资源环境科技发展态势分析平台

Isolated breakdown process (also known as attempted leader or inverted intra‐cloud discharge) is a lightning phenomenon characterized by radiowave pulses similar to signatures of preliminary breakdown before negative cloud‐to‐ground flashes, but in this case no cloud‐to‐ground return strokes occur. We identified 128 isolated breakdown pulse trains in measurements collected in the Mediterranean by a broadband receiver (0.005‐7 MHz) in 2015 and 2018. By combining these records with concurrent Lightning Mapping Array measurements of very high frequency radiation (60‐66 MHz) emitted by in‐cloud discharges we investigate the development of each discharge. We identify two scenarios: either the discharges continue to propagate almost horizontally for more than 150 ms (73%), or they quickly fade out (27%). The geo‐localized sources of the observed isolated breakdown pulse trains, together with their waveform characteristics (duration, inter‐pulse intervals, regularity, bipolar shapes) show that both scenarios are similar to initiation processes preceding negative cloud‐to‐ground flashes.