How coronavirus lockdowns may have led to less lightning in 2020

Researchers have discovered a possible link between the coronavirus pandemic and fewer instances of lightning reported during worldwide shutdowns in the spring of 2020.

By Alaa Elassar, CNN

(CNN) -- Researchers have discovered a possible link between the coronavirus pandemic and fewer instances of lightning reported during worldwide shutdowns in the spring of 2020.

Global lightning activity decreased nearly 8% in 2020 amid lockdowns triggered by the pandemic, according to research presented in December at the annual meeting of the American Geophysical Union (AGU), a nonprofit scientific organization dedicated to promoting "discovery in Earth and space science."

Scientists who worked on the study discovered a potential cause for this drop in lightning activity: a decrease in atmospheric aerosols, tiny particles of pollution suspended in the air around us.

These aerosols -- produced through the burning of fossil fuels, among other things -- can paint a picture of what's going on across the earth's atmosphere, from weather patterns to natural and man-made events, experts say.

Aerosols have a "profound impact on the climate" because of their ability to alter the Earth's energy and balance, according to NASA -- and they can also contribute to lightning.

As countries around the world imposed quarantines, lockdowns and curfews aimed at limiting the spread of Covid-19, air pollution levels fell drastically, thereby reducing the amount of aerosols released into the air, according to the study.

Global air quality information and tech company IQAir's 2020 World Air Quality Report said human-related emissions from industry and transport fell during lockdowns, and 65% of global cities analyzed experienced better air quality in 2020 compared to 2019. Some 84% of nations polled reported air quality improvements overall.

"The aerosols help give water droplets in the atmosphere something to cling onto, so certainly having more aerosols will help potentially create conditions you need to have lightning," said Chris Vagasky, meteorologist and lightning applications manager at Vaisala, a private environmental monitoring company that tracks lightning around the world.

"Having more droplets in the atmosphere makes it possible to get those collisions of water and ice and things like that to create an electric charge imbalance, which leads to lightning."

Unstable atmosphere created an environment unfavorable to thunderstorms

Researchers from the Massachusetts Institute of Technology, Tripura University in India and Vaisala Inc., spent a three-month-long lockdown period from March to May 2020 measuring lightning activity by analyzing data from the Global Lightning Detection Network and the World Wide Lightning Location Network.

They determined the amount of aerosols in the atmosphere using satellite measurements, AGU said in a press release.

The study concluded that lightning activity and aerosols dropped significantly throughout Africa, Europe, Asia, and the Americas during the lockdown period.

Those results were supported by Vaisala's 2020 Annual Lightning Report, which recorded about 170 million lightning events in 2020 across the continental United States, down about 52 million from 2019.

This decrease in lightning marked the greatest change year-over-year ever recorded by Vaisala, according to Vagasky.

"When you look specifically at the March-May 2020 time period across the whole planet, there was higher than normal atmospheric pressure and lower than normal atmospheric instability," Vagasky told CNN.

"This created an environment across the planet that was unfavorable for thunderstorms to develop, and you need to have the right conditions for thunderstorms to develop before you can worry about the aerosols inside the clouds."

While aerosols play a major role in how much lightning we get each year, they are not the only important factor that comes into play, according to Vagasky. From large scale weather patterns to very small scale particle collisions inside of the thunderstorm, he added, it is likely that more than one specific factor resulted in a decrease in the amount of lightning produced.

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