An update on the charaterictics of positive flashes recorded on the Säntis Tower

摘要

We present an update on the characteristics of positive flashes recorded on the Säntis Tower in Switzerland from May 2010 to January 2013, during which period 38 positive flashes were recorded. Out of the 38 recorded flashes, 1 was identified as a normal downward flash, 5 were classified as type-1 flashes (characterized by a large unipolar impulse) and the rest of the flashes (32) were classified as type-2 flashes (characterized by a slow waveform with superimposed pulse train). We present a summary of the characteristics of the lightning current parameters for type-1 and type-2 flashes separately and for both types combined. We also present a comparison between the present results corresponding to type-1 flashes and Berger et al.'s data for flashes with large impulsive currents. A similar comparison is presented between type-2 flashes in this study and Berger et al.'s data for flashes without large impulsive currents. In the latter comparison, the most significant differences between the two datasets are in the peak current and the amount of transferred charge, both of which are substantially larger in our type-2 flash dataset. We finally present a discussion of the oscillatory pulse trains in type-2 flashes. Our data are found to be, in general, consistent with those observed at the Gaisberg tower. However, the overall leader pulse duration and the individual pulse duration observed at Säntis are higher than their counterparts at Gaisberg.