Space and ground-based measurements of negative cloud-to-ground strokes with and without significant continuing currents

We examined the responses of the Geostationary Lightning Mapper (GLM) onboard the Geostationary Operational Environmental Satellite-16 (GOES-16) to 174 negative cloud-to-ground (CG) return strokes in 77 flashes that occurred in Florida in 2018–2023. We recorded these strokes on high-speed video cameras from which we measured the continuing current durations. The GLM flash and stroke detection efficiencies were 80.5 and 50 %, respectively. The nighttime stroke detection efficiency was 2.4 times higher than that during the daytime (81.3 versus 33.9 %, receptively). The detection efficiencies for first strokes and single-stroke flashes were 31.3 and 30 %, respectively, which were lower than that for subsequent strokes (61.7 %). The GLM stroke detection efficiency did not depend upon the return stroke peak current reported by the U.S. National Lightning Detection Network, but it was significantly higher (64.9 versus 37.5 %) for strokes with significant (>3 ms) continuing current durations versus those without (<3 ms) such currents. Continuing current durations estimated from the GLM data were significantly underestimated and were unrelated to those measured from video camera records; none of the GLM-derived continuing current durations exceeded 6 ms, while those obtained from video camera records ranged from 0.28 to 685 ms. GLM Level 0 versus Level 2 data comparison indicates that onboard and ground processing techniques applied for noise removal may be responsible for continuing current duration underestimation and reduced first-stroke detection efficiency, respectively.