Lightning Jump Algorithm for Proxy GOES-R Lightning Mapper Data

A lightning jump algorithm has previously been developed using lightning mapping array (LMA) data, with lightning jumps (sudden increases in flash rate for a convective cell) suggesting a likelihood of subsequent severe weather. This work aims to adapt the algorithm for use with data to be obtained in the future from the GOES-R Lightning Mapper (GLM), and to automate it. GLM is an optical sensor that will view illuminated cloud tops, which is fundamentally different from the radio frequency sources associated with lightning channels that are mapped by LMA. The horizontal resolution for GLM (~8 km) is also coarse compared to LMA. Proxy data have been developed for GLM, based on comparisons of past optical lightning data with corresponding LMA data. In this presentation, we will use the proxy GLM lightning data for objective (automated) thunderstorm cell tracking and identification of lightning jumps. Comparisons are made to lightning jumps identified from LMA, with cell tracking that is partially automated (having some subjective adjustments). The cell tracking allows cell size to vary considerably with time, which complicates identification of the flash rate tendency. In the example figure, GLM proxy flash rate (flashes per minute for the objectively defined cell) and GLM proxy flash rate density (flashes per minute per 1000 km2 unit area) are shown in the top panels. The bottom left panel has flash rate tendency (flashes per minute per minute) for 2-minute running means (solid line) and 5-minute running means (asterisks). The times of LMA-defined lightning jumps are marked with blue symbols between the left panels, and align well with peaks of GLM proxy flash rate tendency. Red triangles mark the times of severe weather reports from this cell. The cell track is mapped at lower right.