Facts About Weather Balloons


* Of 91 civilian and military stations in the lower 48 states which take upper air observations by releasing weather balloons, Aberdeen is one of 66 stations which routinely take observations twice a day.

* Weather balloons are released daily from as far north as Alert, Northwest Territories (Canada) and from as far south as the South Pole. There are 870 land-based upper air stations in more than 150 countries, with 22 upper-air stations on-board special ships.

* As of September 1997, 656 upper air offices worldwide release weather balloons when it is Midnight and when it is Noon in London, England. The remaining upper air stations release balloons as-needed to support special research projects or military operations-a few stations only release one balloon per day.

* An instrument (called a radiosonde) attached to the balloon measures the atmospheric pressure, air temperature and relative humidity. Wind speed and direction are calculated by tracking the instrument with a high-gain antenna (similar to a satellite-TV dish).

* The balloon rises an average of 1000 feet per minute. It typically bursts around 100,000 ft above ground--where the atmospheric pressure is one percent the pressure at sea-level.

* Rapid City has been releasing weather balloons since October 6, 1943.

* Huron was an upper air station from May 16, 1954 through the morning of November 17, 1994. After moving the equipment during the day, observations began that evening from Aberdeen.

* The closest upper air stations to Aberdeen are Bismarck, Minneapolis, Rapid City, Omaha, Shilo (Manitoba) and North Platte.

* The evening upper air observation on May 31, 1996 began just 17 minutes after a tornado skipped-by the Aberdeen regional airport along Highway 12. Since there are very few observations taken so close to a tornado, researchers are studying the data collected by our office for clues about the atmospheric conditions which produce tornadoes.

* There were only two times during the winter of 1996/97 when we could not take an upper air observation because of blizzards. In both cases, turbulence from high winds popped the balloon near the ground.

* A weather balloon released on a summer afternoon may experience a temperature drop of more than 170 degrees Fahrenheit in less than an hour. Balloons are made from a special rubber which is designed to tolerate the extreme temperature changes.

* A weather balloon released from Bismarck was found a few miles northeast of Victor SD the winter of 1997.

* In December 1996, an Aberdeen balloon measured a wind speed of 230 miles an hour at 30,000 ft. Winds aloft may have been even stronger, but the balloon was pushed so far away that we could not continue making accurate calculations of wind speed.

* Nearly all upper air stations in the United States use hydrogen gas to inflate the balloons.

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