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Sippican 2
Tue Sep 21, 2004
Listen in RealAudio 
Hi, I’m Bryan Yeaton, and this is The Weather Notebook. Yesterday, we spoke with
Tom Curran of Massachusetts-based Sippican, Incorporated about the instrument
package that trails 70 feet beneath a weather balloon: the radiosonde. Today, we find
out what these little packages can do.
Curran: The radiosonde has several sensors which are exposed before the balloon –
it’s attached to the balloon and launched. You have a temperature sensor which is
extended from the instrument which gives you a measurement of the temperature in
the atmosphere every one second; you have a relative humidity sensor and, again,
providing the same one-second measurements of the moisture content of the
atmosphere. Certain types of radiosondes also provide pressure measurement.
What’s this yellow thingy sticking out of the top?
Curran: This is a GPS antenna. So on a GPS configuration you need to be able to
receive the signals from the GPS satellites around the earth and determine the
position of the measurement.
So it gets a lot more accurate?
Curran: Extremely accurate. It really becomes important when you realize how far the
balloon travels. In the northeast U.S. in the wintertime, it’s not uncommon for the
radiosonde to be 120 miles away from the station when the balloon bursts at 100,000
feet.
Curran says the balloon is about eight feet across at launch. But it doesn’t stay that
small.
Curran: As it rises in the atmosphere, the balloon continues to expand. So that balloon
that’s eight feet in diameter on the ground will be somewhere between 20 feet and 24
feet in diameter when it bursts at 100,000 feet.
Sippican is a radiosonde supplier for the National Weather Service, which launches
about 75,000 of these a year. The Weather Notebook is funded by Subaru of America
and the National Science Foundation.
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