Occurrence characteristics of upward lightning at the Gaisberg tower

Measurements at the instrumented Gaisberg tower (GBT) along with data from the Austrian Lightning Detection and Information System (ALDIS) have played an important role in improving our understanding of upward lightning discharges. A current measuring shunt is located at the base of a 1.5 m high air terminal on top of the GBT. Between 2000 and 2018, current waveforms of 865 flashes were recorded at the GBT, of which 823 (95%) were upward and 4 (0.5%) downward flashes. The waveforms of 38 flashes were not suitable for analysis. The majority (66%) of upward flashes at the GBT occurred during the non-convective season. Also, the proportion of upward lightning at the tower relative to all cloud-to-ground flashes in Austria (reported by ALDIS) was much higher during the non-convective season than during the convective season.