A new study has found that superbolts are more likely to strike as the electrical charge region of the storm cloud approaches the land or ocean surface. These conditions are responsible for super hot spots over some oceans and high mountains.

Superbolts make up less than 1% of the total amount of lightning, but they pack a powerful punch when they strike. The average power of a lightning strike is about 300 million volts, but superbolts are 1,000 times stronger and can cause serious damage to infrastructure and ships, according to the authors.

“Superbolts are a remarkable phenomenon, even though they account for only a small percentage of all lightning strikes,” said Avihai Ephraim, a physicist at the Hebrew University of Jerusalem and lead author of the study.

A 2019 report found that superbolts tend to be concentrated over the northeastern Atlantic Ocean, the Mediterranean Sea, and the Altiplano, one of the highest plateaus on Earth, in Peru and Bolivia. “We wanted to know why these powerful super stars are more likely to form in some places than others,” Ephraim said.

A new study provides the first description of the formation and distribution of superbolts on land and sea worldwide. The research was published in the Journal of Geophysical Research: Atmosphere.

Thunder clouds often reach heights of 12 to 18 kilometers (7.5 to 11 mi) and cover a wide temperature range. However, for lightning to occur, the cloud must pass the line where the air temperature reaches 0 degrees Celsius (32 degrees Fahrenheit). Above the frost line, electrification occurs in the upper parts of the cloud, creating a “charge zone” of lightning. Ephraim questioned whether changes in the height of the frost line and the resulting elevation of the load zone would affect the storm’s ability to produce superbolts.

Previous studies have examined whether sea spray, shipping lane emissions, ocean salinity, and even desert dust affect the strength of superbolts, but these studies were limited to regional water bodies and could only explain part of the regional distribution of superbolts. The global explanation for Superbolt hotspots remained unclear.

To determine what causes super stars to cluster in specific areas, Ephraim and his co-authors needed to know the time, location and energy of selected lightning strikes, which they obtained using an array of radio wave detectors.

They used this lightning data to extract key characteristics of the hurricane environment, including land and water surface elevation, head zone elevation, cloud top and bottom temperatures, and aerosol concentrations. They then investigated the correlations between each of these factors and the strength of the superbolt and got an idea of ​​what produces stronger lightning and what does not.

The researchers found that, unlike previous studies, aerosols did not affect the strength of superbolts. Instead, the shortening of the distance between the charge area and the ground or water surface caused a significant increase in lightning voltage. Near-surface storms allow higher energy discharges to occur because generally shorter distance means less electrical resistance and therefore higher current. And higher current means stronger lightning.

The three regions with the most supershocks (northeast Atlantic, Mediterranean, and Altiplano) have something in common: lightning load zones and short gaps between surfaces.

“The correlation we saw was very clear and significant, and it was very pleasing to see it in three regions,” Ephraim said. “This is a big breakthrough for us.”

Knowing that the shorter distance between the surface and the cloud’s charge region leads to more superlightning will help scientists determine how climate change may affect superlightning in the future. Warmer temperatures can lead to weaker lightning, but more moisture in the atmosphere can prevent this, Ephraim said. There is no final answer at this time.

In the future, the team plans to study other factors that may contribute to the formation of superbolts, such as changes in the magnetic field or solar cycle.

“There are a lot more unknowns, but what we found here is a big piece of the puzzle,” Ephraim said. “And we’re not done yet. We still have a lot of work to do.” Source