High-Speed Video Camera and Geostationary Lightning Mapper Measured Signatures of Cloud-to-Ground Strokes with and without Significant Continuing Current

Cloud-to-ground lightning return strokes are sometimes immediately followed by relatively slowly varying currents with durations that can last for hundreds of milliseconds, called continuing current. Duration of continuing current can be measured directly using high-speed video cameras and/or return-stroke channel-base current measurements. Data from the Geostationary Lightning Mappers (GLM), onboard the GOES satellites, has been suggested for use in previous studies for estimating continuing current duration using its detection of lightning optical emissions. In this study, we investigate the GLM responses to 173 negative cloud-to-ground strokes in the Space Coast of Florida from 2018-2023. We compare directly measured continuing current durations to those estimated from the GLM data. The detection efficiency of the GLM was 50.3% for cloud-to-ground strokes, with a lower detection efficiency for first strokes (31.3%) compared to subsequent strokes (62.3%). The estimated GLM continuing current durations seemed to be unrelated to those measured using high speed video cameras and/or channel-base current measurements and were significantly underestimated. It is possible that the significant underestimation found in this study compared to prior studies is due to algorithmic changes in the onboard processing of the GLM data.