Satellites illuminate pollution's influence...( Clouds have typically posed a proble...)

Clouds have typically posed a problem to scientists using satellites to observe the lowest part of the atmosphere, where humans live and breathe, because they block the satellite's ability to capture a clear, unobstructed view of Earth's surface. It turns out, however, that these "obstructions" are worth a closer look, as clouds and their characteristics actually serve a valuable role in Earth's climate. That closer look is now available by satellites comprising the Afternoon Constellation, or A-Train.

"The A-Train is providing a new way to examine cloud types," said Mark Schoeberl, A-Train project scientist at NASA's Goddard Space Flight Center, Greenbelt, Md.

Using data from instruments in a constellation of NASA satellites, scientists have discovered that they can see deep inside of clouds. The satellites are taking first-of-a-kind measurements, shedding new light on the link between clouds, pollution and rainfall.

Jonathan Jiang of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleagues used these A-Train sensors to find that South American clouds infused with airborne pollution classified as "polluted clouds" tend to produce less rain than their "clean" counterparts during the region's dry season. Details of the findings will be presented today at the American Geophysical Union's 2008 Joint Assembly in Fort Lauderdale, Fla.

Discovery of the link between rain and pollution was possible due to near-simultaneous measurements from multiple satellites making up the string of satellites in the Afternoon Constellation, more commonly called the A-Train. "Typically, it is very hard to get a sense of how important the effect of pollution on clouds is," said Anne Douglass, deputy project scientist at Goddard for NASAs Aura satellite. "With the A-Train, we can see the clouds every day and we're getting confirmation on a global scale that we have an issue here."

Jiang's team used the Microwave Limb Sounder on
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