Grease lightning

 

Out of the 1.2 billion lightning flashes that occur in the world, NASA has found that each flash produces a puff of nitrogen oxide (NOx) that reacts with sunlight and other gases in the atmosphere to produce ozone.

When ozone is near the Earth’s surface, it can harm human and plant health, but when it’s found higher in the atmosphere, it is a potent greenhouse gas.

"There's still a lot of uncertainty about how much NOx lightning produces," said Kenneth Pickering, an atmospheric scientist who studies lightning at NASA's Goddard Space Flight Center in the US. "Indeed, even recent published estimates of lightning's global NOx production still vary by as much as a factor of four. We're trying to narrow that uncertainty in order to improve the accuracy of both global climate models and regional air quality models."

Pickering and Goddard colleague Lesley Ott are using data retrieved from aircraft and satellite observations to take steps towards making better global estimates of lightning produced NOx. They found that each flash of lightning in mid-latitude and subtropical thunderstorms turns seven kilogrammes of nitrogen into chemically reactive NOx, on average.

“In other words, you could drive a new car across the United States more than 50 times and still produce less than half as much NOx as an average lightning flash," Ott said.

The team multiplied the number of lightning strokes worldwide by seven kilogrammes and found the total amount of NOx produced by lightning each year is 8.6 terragrams, or 8.6 million metric tons. "That's somewhat high compared to previous estimates," said Pickering.

The results of this study are published in the Journal of Geophysical Research.

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