Study: Thunderstorms Rain Down Ozone

By Brittany Patterson, E&E reporter

January 15,2015; 8:00AM,EST

 

 

 

The mighty power of a thunderstorm might fill some of us with awe and dread, but what's happening up in the atmosphere during the booms and flashes has implications for climate change, a new study says.
Research published in the journal Geophysical Research Letters shows that large storms move significant amounts of ozone from the stratosphere down to the troposphere, or the part of the atmosphere closest to Earth.
It's a phenomenon that has long been observed by other researchers studying atmospheric sciences, but never proved until now.
"The biggest, most violent thunderstorms bring natural ozone down from the stratosphere, but transform local air pollution problems into hemispheric climate problems," said Russell Dickerson, professor of atmospheric and oceanic science at the University of Maryland, who did not work on the paper but has studied thunderstorms and the ozone layer.
On May 30, 2012, a research aircraft carrying a piece of equipment called a Differential Absorption Lidar, or DIAL, which is used to measure ozone, flew into a series of thunderstorms above Kansas. During the flight, the equipment picked up a "curtain of ozone" that resembled a "ram's horn" dipping from the stratosphere into the troposphere. The amount of ozone inside the ram's horn area measured 150 parts per billion by volume of ozone and extended about 2.5 miles into the troposphere. At the same altitudes, away from the thunderstorm, ozone levels were measured between 60 to 100 parts per billion.
The researchers later re-created the phenomenon in a simulation.
Thunderstorm over Winterthur / Zurich (Switzerland). (Credit: Flickr/Kuster & Wildhaber Photography)
Huge chemical reactions in the sky
"It has big impacts for climate change," said Shawn Honomichl, an associate scientist at the National Center for Atmospheric Research and a co-author of the paper. With any large thunderstorm, or mesoscale convective system larger than 62 miles in size, Honomichl said large concentrations of ozone could move from the stratosphere into the troposphere.
"This movement causes chemical reactions that affects all the other chemistry inside the troposphere," he said.
Statospheric ozone, or what we commonly call the ozone layer, is actually good for humans. It's naturally occurring ozone that shields us from ultraviolet radiation.
Tropospheric ozone, commonly called smog, is man-made ozone and has the ability to destroy living tissue and cause respiratory problems.
The discovery of this phenomenon throws into question the accuracy of modern global climate models and could have implications for human health, especially as climate change increases the prevalence of thunderstorms.
Hundreds of large storms like the one studied occur in the United States every summer, and the frequency of them is expected to increase. A 2007 study found that the number of severe thunderstorms in the United States is expected to increase, and a study released last year in Science asserted the United States can expect the number of lightning strikes to increase by about 12 percent for every degree of rise in global average air temperature.
Some news for climate models
Current climate models do not account for ozone being moved into the troposphere from thunderstorms, in part because computers do not yet have the capability, but the authors say that in light of a changing climate, it's important to incorporate this phenomenon.
"With current climate models that do not take into account this phenomenon, the ozone is budgeted to another location than where it actually is," Honomichl said. Since ozone becomes harmful in concentrated levels, which often happens on a regional level, better models could give officials a more accurate picture of climate and could help health officials better prepare for days with heavy ozone levels.
This paper does not conflict with the scientifically held belief that the dominant source of ozone on the planet comes from man-made air pollution, Dickerson added.
Because ozone levels vary so greatly by region, it's hard to get solid numbers on how many people exposure can affect, but U.S. EPA literature states that people with lung diseases, children and older adults are all more sensitive to elevated ozone levels.
"This paper basically says that the interaction of thunderstorms and climate is more complex than we previously thought and it's very difficult to simulate," Dickerson said. "The impacts are real, and the take-home message is that we can't rest on our laurels. We have to continue to improve climate models."
The research was funded by the National Science Foundation and NASA.
Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.
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