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We have analyzed parameters of 457 upward-initiated negative lightning flashes to the Gaisberg tower (GBT) in Austria recorded from 2000 to 2007. Lightning to the radio tower of a height of 100 m and located on a mountain 1287 m above sea level occurs almost independent of season, although a pronounced thunderstorm season exists in Austria during the summer months. A total of 30% of the upward-initiated negative flashes exhibited one or more return strokes with an average multiplicity of 4.4 and a geometric mean interstroke interval of 17.3 ms. The remaining 70% of upward-initiated negative flashes showed an initial continuous current (ICC) only, either with (22%) or without (48%) superimposed current pulses of peak currents greater than 2 kA. Median of total transferred charge to ground is about 30% lower in summer (26.8 C) than in other seasons (39.0 C). For the return stroke current pulses, we determined a median peak current of 9.2 kA (sigmalog10 = 0.25) and a median pulse charge of 0.51 C (sigmalog10 = 0.39). For current pulses superimposed on the ICC, we determined a median of 4.2 kA (sigmalog10 = 0.26) with 22 kA peak current measured for the largest ICC pulse.
Electromagnetic Compatibility, IEEE Transactions on (Volume:51 , Issue: 3 )
Date of Publication: Aug. 2009