Page 2/3 - Posted July 16, 2010
Uncertainty also still exists on just how rapidly ozone loss occurs early in the process, according to Linnea Avallone , who is also using the CNES balloon platform to carry her instruments into the stratosphere.
The current computer simulations that model ozone loss do well enough over the length of the season, but don’t quite get it right in the beginning, Avallone explained. What’s happening in the early weeks of chemical havoc in the stratosphere will become increasingly important as the ozone hole heals. That’s because scientists’ ability to forecast ozone depletion will hinge on those details, she said.
“We’re hoping by making these measurements in a particular air mass that we’re following for a long time, we’ll be able to get some better constraints on why ozone is lost and the rate it’s lost,” said Avallone, an associate professor in the Department of Atmospheric and Oceanic Sciences at University of Colorado in Boulder .
Based on model predictions of the consequences of the Montreal Protocol, which barred the use of ozone depleting substances such as chlorofluorocarbons, the annual ozone hole over Antarctica is expected to “close” back to pre-1980s levels by mid-century.
Free-floating and free-falling
The ozone hole research is only part of the Concordiasi story.
About two-thirds of the balloons will carry instruments that will measure various atmospheric properties, such as temperature, pressure, humidity and winds in a region where such data are still very scarce, according to Stephen Cohn , a scientist at the National Center for Atmospheric Research (NCAR) .
NCAR will fly an instrument package called a driftsonde on the balloon gondola that will release sensors, or dropsondes, that will parachute from about 20 kilometers to the ground in about 20 minutes. Each driftsonde can carry up to 50 dropsondes that it can drop by remote command.
“We get a full profile of the atmosphere from it,” Cohn explained. “It’s very different from a balloon flight where you’re only getting measurements from the flight level.”
The data from the dropsondes will help scientists tweak the data coming from satellites to ensure that what those orbiting eyes see in the lower atmosphere from outer space reflects reality.
“There’s really a dearth of observations at both poles. This is going to be a lot more measurements of what the atmosphere is really doing,” Cohn said.
Other techniques for measuring atmospheric properties include using GPS receivers on the gondolas, using a technique called radio occultation. Jennifer Haase at Purdue University has a Small Grant for Exploratory Research from the National Science Foundation for this part of the Concordiasi project.
As the line of sight of the GPS signal from any of the orbiting global positioning satellites passes deeper into the atmosphere, the signal path is refracted — bent and delayed — by the density changes in the atmosphere. The refraction is measured by the Doppler shift of the carrier frequency of the GPS signal, providing information on the pressure, temperature and humidity structure of the atmosphere.
The usefulness of the data from the dropsondes, GPS and other instruments goes beyond better operational weather forecasts for the next week. Rabier noted that eventually improving confidence in the use of satellite measurements will feed into climate models that account for long-term changes, such as the continental precipitation, that affect the growth and stability of Antarctica’s vast ice sheets.
“A critical issue for society is whether climate change can result in a significant change of the mass budget of the Antarctic ice sheet and, consequently, can impact global sea-level,” she said.
Antarctica holds about 70 percent of the world’s fresh water — enough to raise sea level by about 60 meters if it were possible to melt all at once, which would flood and devastate coastal regions around the world. While that scenario is unlikely, many scientists believe the sea level could rise by at least a meter by 2100. Antarctica will likely be an important part of that equation.Back 1 2 3 Next