Gretchen Cook-Anderson
Headquarters, Washington                  Dec. 15, 2004
(Phone: 202-358-0836)

John Bluck
Ames Research Center, Moffett Field, Calif.
(Phone: 650/604-5026/9000)

RELEASE: 04-397

NASA SCIENTISTS DISCUSS GIANT ATMOSPHERIC BROWN CLOUD

     NASA scientists announced a giant, smoggy atmospheric 
brown cloud, which forms over South Asia and the Indian 
Ocean, has intercontinental reach. The scientists presented 
their findings today during the American Geophysical Union 
Fall meeting in San Francisco.

The scientists discussed the massive cloud's sources, global 
movement and its implications. The brown cloud is a moving, 
persistent air mass characterized by a mixed-particle haze. 
It also contains other pollution, such as ozone.

"Ozone is a triple-threat player in the global environment. 
There are three very different ways ozone affects our lives," 
said Robert Chatfield, a scientist at NASA's Ames Research 
Center, Moffett Field, Calif. "A protective layer of good 
ozone, high in the atmosphere, shields us from deadly 
ultraviolet light that comes from the sun. Second, bad or 
smog ozone near the surface of Earth can burn our lungs and 
damage crops. In our study, we are looking at a third major 
effect of ozone, that it can warm the planet, because it is a 
powerful greenhouse gas," Chatfield said.

"We found both brown cloud pollution and natural processes 
can contribute to unhealthy levels of ozone in the 
troposphere where we live and breathe. Some ozone from the 
brown cloud rises to high enough altitudes to spread over the 
global atmosphere," Chatfield explained. Ozone from the 
Earth's protective stratospheric layer, produced by natural 
processes, can migrate down to contribute to concentrations 
in the lower atmosphere, according to the scientists.

The researchers studied the intercontinental smog ozone 
processes associated with the brown cloud over South Asia. 
They used a NASA technique that combines data acquired by 
satellites with ozone data measured by instruments on special 
weather balloons.

The ozone-monitoring instrument on NASA's Aura satellite is 
providing data about the brown cloud. "The beautiful, high-
detail images from this instrument promise to help us sort 
out our major questions about how much of the tropospheric 
ozone is from pollution and how much is from natural 
factors," Chatfield said.

Analysis shows ozone in the lower atmosphere over the Indian 
Ocean comes from the intensely developed industrial-
agricultural areas in the region. The southern pollutant 
buildup has long-range effects, often traveling across 
Africa, further than the brown cloud of particles, according 
to researchers.

To access technical information about the brown cloud study 
on the Web, visit:

http://geo.arc.nasa.gov/sgg/chatfield/recentRes.html

For information and images related to this story on the Web, 
visit: 

http://www.nasa.gov/vision/earth/environment/brown_cloud.html

For information about NASA and agency programs on the 
Internet, visit:

http://www.nasa.gov

-end-

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