Early launch of radiosonde developed by the U.S. Bureau of Standards at Washington,
D.C. Airport blimp hangar (May 7, 1936).
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A radiosonde is a small box-like instrument that is carried into the upper
atmosphere by balloon. As it travels upward, it transmits meteorological measurements
to ground stations. Radiosondes measure temperature with a thermometer, humidity
with a hygrometer, and air pressure with a barometer. Radiosondes are attached
to helium-filled neoprene balloons that are designed to burst when they reach
a specified altitude. They can operate up to around 100,000 feet (30,000 meters).
Radiosondes began to be used by investigators during the 1920s and 1930s and
were in common use by the late 1930s. Their advantage over other types of meteorological
instruments is that they do not have to be returned to Earth for their data
to be retrieved.
Meteorologists send these instruments up into the upper atmosphere on balloons
twice a day simultaneously around the world--at midnight and at noon Greenwich
Mean Time (GMT) Radiosondes take continuous measurements as the balloon rises
through the air. This information is transmitted by radio back to the ground.
Special tracking equipment monitors the movement of the radiosonde, which is
converted into wind speed and wind direction data. When the balloon bursts,
the radiosonde falls back to Earth by parachute.