Satellite Sheds Light on Earth's Highest Clouds

HAMPTON, Va. (AP) - A Hampton University professor is shedding new light on night-shining clouds that might be affected by climate change. Jim Russell is the lead scientist for the NASA-funded AIM satellite, the first to study the wispy "noctilucent" clouds, which only appear above Earth's poles.

Russell, an atmospheric science professor, has found that the clouds get brighter and stretch farther as the uppermost atmosphere gets colder. He thinks that the changes might be caused by human-generated global warming.

The Aeronomy of Ice in the Mesosphere satellite is providing the first global mapping of the cover and structure of these clouds, which coalesce as icy dust particles about 42 to 60 miles above the Earth's surface.

The mapping showed that the clouds are more sensitive to changes in the upper atmosphere than was previously thought, as they are changing in brightness and reach.

Scientists say that's why people as far south as Colorado and Utah have spotted the clouds in recent years.

Previously, they had only been visible to people in regions of northern Europe and Canada.

AIM is funded through NASA's Small Explorers program. It has a $140-million budget through May 2009, but Russell hopes to get funding to extend the research.

The satellite is now studying the clouds at the South Pole. Noctilucent clouds form only in the summer of the respective hemispheres, when, somewhat counter-intuitively, it is coldest at the highest reaches of the atmosphere.

"We want to look at long-term changes,'' said Russell, who presented his first batch of results at a recent meeting of the American Geophysical Union in San Francisco. "We have such great sensitivity that we really want to get a long-term database.''

Russell said the connection to climate change may involve changes in temperature and water vapor.

As the Earth's surface-level climate warms up, the coldest region of the atmosphere, where these clouds exist, actually gets colder. The colder it gets, the farther the clouds reach.

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