A team of scientists has decoded how superbolts -- Earth’s strongest lightning -- occur.
Superbolts make up less than 1 per cent of total lightning, but when they do strike, they pack a powerful punch.
According to the new study published in the Journal of Geophysical Research: Atmospheres, superbolts are more likely to strike the closer a storm cloud’s electrical charging zone is to the land or ocean’s surface.
These conditions are responsible for superbolt “hotspots” above some oceans and tall mountains.
While the average lightning strike contains around 300 million volts, superbolts are 1,000 times stronger and can cause major damage to infrastructure and ships, said the researchers.
The new study provides the first explanation for the formation and distribution of superbolts over land and sea worldwide.
“Superbolts, even though they’re only a very, very tiny percentage of all lightning, they’re a magnificent phenomenon,” said lead author Avichay Efraim, a physicist at the Hebrew University of Jerusalem in Israel.
A 2019 report found that superbolts tend to cluster over the Northeast Atlantic Ocean, the Mediterranean Sea and the Altiplano in Peru and Bolivia, which is one of the tallest plateaus on Earth.
"We wanted to know what makes these powerful superbolts more likely to form in some places as opposed to others," Efraim said.
To determine what causes superbolts to cluster over certain areas, Efraim and team used lightning data to extract key properties from the storms’ environments, including land and water surface height, charging zone height, cloud top and base temperatures, and aerosol concentrations.
They then looked for correlations between each of these factors and superbolt strength, gleaning insights into what causes stronger lightning -- and what doesn’t.
The researchers found that contrary to previous studies, aerosols did not have a significant effect on superbolt strength.
Instead, a smaller distance between the charging zone and land or water surface led to significantly more energised lightning. Storms close to the surface allow higher-energy bolts to form because, generally, a shorter distance means less electrical resistance and therefore a higher current. And a higher current means stronger lightning bolts.
The three regions that experience the most superbolts -- the Northeast Atlantic Ocean, the Mediterranean Sea and the Altiplano -- all have one thing in common: short gaps between lightning charging zones and surfaces.
“The correlation we saw was very clear and significant, and it was very thrilling to see that it occurs in the three regions,” Efraim said. “This is a major breakthrough for us."