GLD360 Performance and Cloud-to-Ground Lightning Climatology

GLD360 is a global lightning locating system (LLS) built on a network of Very Low Frequency (VLF; ~1 kHz - ~50 kHz) sensors. In addition to reporting the location and time of detected cloud-to-ground (CG) return strokes and inter- and intra-cloud (IC) pulses, the network provides an estimate of the peak current and polarity of each event. In August 2018, an upgrade to the location algorithm added another parameter: CG/IC discrimination. In this paper, we provide an update to the performance metrics of GLD360 after this algorithm upgrade, including location accuracy, detection efficiency, peak current accuracy, and now classification accuracy, using reference data from precision LLSs and lightning mapping data from GLM and ISS-LIS.

We also apply the new IC/CG classification ability to improve upon earlier efforts to provide a quantitative estimate of global CG flash densities. These previous studies applied a peak current filter to remove the majority of IC pulses, using a correction factor to account for any CG flashes removed in the process. We compare global CG flash densities using both methods, and comment on the stability and sources of error intrinsic to each approach. We also compare the GLD360-derived CG flash density against ISS-LIS total lightning flash climatologies for a thematic global IC:CG ratio estimate.