Review of upward positive and bipolar lightning flashes at the Gaisberg Tower

First instrumentation for lightning measurements at the Gaisberg Tower (GBT) has been installed in 1998. During the 10-years period from 2000-2009 a total of 652 lightning events have been recorded. Vast majority of the lightning to the GBT was upward initiated and only one record is a candidate for a downward flash when the recorded current waveform is used for discrimination between upward and downward lightning. 3% (21/652) of the flashes were bipolar and about the same number of 4% (26/652) were positive. 73% of positive and 63% of bipolar lightning was triggered by the GBT during cold season in Austria.