Initial Geostationary Lightning Mapper Observations

Abstract The Geostationary Lightning Mapper (GLM) continuously observes lightning throughout a near‐hemispheric field of view, capturing spatiotemporal variability on unprecedented scales. This study documents GLM lightning distributions during the initial 9 months in the operational Geostationary Operational Environmental Satellite‐East position (December 2017 to August 2018). Spatial maps, summary statistics, and time series illustrate seasonal, regional, and diurnal lightning patterns. Lightning activity shifts from south to north during the study period with most lightning over land (83%). The average GLM flash extends over a 454‐km 2 area, lasts 301 ms, produces 262 fJ of optical energy, and consists of 16.4 (42.2) groups (events). On average, GLM flashes over the oceans are larger (570 km 2 ), of longer duration (345 ms), and brighter (420 fJ) than flashes over land (431 km 2 , 293 ms, and 230 fJ). The baseline values and early insights reported herein aim to guide the early development and application of GLM observations.