Holes in Optical Lightning Flashes: Identifying Poorly-Transmissive Clouds in Lightning Imager Data

Abstract

Recent analyses of geostationary lightning mapper (GLM: Goodman et al., 2013; Rudlosky et al,. 2019) observations from NOAA's Geostationary Operational Environmental Satellites (GOES) have revealed that while GLM meets its required specifications for detection over 24 h (Bateman & Mach, 2020), there are drastic reductions in DE in certain storms compared to ground-based radio-frequency lightning locating systems (i.e., Bitzer, 2019; Rutledge et al., 2019; Said & Murphey, 2019; Thomas, 2019). Differences in instrument performance between GLM and the ground networks has been attributed to detection physics. Radio-Frequency (RF) emissions from lightning escape the cloud unimpeded, while the optical emissions that GLM measures interact with the cloud medium through scattering and absorption. Computational models have shown how optical emissions are diluted in space and delayed in time as the result of scattering in various cloud geometries (

Combined Optical and Radio‐Frequency Perspectives on a Hybrid Cloud‐To‐Ground Lightning Flash Observed by the FORTE Satellite

“…We have noted this behavior before with LIS flashes (Figure 1 in Peterson & Liu, 2013 is one example) where coincident radar data show that such optical holes correspond to dense convective cells embedded in the flash footprint that seem to block radiance from reaching the satellite. Dark pixels causing “holes” in otherwise contiguous flash footprints during intense low‐altitude processes provides further evidence that clouds modify the optical signals recorded from orbit – even to the point of preventing detection (Peterson, 2021). The pixels corresponding to the hole were illuminated during earlier periods of the flash dominated by high‐altitude IC pulses (including in Figure 7c), and thus the hole is not observed in Figure 4c.…”