Superbolts are an extremely rare and powerful type of lightning discharge that is estimated to be a thousand times more energetic than regular lightning strikes. These bolts can release as much energy as a small atomic bomb, and they have been known to occur in thunderstorms around the world.
Unlike regular lightning bolts that travel from cloud to ground or from cloud to cloud, superbolts originate in the upper atmosphere, between 18 and 31 miles above the Earth’s surface, in a layer called the mesosphere[1]. Superbolts are thought to be caused by a different mechanism than regular lightning, and researchers are still trying to understand the exact conditions that give rise to them. Superbolts were first identified in the 1970s, but they remained largely overlooked until recently when new satellite technology allowed scientists to observe them in greater detail. Researchers have found that superbolts occur most frequently over the oceans, particularly in the tropics, and they tend to be more common during the winter months.
The term superbolt was first coined in the 1970s by Air Force Captain Bobby N. Turman. Bob Holzworth’s (professor at the University of Washington) research has advanced scientists’ understanding of this lightning since then, but the reasons why superbolts appear in different places and during different seasons than regular lightning are still a mystery.
One theory about the cause of the superbolt is related to the mesospheric gravity waves[2]. These waves can cause regions of high electric fields that can trigger lightning. Other theories involve the interaction of the Earth’s magnetic field with the electric fields in the atmosphere.
While superbolts are extremely powerful, they are also extremely rare, occurring only a few times per year in any given location. However, because of their high energy and long-range effects, they can have important impacts on the Earth’s atmosphere and climate. For example, they can create sudden increases in the concentration of nitrogen oxides in the upper atmosphere, which can affect the Earth’s ozone layer. Holzworth manages the World Wide Lightning Location Network, a research consortium that operates about 100 lightning detection stations around the world, from Antarctica to northern Finland. By seeing precisely when lightning reaches three or more different stations, the network can compare the readings to determine a lightning bolt’s size and location.
The network has operated since the early 2000s. For the new study, the researchers looked at 2 billion lightning strokes recorded between 2010 and 2018. Some 8,000 events—one in 250,000 strokes, or less than a thousandth of 1%—were confirmed superbolts.
In water, salt splits into positive and negative ions that help conduct electricity. When lightning strikes, the more ions present, the more efficiently the electrical charge is drained from the cloud. That swift discharge causes a higher peak current and a brighter flash. The research also hints at a way that climate change might lead to brighter lightning bolts. Some patches of seawater, such as in the North Atlantic, are getting fresher as ice melts, but others, notably in the subtropical Pacific, are getting saltier as evaporation ramps up under hotter air. Ocean acidification is also adding hydrogen ions to water. All those extra ions mean climate change might spark even more intense lightning—super superbolts.
The new paper shows that superbolts are most common in the Mediterranean Sea, the northeast Atlantic, and over the Andes, with lesser hotspots east of Japan, in the tropical oceans, and off the tip of South Africa. Unlike regular lightning, superbolts tend to strike over water. Superbolts, which are more common in the Northern Hemisphere, strike both hemispheres between the months of November and February.
Footnotes
- The mesosphere is a layer of Earth’s atmosphere located above the stratosphere and below the thermosphere. It extends from about 31 to 53 miles above the Earth’s surface and is characterized by low air pressure and very low temperatures, with temperatures as low as -148°F. The mesosphere is also the layer of the atmosphere where meteors burn up upon entering the Earth’s atmosphere. While the mesosphere is a relatively understudied layer of the atmosphere, it is an important area of research for scientists studying atmospheric physics and chemistry. [Back]
- Mesospheric gravity waves are disturbances that occur in the Earth’s atmosphere, specifically in the mesosphere, that propagate upward from the lower atmosphere due to the displacement of air masses. These waves can cause fluctuations in temperature, pressure, and wind speed, and can also lead to the formation of other atmospheric phenomena, such as turbulence and oscillations. Mesospheric gravity waves can be generated by a variety of sources, including thunderstorms, orographic forcing, and atmospheric instabilities, and they can have important impacts on the dynamics and chemistry of the upper atmosphere. Researchers are still working to understand the mechanisms that govern the generation and propagation of mesospheric gravity waves and their effects on the Earth’s atmosphere. [Back]
Further Reading
Sources
- “‘Superbolts’ of lightning strike when scientists least expect” Science
- “Scientists are working to solve the mysteries of superbolts, the most energetic kind of lightning — here’s what we know so far” Insider
- Cummer, S.A. et al. (2018) The detection of high-frequency mesospheric echoes from lightning superbolts. Journal of Geophysical Research: Atmospheres, 123, 2671–2687. doi 10.1002/2017JD027844.
- Rodger, C.J. et al. (2021) Superbolts: An update from the 2019 AMS lightning conference. Bulletin of the American Meteorological Society, 102, E1072-E1083. doi 10.1175/BAMS-D-20-0081.1.
- “‘Superbolts’ are real, and they flash up to 1,000 times brighter than regular lightning” Live Science
- Liu, N. et al. (2020) Global distribution and climate impacts of lightning superbolts. Nature Communications, 11, 5702. doi: 10.1038/s41467-020-19527-x.
- “Why Are Lightning ‘Superbolts’ More Common Over the Ocean?” Smithsonian Magazine
- Brasseur, G. and Solomon, S. (2005) Aeronomy of the middle atmosphere: Chemistry and physics of the stratosphere and mesosphere. Springer Science & Business Media.
- “‘Superbolts’ Have 1000x the Energy of Regular Lightning” Futurity
- Hagan, M.E. and Forbes, J.M. (2002) Migrating and nonmigrating diurnal tides in the middle and upper atmosphere excited by tropospheric latent heat release. Journal of Geophysical Research: Atmospheres, 107, AAC 3-1-AAC 3-19. doi: 10.1029/2001JD001236.
- Rapp, M. and Lübken, F.J. (2004) Modeling the middle atmosphere. Springer Science & Business Media.
