Characterizing the Fraction of Light Observed by the Geostationary Lightning Mapper

Ground based lightning detection networks provide an important reference for understanding the fraction of light observed by the Geostationary Lightning Mapper (GLM). Optical lightning observations from the GLM are dependent on properties of the clouds surrounding the lightning channels. Denser clouds or storms with a thicker cloud layer reduce the amount of light observed by the GLM relative to storms with fewer hydrometeors or a thinner cloud layer. Data from the Washington D.C. lightning mapping array are compared with a gridded GLM flash extent density product to establish overall relationships. Individual case studies provide important insights into the GLM performance which can help advise users of the GLM gridded products. Procedures are being developed to better quantify GLM performance variations relative to the convective environment and satellite viewing geometry. Knowledge gained during this investigation will be used to advise National Weather Service forecasters using these data for convective forecast and warning operations.