NewsMay 17, 2012

Major New Project Targets Mystery of Thunderstorms

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Andrew Freedman

By Andrew Freedman

A multifaceted air and ground-based scientific field campaign is underway in the Central and Southern U.S., with about 275 scientists, pilots, and technicians out to solve meteorological mysteries about how thunderstorms affect the chemistry of the upper atmosphere. 

The 45-day field campaign, known as the Deep Convective Clouds and Chemistry Project, or DC3, could help climate scientists fine tune their computer models and improve simulations of global warming.

The project, which involves experts from the National Oceanic and Atmospheric Administration (NOAA) and NASA, along with researchers from Germany and numerous universities, employs a wide array of assets, including ground-based research radars, sophisticated lightning mapping arrays, as well as three heavily-modified research aircraft that will help measure changes in atmospheric chemistry before, during, and after thunderstorms move through a particular region. 

Diagram of the field campaign's research platforms gathering data on a thunderstorm. Click on image for a larger version.Credit: NCAR.

All this scientific firepower is aimed at gaining a better understanding of how thunderstorms affect the formation and transport of two key atmospheric compounds that affect the climate — nitrogen oxides (NOx) and ozone. 

According to NOAA researcher Tom Ryerson, large thunderstorms act like “hoover vacuums,” sucking in surrounding air — pollutants and all — and lofting it to great heights. 

Thunderstorms eventually vent these chemicals into the upper atmosphere, where they can have a significant influence on atmospheric chemistry.

“When thunderstorms form, air near the ground has nowhere to go but up,” said Mary Barth, a principal investigator on the project from the National Center for Atmospheric Research, in a press release. “Suddenly you have an air mass at high altitude that’s full of chemicals that can produce ozone.”

Getting a better handle on the sources and movement of NOx is a priority for climate scientists, since NOx itself is a greenhouse gas that helps warm the planet, and it’s also a precursor to ozone formation. 

Ozone is created through a series of chemical reactions between nitrogen oxides, water vapor, and other gases in the presence of sunlight. Ozone in the troposphere — which is the lowest layer of the atmosphere where most weather occurs — acts as a potent greenhouse gas.

Lightning is thought to be the largest natural source of nitrogen oxides emissions. Human activities, such as burning fossil fuels for energy, also emit nitrogen oxides. 

What scientists do not fully understand, and are hoping to ascertain through this field project, is exactly how much nitrogen each bolt of lightning produces.

“We don’t think that lightning is as big [a source of nitrogen oxides] as manmade sources, but we still need to know what the baseline is,” said Don Macgorman of NOAA’s National Severe Storms Laboratory in Norman, Okla., and another one of DC3’s project coordinators.

Braving Turbulent Flights

NOAA’s Ryerson is one of many DC3 researchers that have descended upon the small town of Salina, Kan., where the research aircraft are based. Ryerson is a crew member aboard NASA's DC-8 research jet. 

NASA's DC-8 research laboratory, which is being used in the thunderstorm research project that is currently underway.Credit: NASA.

This assignment involves spending hours flying at low altitudes through turbulent air, as instruments attached to the jet capture data about air flowing into and out of the storm.

The DC-8 crew, along with a German-operated Dassault Falcon jet and an NSF/NCAR Gulfstream V, are based in Salina in order to be prepared if storms erupt in any of the study’s three target areas. These areas, in northeastern Colorado and central Oklahoma, as well as northern Alabama, were chosen because of an extensive ground-based network of weather instruments, such as cutting edge mobile radar systems and lightning mapping arrays that can complement the data gathered from the air. 

These regions also have different types of manmade and natural sources of pollutants and gases that affect atmospheric chemistry. 

“It’s going to be really fun to contrast what’s being processed by the storms from these three different regions,” said NCAR’s Barth in an interview.

The field campaign is a formidable logistical challenge, given the many teams and fast-moving research platforms involved.

It’s no easy task to arrange flight patterns while complying with changing air traffic control needs, Ryerson said. “It’s a dance we have to perform each time. It’s kind of like jazz, we have to improvise.”

The research flights themselves aren’t all that pleasant for those aboard the aircraft, either. Thunderstorms, after all, are usually something that pilots avoid, not fly close to or into.

Ryerson noted that many have already suffered from some degree of airsickness, even during the training flights. 

But that’s a price they’re willing to pay in order to gather valuable data.