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Sore Throat
Joined: 01 Sep 2000
Posts: 1802
Location: x |
Pollution May Act As Antifreeze in Clouds
 Fri Jan 23, 2004 3:01 am
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Ah yes, "Those wispy cirrus clouds that float high in the sky"...
how well I've come to know thee...
http://story.news.yahoo.com/news?tmpl=story&u=/ap/20040122/ap_on_sc/cloud_antifreeze_1
Pollution May Act As Antifreeze in Clouds
By RANDOLPH E. SCHMID, Associated Press Writer
WASHINGTON - Those wispy cirrus clouds that float high in the sky may be thinning out due to nitric acid pollution, a change that scientists say could affect climate.
Airborne measurements of the high clouds taken in the summer of 2002 showed increased humidity in the clouds and found nitric oxide, which is a pollutant that comes from jet exhaust, combustion on the ground and other sources, according to a paper in Friday's issue of the journal Science.
Clouds are a major factor in climate, said Ru-shan Gao of the National Oceanic and Atmospheric Administration's Aeronomy Laboratory in Boulder, Colo.
Gao, lead author of the study, said the impact of changes in these clouds, drifting 9 miles above the ground, still must be assessed.
The clouds will be thinner, he said. That could mean more sunlight is allowed in, warming the Earth. It also could mean more infrared radiation from the ground escapes into space, resulting in a cooling.
The nitric acid appears to act a bit like antifreeze, preventing the ice crystals that it coats from growing to their full size by absorbing water vapor from the air. That results in smaller ice crystals in the clouds and higher humidity.
They found the effect at temperatures lower than 96 degrees below zero Fahrenheit.
Further sampling of high cirrus clouds is planned to confirm the findings, Gao said.
Thomas P. Ackerman, chief scientist in atmospheric radiation at the Energy Department's Pacific Northwest National Laboratory, welcomed the report as "the beginning of the discussion."
He noted, however, that high relative humidity has also been reported in cirrus clouds at somewhat warmer temperatures — minus 70 degrees or so — which he said cannot be explained by the same method the researchers propose for their colder readings.
"It's an interesting study, but it has to be extended to higher temperatures to explain the observations," he said.
Clouds are constantly changing and a lot more needs to be known about how ice crystals grow and shrink, added Ackerman, who was not part of the research group.
[Edited 3 times, lastly by Sore Throat on 01-22-2004] |
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halva
Joined: 04 Apr 2003
Posts: 513
Location: Greece |
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Sun Jan 25, 2004 5:43 am
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One thing I am not clear about is the relative role played by sulphates and by metals such as barium and aluminium, in these 'mitigation' efforts. |
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