August 6, 2006

Balloons Work with Satellite to Gauge Bad Air Days

By Deborah Zabarenko

BELTSVILLE, Maryland -- The weather outside was frightful: hot, humid and layered with a haze of pollution so thick it seemed it could be cut with a machete -- a perfect day to use balloons and a satellite to monitor some bad air.

On the last full day of a monthlong heat wave, when most sensible people might prefer to be sitting in the shade with a cool drink, climate scientists were out in a sunny field, coordinating the launch of a weather balloon with a satellite called Aura that zoomed some 400 miles above.

"If Aura is up there trying to assess air quality, give us hot, polluted, hazy summertime in the Washington area and see how it does," NASA scientist David Whiteman said on Thursday, when temperatures in nearby Washington topped 100 degrees (37.8 C).

The balloon-satellite linkup took place at the Howard University Center for Atmospheric Science, a bucolic compound between the U.S. capital and Baltimore, not coincidentally in the middle of a heavily populated corridor along the U.S. East Coast that typically has some of the worst air pollution in the country.

"A research site of this quality and scope is typically not in this kind of environment," said Whiteman, who is based at NASA's Goddard Space Flight Center.

"It's placed in a more pristine area where it's easier to understand the atmosphere," he said. "Well, it's also important to try and understand the atmosphere where people live and where things get messy and polluted."

To do that, Whiteman and other scientists had to time the balloon launch of a cluster of weather instruments with Aura's pass overhead. So while Aura looked down from its polar orbit to make measurements of such greenhouse gases as methane, ozone and water vapor, the instruments rising on the tail of a big helium balloon took measurements at the same time.


Water vapor may seem harmless enough, but it is actually a powerful and abundant greenhouse gas. The higher the concentration of water vapor in the atmosphere, the more heat the atmosphere can hold. Greenhouse gases, including water vapor, contribute to global warming, trapping heat near Earth's surface like the glass walls of a greenhouse.

Data started streaming down from the balloon instruments immediately after launch, and researchers from NASA, the National Oceanic and Atmospheric Administration and Howard University watched the information on computer screens in mobile offices at the side of the field.

They were watching to see if the balloon data gibed with the information from Aura; ultimately, they want to use Aura and other satellites to predict air quality, but they need to check its data against proven sources, like the instruments on the weather balloon.

"This is a new thing to try and make these measurements from space and to try and do air quality forecasting," Whiteman said in an interview. "So we need to use more standard measurement techniques ... such as things we do from the ground, and compare those with the satellite and assess how well the satellite is performing."

Aura is meant to help figure out how Earth's climate is changing, but the phenomenon of human-caused global warming is not in doubt, according to a NASA fact sheet describing the satellite's mission.

"It is undeniable that human activity is beginning to alter the climate," the fact sheet reads. "The global rise in surface temperatures since the 1950s is correlated with the increase in greenhouse gases, especially carbon dioxide."