Geostationary Lightning Mapper Clustering Algorithm Stability

The stability of the operational real-time clustering algorithm for the Geostationary Lightning Mapper (GLM) was tested by measuring how it varied, in regard to flash rates, when the various temporal and spatial limits for the clustering algorithm changed. GLM is an instrument on the Geostationary Operational Environmental Satellite R-series designed to map total lightning activity continuously day and night with near-uniform storm scale spatial resolution. The results were then compared to similar variations made to the algorithms used to process the Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) data so that the science results of the three orbital optical lightning detectors (GLM, LIS, and OTD) can be compared. For temporal (200 to 1,000 ms) and spatial (8 to 64 km) variations and for storms with flash rates less than about 40 flashes per minute, the flash rates from the GLM clustering were not very sensitive to algorithm variations. One major difference between the GLM clustering methodology and those of OTD and LIS is that large groups and flashes are artificially terminated to maintain an operational product. The artificial termination of flashes and groups does not greatly change the flash rates for storms with flash rates less than about 40 flashes per minute.