Weather balloons are launched from the upper air site at the
Salem airport. They are filled with helium inside of the small building, the
taken outside to launch. The helium, which is a very light gas, allows the balloon
to reach heights of 30,000 to 50,000 feet above the earth's surface in a few
minutes. As the balloon rises, it will eventually break due to change in atmospheric
pressure. As the balloon rises through the air, a transmitter, called radiosonde,
sends temperature, relative humidity, wind and pressure data back to the operator
in the small building. The technician insures the data is accurate before sending
into the computer system to be used in computer modeling and forecasts.
The balloons are launched twice every day from locations around the world all
at the same time! Why? Because by launching at the same time, meteorologists
can get a nearly instant snapshot of the earth's atmosphere. For most locations,
these times also reflect the atmosphere at its two extremes: the most calm (around
sunrise) and most excited or active (late afternoon).
But what happens to the radiosonde when the balloon breaks? The radiosonde is
protected by a styrofoam container, which cushions the radiosonde upon impact
with the ground. However, a small parachute will usually pop out as the radiosonde
falls, slowing its descent. It is not uncommon to find the small boxes with
an orange parachute some 100 miles away from its launching station. In our area,
the launch site is Salem. Balloon remains have been found around Mount Hood,
Sisters, Warm Springs, Portland and Hood River.
Are the radiosondes returned? Frequently, the radiosondes are discovered in
a pasture, grove of trees, creek, backyards and other locations. A self-addressed
postage-paid envelope, which is in a compartment of the radiosonde container,
can be used to return the radiosonde to a reconditioning center for repair,
and eventual reuse.
NOAA's National Weather Service
5241 NE 122nd Avenue
Portland, OR 97230
Phone: 503.326.2340
Weather Line: 503.261-9246, -9247
www.weather.gov 
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