What is a Radiosonde?

Worldwide, nearly 900 upper air stations, mostly in the Northern hemisphere, gather information about our atmosphere.  At precisely 0000 and/or 1200 UTC, 365 days a year, these observations are made using radiosondes.

This small instrument package is suspended below a 6 foot wide balloon filled with hydrogen or helium. As this instrument is lifted up into the sky, sensors measure pressure, temperature, and relative humidity and a battery powered transmitter sends the readings to a ground receiver. Click on the link at the end of this article to see a video of a weather balloon and radiosonde release.

Obtaining accurate data aloft is essential to predicting changes in the atmosphere and this powerful little package is our primary source for this critical data.

By tracking the ascent of the radiosonde, information on wind speed and direction  aloft can also be determined. These observations are called "rawinsonde" observations. There is a minimum height to which the instrument must be lifted before the data can be utilized.

A radiosonde is equipped for quite a trip and can ascend to over 115,000 feet and drift more than 125 miles from the release point.  Flights can last over two hours and the instrument can be exposed to extremely low temperature and air pressure. 

As the balloon rises, it expands in the decreasing pressure until it finally reaches its limit and bursts. At this point, the radiosonde falls back to the ground, drifting back to earth attached to a small parachute.  When someone finds a radiosonde they can return it to the NWS for reconditioning.  Mailing instructions are printed on the side of the radiosonde and the finder can return it at no cost.

According to the National Weather Service, Data applications include:

• Input for computer-based weather prediction models
• Local severe storm, aviation, and marine forecasts
• Weather and climate change research
• Input for air pollution models
• Ground truth for satellite data

Click here to view: Weather Balloon and Radiosonde Release Video

The above article is based on information from NWS  http://www.erh.noaa.gov/er/gyx/weather_balloons.htm

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