Weather Balloons
Twice a day, every day of the year, weather balloons are
released simultaneously from almost 900 locations worldwide! This
includes 92 released by the National Weather Service in the US and its
territories. The balloon flights last for around 2 hours, can drift
as far as 125 miles away, and rise up to over 100,000 ft. (about 20 miles)
in the
atmosphere!
Weather balloons, which are made of latex or
synthetic rubber (neoprene), are filled with either hydrogen or
helium. The sides are about 0.051 mm thick before release
and will be only 0.0025 mm thick at typical bursting
altitudes! The balloons, which start out measuring about 6 ft. wide
before release, expand as they rise to about 20 ft. in diameter! An
instrument called a radiosonde is attached to the balloon to measure
pressure, temperature and relative humidity as it ascends up into the atmosphere. These instruments
will often endure temperatures as cold as -139°F (-95°C), relative humidities from 0% to 100%, air pressures
only a few thousandths of what is found on the Earth's surface, ice, rain,
thunderstorms, and wind speeds of almost 200 mph! A transmitter on the radiosonde sends the data
back to
tracking equipment on the ground every one to two seconds. By tracking the position of
the radiosonde, we can also calculate wind speed and wind direction.
The radiosonde is powered by a small battery.
 During nighttime releases, a lightstick is attached so the
balloon can be tracked by meteorologists until the tracking equipment
locks onto the radio signal. A parachute, attached to the end of the
balloon, allows the radiosonde to fall slowly to the ground at speeds less
than 22 mph after the balloon bursts. Each radiosonde contains a
mailing bag and instructions on what to do if you find one. About
20% of the 75,000 radiosondes sent up each year in the US are found and
returned. These instruments are fixed and reused, saving the
government money.
Weather balloons are the primary source of data
above the ground. They provide valuable input for computer forecast
models, local data for meteorologists to make forecasts and predict
storms, and data for research. Computer forecast models which use
weather balloon data are used by all forecasters worldwide, from National
Weather Service meteorologists to your local TV weatherman! Without
this information, accurate forecasts beyond a few hours would be almost
impossible!
Videos of Weather Balloons:
Weather
Balloons: Watch a video about weather balloons and learn how the
data we collect is used! (You will need a RealVideo plug-in)
Weather
Balloon Release: Watch a weather balloon being inflated and
released! Download too slow? How about trying a smaller file
of the release. (You will need a RealVideo plug-in)
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www.weather.gov
