Weather balloon
A weather balloon, also known as a sounding balloon, is a balloon (specifically a type of high-altitude balloon) that carries instruments to the stratosphere to send back information on atmospheric pressure, temperature, humidity and wind speed 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, GPS). Balloons meant to stay at a constant altitude for long periods of time are known as transosondes. Weather balloons that do not carry an instrument pack are used to determine upper-level winds and the height of cloud layers. For such balloons, a theodolite or total station is used to track the balloon's azimuth and elevation, which are then converted to estimated wind speed and direction and/or cloud height, as applicable.
"Sounding balloon" redirects here. Not to be confused with observation balloon. This article is about atmospheric and meteorological sounding balloons. For balloon space probes, see List of Solar System probes.Weather balloons are launched around the world for observations used to diagnose current conditions as well as by human forecasters and computer models for weather forecasting. Between 900 and 1,300 locations around the globe do routine releases, two or four times daily.[1][2][3][4]
History[edit]
One of the first people to use weather balloons was Léon Teisserenc de Bort, the French meteorologist. Starting in 1896 he launched hundreds of weather balloons from his observatory in Trappes, France. These experiments led to his discovery of the tropopause and stratosphere.[5] Transosondes, weather balloons with instrumentation meant to stay at a constant altitude for long periods of time to help diagnose radioactive debris from atomic fallout, were experimented with in 1958.[6] The drone technology boom has led to the development of weather drones since the late 1990s.[7] These may begin to replace balloons as a more specific means for carrying radiosondes.[8]
Materials and equipment[edit]
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.
The balloon is usually filled with hydrogen, though helium - a more expensive, but viable option nonetheless - is also frequently used. The ascent rate can be controlled by the amount of gas with which the balloon is filled. Weather balloons may reach altitudes of 40 km (25 mi) or more, limited by diminishing pressures causing the balloon to expand to such a degree (typically by a 100:1 factor) that it disintegrates. In this instance the instrument package is usually lost,[9] although a parachute may be employed to help in allowing retrieval of the instrument. Above that altitude sounding rockets are used to carry instruments aloft, and for even higher altitudes satellites are used.