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Up and away for forecast

By CURTIS KRUEGER
Published November 25, 2006

RUSKIN - Colleen Rhea runs outside a small concrete building in the night, clutching a contraption that looks like a science fair project.

It's a 6-foot hydrogen-filled balloon, with a string attached to a flimsy-looking orange plastic parachute, a glowing yellow light and a few electronic instruments encased in Styrofoam.

She lets go, and the balloon spirals from her fingers into the purple sky, where it will soar 20 miles above Earth, expand to more than twice its size, acquire a coating of ice and ultimately say whether this is a good weekend for the beach.

Twice a day at 92 locations around the country, the National Weather Service launches weather balloons like this one. It's a 60-year-old ritual that forms a backbone of weather forecasting across the United States.

"Weather forecasting of any value would be just about impossible without weather balloons or a suitable replacement," said Richard Mamrosh, a meteorologist with the weather service in Green Bay, Wis.

Mamrosh is among those who say the time for a suitable replacement is almost here.

Mamrosh has spent years studying whether airplanes could regularly record the same kind of data balloons provide. Since airplanes fly frequently, its possible they could provide more and better data, he said, meaning better weather forecasts.

Weather balloons are important because the basics of forecasting - temperature, air pressure, humidity, wind speed - differ depending on elevations. Meteorologists want to know what's happening in the air above us because it helps them understand the weather systems that will soon be making us wet, hot or cold.

The balloon that Rhea let go of earlier this month carried devices to measure temperature, humidity and atmospheric pressure. And by radio tracking the balloon's location, computers calculated wind speed.

Rhea said the Ruskin weather service office is getting ready to attach GPS devices to the twice-daily balloon launches, which should make the data more precise.

Mamrosh thinks airplane-based instruments, also backed up by GPS, could prove even better. Hundreds of airplanes transmitting data from myriad locations almost continuously would certainly improve forecasts.

The weather balloons program, he said, "is really the only observation system that has not changed much since World War II."

Another drawback to the balloon system is waste. All those icy balloons eventually burst and fall back to Earth. Some balloons are found and returned to the weather service, but most aren't. Each launch costs about $300.

"If you could save, say $600 a day from not launching balloons ... that's about $180,000 that would be freed up" for another system.

Mamrosh said airplanes already record some climate data, but often not humidity, so they would need to be fitted with additional sensors.

Still, balloons have some advantages. Commercial airplanes don't fly nearly as high as the weather balloons. And airplanes don't fly frequently from some of the remote sites where weather balloons are regularly launched. Also, the balloons are launched at the same time every day, which aids in forecasts.

"I don't think there's any meteorologist who would say we don't need weather balloons anymore," said Dr. Jon E. Ahlquist, associate professor of meteorology at Florida State University. But he said airplanes can and already do provide additional data to supplement what the balloons provide.

Mamrosh said there needs to be additional study and testing of the airplane plan.

Among questions to be answered: What would happen in severe storms or when airplanes are grounded, such as after an event like the 9/11 terrorist attacks?

Balloon ride

What's on the balloon? A string on the balloon is attached to a small instrument package called a radiosonde. The radiosonde is a little larger than a can of soda, and consists of special sensors that measure humidity, temperature, pressure, wind speed and wind direction.

If you find one: The radiosonde is harmless and safe to handle. You may detect an odor coming from the instrument, but this is from a sulfur compound used in the battery. Each radiosonde comes with a mail bag (postage is pre-paid) and mailing instructions.

Rate of return: The NWS network releases about 75,000 radiosondes each year, but only about 20 percent are returned to the NWS for reconditioning.

SOURCE: NOAA

[Last modified November 25, 2006, 00:07:13]