Source Speed as a Driver of Geostationary Lightning Mapper Location Offsets

Abstract

Satellites in geostationary orbit provide continuous, hemisphere‐scale views of lightning, but each pixel covers a large area, and parallax and scattering can shift the apparent location of optical emissions. The Geostationary Lightning Mapper (GLM), aboard GOES, is an optical detector that continuously monitors lightning activity over the Western Hemisphere. Hazard mitigation benefits from real‐time lightning locations. Ground‐based networks have well‐characterized spatial characteristics, but space‐based imagers uniquely provide continuous, hemisphere‐scale monitoring. Improving confidence in space‐based lightning geolocation will broaden its use in hazard monitoring and risk assessment. We quantify the offset between GLM lightning locations and those from a ground‐based Lightning Mapping Array in Oklahoma and evaluate how sub‐flash processes are represented in GLM observations. GLM–LMA location differences reflect altitude‐dependent optical propagation, residual parallax, and the representation of moving optical sources by group centroids over finite integration periods. The largest and most variable offsets occur when luminous emitters move rapidly during a GLM integration, and therefore vary systematically with flash type and stage. Additionally, GLM group centroids provide more robust measurements of flash extent than pixel‐based methods, confirming prior work. These findings highlight the diagnostic value of cross‐platform analysis and demonstrate how space‐based lightning detection can improve climatologies, support hazard mitigation and broader atmospheric monitoring, and guide future multi‐wavelength observing systems.