Photo Courtesy: Terry Deshler

Polar stratospheric clouds form over McMurdo Station. U.S. and French scientists plan to use super-pressure balloons next season to carry instruments that will measure PSC chemistry, which could help forecast future ozone depletion.

Working with the French

Milne said the NSF is planning a large, balloon-based field campaign during the 2009-10 field season between U.S. researchers and scientists from the French space agency Centre National D’Etudes Spatiales (CNES) that will intensely investigate “the role of the southern polar vortex in both Antarctic climate and ozone loss processes.”

“This project will utilize the long-duration balloons designed and flown by [the French Space Agency] in 2005 over Antarctica,” Mercer said.

The 2005 project, an international program called Vorcore , launched long-duration balloons from McMurdo Station to study the transformation of CFCs into ozone-destroying chlorine atoms within the vortex. But instead of studying the reactions directly from a chemical perspective, the French team looked at the vortex core mechanics to see how it affected the CFCs and ozone.

In 2009, Deshler’s group will fly instruments on four of the French super-pressure balloons, which can remain in the same air mass for the duration of their flight, which may last up to three months.

Photo Credit: NASA

The 2006 ozone hole over Antarctica, the largest ever observed.

“The idea here is to measure PSCs from a platform drifting with the air currents,” Deshler said. “We are interested in capturing the initial particle development as the air cools to PSC temperatures, and to measure the rate at which solid PSC particles are nucleated in these cases. We can then also capture the evolution of the particles as they evaporate when temperatures warm.”

In particular, the team wants to learn more about the formation of nitric acid tri-hydrate (NATs), one of three particles that make up PSCs. The various PSC particles nucleate at slightly different temperatures, so knowing the conditions under which the NATs appear could help with ozone depletion forecasting around the world.

“[Two degrees Kelvin] can become the difference between having no ozone depletion and having significant ozone depletion, because that’s the difference of having no clouds and some clouds,” Deshler said.

Much work still to do

Estimates for “recovery” of the ozone hole range from 2040 to 2080, with the National Oceanic and Atmospheric Administration and NASA anticipating recovery by 2065.

Deshler cautioned that while the world has phased out CFCs, one of its primary substitutes, hydrochlorofluorocarbons (HCFCs), while less severe than CFCs, still deplete ozone. Countries like China and India, for instance, may continue to increase global concentrations of ozone-depleting substances just by their sheer volume of population and production.

“I think it’s still important to keep the world’s attention, at least partially focused, on the ozone loss story, because it isn’t over yet,” Deshler said. “We need to maintain those controls, and we need to seek even further substitutes. This is particularly true in the developing world.”

NSF-funded research in this story: Terry Deshler and Jennifer Mercer, University of Wyoming, Award No. 063694 .

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