Comparison of current characteristics of lightning strokes measured at the CN tower and at other elevated objects

Since 1991, a broadband, high-resolution current measurement system has captured the lightning current derivative at the Toronto CN Tower. In this paper, extensive statistics (1992-2001) of CN Tower lightning current waveform parameters (maximum steepness and peak) are compared with waveform parameters of currents recorded at other elevated objects, including rockets trailing conducting wires. The influence of the height of the struck object on waveform parameters is analyzed. The paper focuses on the comparison of CN Tower data with data from other tall structures as well as from rocket-triggered lightning facilities in Florida and New Mexico. The elevated structures used for the comparison include the two towers on Mount San Salvatore in Switzerland, the 160-m tower on Hoher Peissenberg Mountain in Germany and the New York Empire State Building. As the height of the elevated struck object increases, the conducted statistical analysis shows a decrease in the current peak and also points to a decrease in the current wavefront steepness. The presented statistical results will assist in the establishment of a more sophisticated approach in designing protective measures against hazards of lightning, especially from lightning occurring at tall structures or in mountainous areas.