Weather balloon

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A hydrogen filled balloon at Cambridge Bay Upper Air station, Nunavut, Canada

Close up of a hydrogen filled balloon at Cambridge Bay Upper Air station, Nunavut, Canada

Rawinsonde weather balloon just after launch. Notice a parachute in the center of the string and a small instrument box at the end. After release it measures many parameters. These include temperature, relative humidity, pressure, and wind speed and wind direction. This information is transmitted back to surface observers.

A weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, and humidity by means of a small, expendable measuring device called a radiosonde. To obtain wind data, they can be tracked by radar, radio direction finding, or navigation systems (such as the satellite based Global Positioning System).

The balloon itself produces the lift, and is usually made of a highly flexible latex material (though Chloroprene may also be used). The unit that performs the actual measurements and radio transmissions hangs at the lower end of the string, and is called a radiosonde. Specialized radiosondes are used for measuring particular parameters, such as determining the ozone concentration.

In North America prior to release the balloon is usually filled with hydrogen (though helium can be used as a substitute) gas. The ascent rate can be controlled by the amount of gas the balloon is filled with. Weather balloons may reach altitudes of 40 km (25 miles) or more, limited by diminishing pressures causing the balloon to expand to such a degree (typically by a 100:1 factor) that it disintegrates. The instrument package is usually lost. Above that altitude sounding rockets may be used. After sounding rockets, satellites are used for even higher altitudes.

Major manufacturers of balloons are Totex Corporation and Cosmopren of Japan and Kaysam (now Kaymont) of the U.S..

Weather balloons are sometimes cited as the cause for UFO sightings, e.g. Project Mogul.

[edit] See also

• High altitude balloon
• Rawinsonde

[edit] External links

Wikimedia Commons has media related to:

Weather balloon

• Atmospheric Soundings for Canada and the United States - University of Wyoming
• Balloon Lift With Lighter Than Air Gases - University of Hawaii
• Examples of Launches of Instrumented Balloons in Storms - NSSL
• Federal Meteorological Handbook No. 3 - Rawinsonde and Pibal Observations
• Kites and Balloons - NOAA Photo Library
• NASA Balloon Program Office - Wallops Flight Facility, Virginia
• National Science Digital Library: Weather Balloons - Lesson plan for middle school
• Pilot Balloon Observation Theodolites - Martin Brenner, CSULB