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It's a bird,it's a plane: National Weather Service launches daily weather balloon

Bellemont National Weather Service meteorologist Michael Langevin prepares to launch a weather balloon June 18.  Ryan Williams/WGCN

Bellemont National Weather Service meteorologist Michael Langevin prepares to launch a weather balloon June 18. Ryan Williams/WGCN

WILLIAMS, Ariz. - Look south of I-40 at 4 p.m. and you might see a big, white balloon shoot up into the sky.

Twice a day, the National Weather Service (NWS) office in Bellemont sends a five-foot in diameter balloon with a small, suspended radiosonde (German for radio-sounding) skyward to gather weather data. Bellemont is one of 92 offices nationwide that use weather balloons daily.

As the helium or hydrogen balloon with the radiosonde rises through the atmosphere the sensors measure air pressure, temperature and relative humidity.

These sensors are linked to a battery powered radio transmitter that sends the data every second to a sensitive ground tracking antenna on a specific radio frequency. These radio signals are converted to meteorological values, put into a special code form and then recorded by computers.

Satellites, aircraft and ground sensors use remote sensing to collect atmospheric data, but the weather service has found they still need radiosonde observations. No other system can match the vertical resolution and altitude coverage, so they remain essential to modern meteorology.

"Radiosondes are the most efficient and least expensive method to get an actual instrument up into the atmosphere," said Brian Klimowski the meteorologist in charge of the National Weather Service in Bellemont, "We're able to get measurements from the ground level up to 100,000 feet."

The radiosonde rises at about 1,000 feet per minute through the atmosphere until it reaches the stratosphere, which takes approximately one and a half to two-hours. The balloon expands as it rises and when it reaches 100,000 feet the decrease in air pressure allows the balloon to expand to a diameter of around 20 to 25 feet.

The air pressure, along with the extremely cold temperatures (-90 degrees), cause the balloon to burst at the high altitude and the radiosonde transmitter descends by parachute back to the ground. Only about 20 percent of the radiosondes are recovered.

"About once a month we have someone walk into the weather station and hand us one," Klimowski said.

The Weather Service has used radiosondes since the late 1930s to measure upper air conditions. Technological improvements have been made throughout the years and NWS recently upgraded to GPS Sondes. Radiosondes provide a primary source of upper-air data. Meteorologists use the data in a variety of applications including storm, aviation, fire weather and marine forecasts, weather prediction models, weather and climate research, air pollution models, and ground truth for satellite data.

"We have remote sensing from satellites that can do a pretty good job of getting a large scale temperature profile for us and some estimates of relative humidity throughout the atmosphere," Klimowski said. "But it doesn't do a very good job on the surface and that's where the action is. So we still need radiosondes and the balloon launch program so we can get the high resolution data in the lower atmosphere."

There are 92 radiosonde launching stations across the United States, and more than 800 worldwide.

"What's really cool is that they all launch at the same time," Klimowski said, "As our balloon is rising, over 800 others are rising at the exact same time across the world. This is important because we can get a snapshot of the atmosphere at that exact time. We can initialize the numerical forecast models from those data and also do analyses of our local flight as well."

Data collected by radiosonde in summer is particulary important for thunderstorm forecasting.

"You can tell a lot about the stability of the atmosphere and how conducive that might be for thunderstorm development," Klimowski said.

The NWS in Bellemont has 14 meteorologists who assist with weather forecasting. All the meteorologists are certified to launch balloons, although two hydro meteorological technicians launch most of the balloons. Balloon launches occur at 4 a.m. and 4 p.m. every day.


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