Tomorrow's forecast: more precise, maybe

Device: A satellite launched this month contains a sensor that scientists hope will aid meteorologists.

May 26, 2002|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Bad weather is bad enough.

But bad weather that comes as a surprise costs money, makes people angry and embarrasses forecasters. The same is true for predicted storms that veer away after everyone has boarded up their windows and fled to higher ground.

Soon, with help from a $70 million set of infrared detectors designed by a physicist at the University of Maryland, Baltimore County, a new satellite may give meteorologists a way to reduce the frequency of these costly forecast "busts."

"That's what the public really, really hates," said UMBC's L. Larrabee Strow. "It's really the big screwups they want to fix. Who cares if it's partly cloudy instead of sunny?"

NASA's Aqua satellite, launched May 4 from California, circles the globe once every 24 hours, in a polar orbit 437 miles high. Its five- to seven-year mission: to provide forecasters and researchers with data on how water cycles through the atmosphere, the land and the oceans. From that, scientists hope to gain insight into weather and global climate change.

It's primarily a research tool. But officials at the National Aeronautics and Space Administration hope that within a year, Aqua's data will begin to improve the accuracy of forecast models used by the National Weather Service.

Aqua is 21 feet long, weighs more than three tons and cost $1.3 billion. It is the second of three big satellites that will form the core of NASA's expanding Earth Observing System for environmental research.

Strow's piece of the action is a set of infrared detectors in one of Aqua's six instruments.

The mercury cadmium telluride detector array is no bigger than a hockey puck. But it took Strow and a team of scientists from NASA and four universities 12 years to develop the technology and build the sensors, which are part of a $238 million device called AIRS (Atmospheric Infrared Sounder).

AIRS' task will be to peer through the atmosphere as Aqua circles the globe. By measuring infrared radiation at different wavelengths, AIRS can remotely sense the temperature, humidity and cloud characteristics of discreet 1-kilometer "slabs" of air, from the surface to about 12 miles up.

Such input of real measurements is needed regularly to keep the National Weather Service's computer forecasting programs in touch with reality. Without real data, Strow said, "it wanders into nonsense."

Today, the best data comes from balloon-borne instruments called "radiosondes." They're lofted 10 miles into the sky twice a day from sites on land - most in developed nations. In poorer parts of the world, and over the oceans, meteorologists must rely on satellites whose technology hasn't changed since 1978.

Strow's intricate detectors will send a torrent of data - the equivalent of 30,000 novels a day. It should provide more accurate readings, and a more detailed global picture of what's happening in the atmosphere.

The goal is to produce five- to seven-day forecasts as accurate as today's three- to five-day forecasts. "It's an experiment," Strow says, "but we have strong reason to believe it will [work]."

Better weather forecasts are important, but Strow's personal interests are in using AIRS to improve our understanding of long-term global climate change, and to better predict where it is taking us.

He thinks AIRS will provide insight into how the Earth distributes heat from the tropics to the temperate latitudes, and how it sheds heat from the upper atmosphere into space.

His detectors will also gather global data on carbon dioxide and methane - with water vapor, the most potent of the greenhouse gases that influence global warming.

"This instrument is our only chance for a global measurement of carbon dioxide," Strow said. In the long term, it may help scientists solve the mystery of the carbon dioxide "budget" - where it's produced, how much of it is absorbed into the environment, and where.

"We can measure carbon dioxide better than anything globally," he said. "Whether that will be enough ... we don't know."

Strow, 49, is a Marylander, born and bred. He and his wife live in Elkridge - just a mile from where he grew up.

He graduated from UMBC in 1974 with a bachelor's degree in physics, and received his doctorate from the University of Maryland, College Park in 1981. He worked for NASA at the Goddard Space Flight Center in Greenbelt for 10 years before returning to UMBC in 1984 to teach and do climate research.

NASA has invested $3.4 million in AIRS research at UMBC led by Strow and colleagues Wallace McMillan and Ray Hoff.

"In terms of the size of the program, I don't think there's anything comparable" at the school, Strow said. It involves 15 researchers at UMBC and four or five more at the school's Joint Center for Earth Systems Technology, a cooperative teaching and research agreement with Goddard Space Flight Center.

Firing up his computer, Strow shows video of Aqua's pre-dawn launch - which he attended - as proudly as a new father displays baby pictures.

"When you've got 12 years of your life in something, it's both exciting and intimidating," he said.

Now that AIRS is in orbit, and healthy, Strow and his team will spend long hours in the coming months getting its complex hardware and heavy-duty computing systems under control.

"NASA headquarters said, `We want good data within one year,'" Strow said. "We all consider that a very tight schedule."

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