Assessing currents of upward lightning measured in tropical regions

•Original currents of six negative upward lightning were measured at a short instrumented tower in tropical region, Brazil.•These upward lightning measured in tropical region transferred small charge, had large average current and short duration.•Correlated records of current, electric-field change, relative luminosity and video of a single event were analyzed.•Records of electric-field change available for 5 events showed that all upward events were triggered by nearby lightning.•Only one of six upward events exhibited a return stroke following the initial stage.

Negative upward lightning events in tropical regions are discussed based on the records of six currents measured recently at a short instrumented tower in Brazil. Only one event exhibited a return stroke following the initial stage. According to available correlated records of electric-field change, all events were triggered by nearby lightning. The parameters of the measured upward lightning were compared to the counterparts measured in temperate regions. They transferred small charge (typically, 6 C), had large average current (geometric mean of 271 A) and short duration (geometric mean of 18 ms). This charge coincides with the geometric mean of the charge of negative cloud-to-ground first strokes measured at the tower.