The influence of meteorological conditions on upward lightning initiation at the Gaisberg Tower

Meteorological parameters associated with the initiation of upward lightning discharges from a tall tower were investigated. The parameters, including temperature, wind speed, air pressure, and relative humidity, were measured at the Gaisberg Tower top and at a distance of 170 m from the tower. A comparison of parameters associated with self-initiated upward flashes (initiated without any nearby preceding lightning activity) and nearby-lightning-triggered upward flashes (triggered by nearby preceding lightning activity) was made. It shows that at the Gaisberg Tower (GBT), relatively low ambient temperature facilitates to initiate upward flashes without any nearby preceding lightning activity. Relatively high ambient temperature (8.5 °C to 15.5 °C) facilitates to initiate upward positive stepped leaders, rather than the common continuous leaders, in the self-initiated upward negative flashes. No reliable correlation between wind speed and upward initiation of lightning was found.