New World Meteorological Organization Certified Megaflash Lightning Extremes for Flash Distance (709 km) and Duration (16.73 s) Recorded From Space

Bulletin of the American Meteorological Society

2021

Section: Introductionmentioning

confidence: 86%

Section: Measuring Lightning Flash Extent and Duration With Glmmentioning

confidence: 99%

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Where Are the Most Extraordinary Lightning Megaflashes in the Americas?

Bulletin of the American Meteorological Society

2021

“…centroids (red boxes) rather than events to document lateral flash development (Peterson et al, 2018;Peterson, 2019b;Peterson et al, 2020). Group centroid positions are less sensitive to the brightness of the optical pulse and the background radiance of the scene than the individual events.…”

Section: Accepted Articlementioning

confidence: 99%

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

Earth and Space Science

2021

Self Cite

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 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) and possibly location accuracy (LA). Radiant lightning emissions that illuminate large cloud top areas are used to examine scenarios where clouds block light from reaching orbit. In some cases, these anomalies in the spatial radiance distribution from the lightning pulse lead to “holes” in the optical lightning flash where certain pixels fail to trigger. Such holes are identified algorithmically in the Tropical Rainfall Measuring Mission satellite LIS record 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 and LA.

“…Our analysis of the most energetic GLM lightning will complement Turman's (1977) analysis of the most powerful lightning by highlighting cases of strong illumination over long periods of time (hundreds of microseconds to milliseconds). We anticipate that the GLM sample will consist of more stratiform megaflash lighting cases (Lyons et al, 2019; Peterson, 2019; Peterson, Lang, et al, 2020) than Turman's analysis (particularly, high peak current + CGs), causing the geospatial distribution of energetic superbolts to shift toward the Americas hotspots for Mesoscale Convective Systems (MCSs). Following our FORTE PDD peak optical power results (Peterson & Kirkland, 2020), we further expect that superbolts resulting from normal lightning that happens to have a relatively clear sight line to the sensor will be frequent at lower energy levels (near the minimum superbolt threshold), while the most energetic superbolts will be almost exclusively + CGs.…”

Section: Introductionmentioning

confidence: 99%

GLM Observations of the Brightest Lightning in the Americas

Lay

2020

JGR Atmospheres

Self Cite

Two years of Geostationary Lightning Mapper (GLM) science data are used to document the brightest lighting flashes observed on the Americas continent. The most radiant optical lightning emissions-termed "superbolts"-were first identified by the Vela satellite constellation in the 1970s (Turman, 1977, https://doi.org/10.1029/JC082i018p02566) and are defined in terms of peak optical power. GLM is an integrating sensor that, instead, measures the total optical energy from a lightning pulse. While GLM might not correctly classify short-duration superbolts, its top lightning cases certainly fall in the superbolt category, and the wealth of GLM measurements over its stationary hemispheric field of view provide an unmatched sample of extraordinarily bright lightning. While radiant bolts in excess of 100× the optical energy of typical lightning are ubiquitous across the Americas and result from many types of lightning processes, we find the most radiant cases (>1,000×) are concentrated in the central United States and in the La Plata basin in South America. Coincident Earth Networks Global Lightning Network (ENGLN) observations reveal that these extremely bright emissions usually result from + CG strokes with high peak currents in long horizontal flashes outside of the convective core. Single cases of these megaflashes might produce multiple superbolts over their durations. Plain Language Summary Where is the brightest lightning in the Americas? The Geostationary Lightning Mapper (GLM) measures the optical energy of lightning from space. We use 2 years of continuous staring measurements from across the continent to identify the top cases of lightning "superbolts"-optical emissions from lightning that are at least 100× brighter than normal. GLM confirms past findings that a myriad of lighting processes can produce a superbolt: Intracloud pulses and Cloud-to-Ground strokes with a range of peak currents. However, the absolute brightest cases-at least 1,000× more energetic than normal-cluster in certain regions known for very large thunderstorms. The superbolts in these Mesoscale Convective Systems (MCSs) often occur with "megaflash" lighting that develop horizontally over hundreds of kilometers and are associated with intense + CG discharges.