Evaluation of GOES-16 GLM to Lightning Mapping Arrays

The Geostationary Lightning Mapper on GOES-16 is the first operational lightning mapper flown in a geostationary orbit, which provides continuous observations of lightning. In order to make use of these data for improving nowcasting of severe weather and for data assimilation, it is important to characterize and understand the detection capabilities of GLM. Since GLM is an optical sensor, there are two primary reasons why it could fail to detect a flash observed by a ground-based radio direction-finding system. First, if a flash has low power and/or is of small size (a compact flash) it will be more difficult to detect using a space-borne optical sensor. Second, the light from the flash will undergo extinction as it passes through the ice water path (IWP) located above the flash. This paper will evaluate GLM flash extent density against lightning observations from the Colorado Lightning Mapping Array (COLMA) and the Northern Alabama Lightning Mapping Array (NALMA). The focus is on a representative sample of case studies encompassing different forms of convective organization at different times of day and night. The detection efficiency of GLM relative to LMA will be characterized in terms of the flash size estimated by the LMA and in terms of the IWP above the flash. The IWP will be calculated using Multi-Radar/Multi-Sensor (MRMS) national 3D radar mosaic using the flash height estimated by the LMA. Our results show that GLM detection is higher over Alabama storms than Colorado storms, driven mostly by the larger IWPs for Colorado storms.