Comparison of High‐Speed Optical Observations of a Lightning Flash From Space and the Ground

Oscar A Van Der Velde,Olivier Chanrion,Torsten Neubert,Steven Goodman,Ferran Fabró,Joan Montanyà,Nikolai Østgaard,Jesús A López,Victor Reglero

doi:10.1029/2020ea001249

Abstract

AbstractWe analyze a nighttime negative cloud‐to‐ground lightning flash in Colombia observed from the ground with a high‐speed camera at 5,000 images per second and from space by the Atmosphere‐Space Interactions Monitor (ASIM) on the International Space Station (ISS), the Lightning Imaging Sensor also on the ISS (ISS‐LIS), and the Geostationary Lightning Mapper (GLM) on GOES‐16. The space instruments measure the oxygen band at 777.4 nm, allowing for direct comparisons of measurements, and the ground‐based camera observes in a wide visible band. After conversion to energy emitted at the cloud top, we find a good linear correspondence of the optical energies measured by the three space instruments, except that GLM values were 3 times higher. We attribute this mainly to the difference in viewing angles between spacecraft and the cloud. Over the entirety of the ASIM observed flash, optical pulses were detected by GLM and LIS, only when the energy reported by ASIM was greater than 332 J and 949 J, respectively. Their detection rate corresponds to 14% and 2.5%, respectively, of the flash duration observed by ASIM. The temporal variation of the high‐speed camera luminosity matched well the features observed by ASIM around the time of the stroke but reached ~3.9 times higher peak intensity during the return stroke, attributed to its broader spectral sensitivity band and a viewing angle advantage.

Highlights

The first dedicated instruments in space for global mapping of lightning flashes were the Optical Transient Detector on MicroLab‐1, launched in 1995, and the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measurement Mission satellite, launched in 1997 (Boccippio et al, 2002; Christian et al, 1989)
After conversion to energy emitted at the cloud top, we find a good linear correspondence of the optical energies measured by the three space instruments, except that Geostationary Lightning Mapper (GLM) values were 3 times higher
The analysis of optical emissions produced by a lightning flash observed from space shows a consistent image footprint among the three different space instruments, with GLM showing the largest area in agreement with its slightly better pixel sensitivity

Summary

Introduction

The first dedicated instruments in space for global mapping of lightning flashes were the Optical Transient Detector on MicroLab‐1, launched in 1995, and the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measurement Mission satellite, launched in 1997 (Boccippio et al, 2002; Christian et al, 1989). The imagers of these missions monitor a narrow 777.4 nm oxygen triplet band containing the bright emissions by lightning that allow for lightning detection both day and night (Christian & Goodman, 1987; Goodman et al, 1988). Since the GLM and the LI will be used operationally for the two decades, it is of interest to understand their sensitivities to various lightning and cloud properties (e.g., Erdmann et al, 2020)

Methods

Results

Conclusion