Evaluation of the GOES-R Geostationary Lightning Mapper (GLM) Using Ground-Based Lightning Mapping Array (LMA) Observations

Observations from 3-dimensional VHF lightning mapping arrays (LMAs) provide a valuable basis for evaluating the spatial accuracy and detection efficiencies of observations from the recently launched, optical-based Geosynchronous Lightning Mapper (GLM). In this presentation, we describe results of comparing the LMA and GLM observations.

First, the observations are compared spatially and temporally at the individual event (pixel) level for sets of individual discharges. For LMA networks in Florida, Colorado, Texas, and Oklahoma, the GLM observations are well correlated in time and position with LMA observations. The graphical comparisons show a location uncertainty depending on the altitude at which the scattered light is emitted from the parent cloud. An offset is seen due to the viewing parallax when the lightning altitude is different that the cloud top model.

Detection efficiencies (DEs) can be accurately determined graphically for intervals where individual flashes in a storm are resolved time-wise, and DEs and false alarm rates can be automated using flash sorting algorithms for overall and/or larger storms. This can be done as a function of flash size and duration, and generally shows low detection rates for larger flashes. Initial results showed decreased detection efficiency if the storm is thick and has multiple lightning layers.