained by a previous assessment on the Darling Downs. The case for a random distribution of thunderstorms over country with no marked orography is presented and the hazards. associated with thunderstorms in south-east Queensland discussed. Part II - Electrical Aspects: Statistics relating to lightning flashes observed from the University of Queensland Lightning Observatory, classified as ground, sky and unidentified strokes, provide information on the sky to ground stroke ratio and the ground stroke density. The performances of the Pierce counter, the Linck photosensitive counter and the University of Queensland electromagnetic counter are examined. . An investigation of the rate of change of electric field (dE/dt) caused by each type of lightning stroke has been carried out and it is concluded that sky and ground strokes are probably very similar electrically; certain observed differences may be attributable to geometrical factors only. It is also concluded that the peak values of dE/dt, which occur as pulses lasting about a microsecond, arise from a. short portion of the arc 'channel at the beginning of the return stroke. Design requirements of a ground stroke-counter based on these observations are listed.