Accurate measurements of global lightning are essential for understanding present and future atmospheric electricity, composition, and climate. The latest space‐based lightning detector, the Geostationary Lightning Mapper (GLM), was the first to be placed in geostationary orbit, with a continuous view of most of the American continents. Prior to the GLM, the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite collected lightning measurements from which numerous lightning climatologies have been developed, including those used in global models. However, this study finds that both the GLM and a second, similar LIS placed on the International Space Station (ISS) in 2017 detect lightning at similar rates and are undercounting lightning compared to ground‐based Lightning Mapping Arrays (LMAs). The GLM undercounts lightning by an average factor of 7.0, reaching a maximum over 120 as a function of satellite zenith angle, radar reflectivity at a height where the temperature is −10°C, flash height, and thunderstorm polarity. The LIS is estimated to undercount lightning by an average factor of 5.6, reaching a maximum of 75.0 as a function of radar reflectivity at the −10°C level, flash height, and thunderstorm polarity. Preliminary predictive equations for the GLM and LIS lightning undercount factor, or scaling factor (SF), use ice‐water content, equilibrium level, flash height, and satellite zenith angle, all of which can be derived in models. These equations are developed to encourage updating lightning parameterizations within global models and will likely increase modeled lightning's effects on atmospheric electrical circuits, composition, chemistry, and climate change.
A longstanding question for scientists has been whether or not any observable trends or shifts in global lightning activity have occurred since the Industrial Revolution. This study utilized over 8,000 certified ground‐based stations over a 43‐year period, as well as 16 years of Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) data, to provide a better understanding of the processes behind these trends. Ground station results show that many global regions have observed significant increases or decreases in thunder day occurrence. The Amazon, Maritime Continent, India, Congo, Central America, and Argentina display increases in annual thunder days since the 1970s, whereas China, Australia, and the Sahel among others observe decreases in the number of thunder days. The corresponding change in lightning flash density from the TRMM‐LIS, as well as the number of thunderstorm features and lightning flashes per thunderstorm feature, is compared to the thunder day trends during the TRMM lifespan. Results show a positive correlation between the changes of thunder day occurrence and flash density over most regions of the TRMM domain, including the Maritime Continent, China, South Africa, and Argentina. However, there are several regions with disagreements between the flash density and thunder day trends, such as India and Western Africa. The disagreements are related to the changes in the number of flashes per thunderstorm, which suggest other reasons to interpret the long term trends in thunder day occurrence over various regions. Understanding these regional trends in lightning activity is important in understanding the changes of precipitation systems under a varying climate.
more » « less- NSF-PAR ID:
- 10374718
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 124
- Issue:
- 9
- ISSN:
- 2169-897X
- Page Range / eLocation ID:
- p. 4955-4974
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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