Diagnostic analysis of triggered lightning with distributed acoustic sensing

Distributed acoustic sensing (DAS) was used for the first time to track the sources of acoustic signals associated with triggered lightning. A 4.2-km-long optical fiber cable, encompassing the lightning triggering site, was recast as 2100 acoustic sensors using the DAS technique to advance understanding of lightning processes. Two lightning flashes with return strokes and one without a return stroke were recorded. Thunder sources during three triggered lightning flashes were reconstructed in three-dimensional space with high precision using high-frequency DAS observations. The location accuracy near the ground surface reached ~30 m, taking high-speed video observations as reference. DAS provides an acoustic imprint of lightning polarity asymmetry. Moreover, DAS recordings revealed that thunder events mainly originate from the return stroke process rather than the leaders. Our results demonstrate that DAS, as a novel acoustic observation technology, can clearly identify and accurately locate thunder sources, yielding new insights into the origins and development of triggered lightning.