First validation of the Lightning Imager on board Meteosat Third Generation with Earth Networks Total Lightning Network

The Lightning Imager (LI), onboard the newly launched Meteosat Third Generation (MTG) satellite, represents a major advancement in spaceborne optical lightning detection over Europe, Africa, and partly also South America. Although an estimate of the detection efficiency of the LI instrument is theoretically known, its validation under realistic conditions is very necessary and desirable for future calibration purposes. This study presents the first validation of LI detections using data from the Earth Networks Total Lightning Network (ENTLN), a ground-based system that observes both intra-cloud and cloud-to-ground lightning. The validation will be performed for the period of October 2024 over eastern South America, an area with frequent and diverse convective activity. To ensure accurate spatial comparison, LI flash locations will be corrected for parallax displacement prior to validation. A spatiotemporal coincidence matching algorithm will be employed to associate LI and ENTLN flashes, allowing for small spatial and temporal offsets rather than requiring exact matches. Subsequently, various verification metrics, such as detection efficiency, false alarm rate and detection ratio will be computed based on the matched events. In addition, a temporal analysis will be performed using hourly total lightning flash counts, including a comparison of diurnal cycle to assess temporal consistency between the two datasets. Based on the simplifying assumption that brighter optical flashes generally correspond to stronger electrical activity, the study will further investigate the relationship between LI-measured radiance and peak current derived from ENTLN.