Evaluating Geostationary Lightning Mapper Flash Rates Within Intense Convective Storms

S A Rutledge,A Clayton,B Fuchs,K A Hilburn,S D Miller

doi:10.1029/2020jd032827

S A Rutledge, A Clayton + Show 3 more

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https://doi.org/10.1029/2020jd032827

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Abstract

AbstractThe Geostationary Lightning Mapper (GLM) marks the first time that lightning observations at storm‐scale resolution are operationally available from geostationary orbit. We evaluate GLM detection efficiency (DE) for a special class of convective storms characterized by anomalous charge structures. These storms are anomalous as their internal layered charge structure departs from the tripole charge structure model, where midlevel negative charge is situated between upper and lower positive charge layers. Anomalous storms are characterized by extreme flash rates, low median flash heights, and intense precipitation. Ground truth information on lightning flash rates is provided by Lightning Mapping Arrays (LMA), which measure VHF radio frequency emissions produced by electrical breakdown. This study contrasts two regions: Colorado, where electrically “anomalous” storms are numerous, and Alabama, where they are rare. This study analyzes GLM DE as a function of the precipitation water path, cloud water path, and lightning properties from LMA. The GLM DE is found to vary with the geometric size of the flash and with cloud water path, the latter depending on flash height and cloud water content. Optical scattering (attenuation) by precipitation‐sized particles does not appear to be a factor since precipitation particles contain much less surface area than cloud particles. The size of the flash is correlated with its optical brightness, and the cloud water path is correlated with optical extinction. Regional differences in GLM DE remain that appear to be related to sensor viewing geometry and day versus night sensitivity differences.

Highlights

In 2016, an exciting new era for spaceborne observations of lightning began with the launch of the Geostationary Lightning Mapper (GLM; Goodman et al, 2013) as the first member of the Geostationary Operational Environmental Satellite R-series (GOES-R, named GOES-16)
Later, when we present detection efficiency (DE) vs. cloud water/ice path (CWP) for AL and cloud water in anomalous (CO) storm samples, the offsets observed between the AL and CO curves could very well be attributed to this limitation in the Advanced Baseline Imager (ABI) cloud path retrieval
We suggest that the GLM DE is low in anomalous storms due to two main factors, intense cloud water and cloud ice contents and compact flashes at mid-to-low levels in these storms

Summary

Introduction

In 2016, an exciting new era for spaceborne observations of lightning began with the launch of the Geostationary Lightning Mapper (GLM; Goodman et al, 2013) as the first member of the Geostationary Operational Environmental Satellite R-series (GOES-R, named GOES-16). Since the release of the first GLM data in spring 2017, studies have presented general aspects of GLM-detected lightning (Rudlosky et al, 2019a, Rudlosky et al, 2019b), evaluated the detection efficiency of GLM relative to the Earth Networks Total Lightning Network (ENTLN, Marchand et al, 2019), described extremely large lightning flashes in the stratiform regions of Mesoscale Convective Systems (Peterson, 2019, Lyons et al, 2019, Bruning et al, 2019), examined the sensitivity of parameters used in the algorithm that merges lightning “groups” into flashes (Mach, 2020) and assessed GLM detection using LIS and Lightning Mapping Array data (Zhang and Cummins, 2020; hereafter, ZC20). Peterson (2019) described hemispheric lightning flash rates and described an extremely large GLM-detected lightning flash with a length of 673 km Since the release of the first GLM data in spring 2017, studies have presented general aspects of GLM-detected lightning (Rudlosky et al, 2019a, Rudlosky et al, 2019b), evaluated the detection efficiency of GLM relative to the Earth Networks Total Lightning Network (ENTLN, Marchand et al, 2019), described extremely large lightning flashes in the stratiform regions of Mesoscale Convective Systems (Peterson, 2019, Lyons et al, 2019, Bruning et al, 2019), examined the sensitivity of parameters used in the algorithm that merges lightning “groups” into flashes (Mach, 2020) and assessed GLM detection using LIS and Lightning Mapping Array data (Zhang and Cummins, 2020; hereafter, ZC20). Rudlosky et al (2019a) showed that GLM clearly depicts the seasonal march of lightning across the Equator, and that spatial patterns of GLM lightning were consistent with previous studies (for example, the landocean contrast in lightning flash rates). Peterson (2019) described hemispheric lightning flash rates and described an extremely large GLM-detected lightning flash with a length of 673 km

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