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Holes in Optical Lightning Flashes: Identifying Poorly-Transmissive Clouds in Lightning Imager Data
  • Michael Jay Peterson
Michael Jay Peterson
ISR-2,Los Alamos National Laboratory

Corresponding Author:[email protected]

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Space-based optical lightning sensors including the Lightning Imaging Sensor (LIS) and Geostationary Lightning Mapper (GLM) are pixelated imagers that detect lightning as transient increases in cloud-top illumination. Detection requires optical lightning emissions to escape the cloud-top to space with sufficient energy to trigger a pixel on the imaging array. Through scattering and absorption, certain clouds are able to block most light from reaching the instrument, causing a reduction in Detection Efficiency (DE). We use cases of radiant lightning emissions that illuminate large cloud-top areas to examine scenarios where clouds block light in only certain pixels on the imaging array. In some cases, these anomalies in the spatial radiance distribution from the lightning pulse leads to “holes” in the optical lightning flash where certain pixels fail to trigger, entirely. Such holes are identified algorithmically in the Tropical Rainfall Measuring Mission (TRMM) satellite LIS record over the southern Continental United States, and the microphysical properties of the coincident storm region are queried. We find that holes primarily occur in tall (IR Tb < 235 K) convection (87%) and overhanging anvil clouds (10%). The remaining 3% of holes occur in moderate-to-weak convection or in clear air breaks between stormclouds. We further demonstrate how an algorithm that assesses the spatial radiance patterns from energetic lightning pulses might be used to construct an optical transmission gridded stoplight product for GLM that could help operators identify clouds with a potentially-reduced DE.
Feb 2021Published in Earth and Space Science volume 8 issue 2. 10.1029/2020EA001294