April 8, 2004

Livermore Scientists Contribute to New Measurements of Stratospheric Ozone Present in the Upper Troposphere

LIVERMORE, Calif. - A team of scientists, including two from the Lawrence Livermore National Laboratory, have identified a new method to measure the amount of stratospheric ozone that is present at any given time in the upper troposphere.

Working with researchers from the National Oceanic and Atmospheric Administration, the University of Colorado, the Jet Propulsion Laboratory, the National Center for Atmospheric Research, NASA Ames Research Center and Harvard University, atmospheric scientists Cyndi Atherton and Dan Bergmann successfully quantified ozone transport down from the stratosphere during NASA's 2002 CRYSTAL-FACE mission over Florida.

The research is presented in the April 9 edition of the journal Science.

The atmosphere has several levels: the lowest is the turbulently mixed troposphere, which extends from the Earth's surface up to approximately 10 kilometers, and the second level is the more stable stratosphere, which extends from 10 to 50 kilometers above the surface and contains 90 percent of the world’s ozone. The tropopause is the transition zone between the two and is approximately the altitude of commercial aircraft flight.

A team of scientists within LLNL's Atmospheric Science Division created a computer model that can simulate how both ozone (O3) and hydrogen chloride (HCl) in the stratosphere travel downward across the tropopause and into the upper troposphere. Atherton and Bergmann used this model to simulate specific atmospheric events. These results, when compared to measurements, validated a novel technique that uses HCl
measurements to better understand the contribution of the stratosphere to upper tropospheric ozone concentrations. Upper tropospheric ozone plays an important role in global warming and climate change.

Ozone is a highly reactive and toxic gas. Although it blocks incoming harmful radiation, it also acts as a greenhouse gas, respiratory irritant, and can damage materials and crops.

"This research shows that there are times when a significant amount of the ozone found in the upper troposphere was due to stratosphere-to-troposphere transport events," Atherton said. "Continued use of this measurement method will lead to a better understanding of how much of this material is transported to the upper troposphere, where it affects climate and the chemical balance of the atmosphere."

Until now, no experimental technique could reliably quantify stratospheric ozone in the upper troposphere.

Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy's National Nuclear Security Administration.