Validation of the Geostationary Lightning Mapper With a Lightning Mapping Array in Argentina: Implications for Current and Future Spaceborne Lightning Observations

A validation study of the Geostationary Lightning Mapper (GLM) on board the Geostationary Operational Environmental Satellite 16 (GOES-16) was done using a ground-based lightning mapping array (LMA) deployed as part of the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign in Argentina. GLM detected lightning with 74.6% efficiency over 61 thunderstorm days in December 2018 through April 2019. However, GLM detection efficiency (DE) was negatively correlated (r = -0.49) with LMA flash rate. GLM DE also was negatively correlated with LMA flash altitude (r = -0.24), reflecting the influence of multiple competing trends. GLM DE was positively correlated (r = 0.27) with number of LMA sources in a flash, indicating improved DE for larger flashes. During periods with anomalously electrified storms, GLM DE was reduced to 50.9%. Statistics were found to be sensitive to analysis criteria, but most of the above trends remained consistent regardless of specific criteria. Because the methodology allowed a GLM flash to match more than one LMA flash, actual GLM flash rate was a factor of 2.9 lower than the LMA flash rate, and this ratio grew larger as LMA flash rate increased. A sensitivity study examined the impact of improved DE for smaller flashes; that is, an improved sensor (or algorithm) that was better able to detect and distinguish between separate small lightning flashes. The results showed improved correlation with LMA flash rates, as well as improved ability to identify lightning jumps associated with intensifying convection. Based on a comparison with a ground-based, three-dimensional lightning detection system in Argentina, the Geostationary Lightning Mapper (GLM) on board the Geostationary Operational Environmental Satellite 16 (GOES-16) detects lightning with nearly 75% efficiency, which meets its requirements. However, that detection efficiency decreases a lot when thunderstorms produce a lot of lightning at once, or small lightning flashes, or when lightning occurs deeper in the cloud where it is more difficult for the optical pulse to make its way to cloud top. This makes GLM somewhat less useful during the most intense part of a storm's life. However, if GLM or a similar sensor could be made more sensitive, either with improved hardware design or better data processing, then it would become more useful in intense storms. The Geostationary Lightning Mapper detected lightning with overall 75% efficiency relative to a ground network in ArgentinaDetection efficiency depended significantly on day/night, and on flash rate, size, altitude, and the presence of anomalous lightningAn improved sensor that could better detect and distinguish between small flashes would provide more information about storm evolution