Taking measurements of the atmosphere is quite important and all measurements cannot be taken by satellite and radar. For this reason, a weather balloon or a “sounding balloon” is sent up in the atmosphere to take measurements. These balloons are launched with instruments aboard to send back information on atmospheric pressure, temperature, humidity and wind speed. The device that measures this information is called a radiosonde. These balloons can be tracked by radar and GPS, thus obtaining wind data. They can also stay at a constant altitude for long periods of time. This information is transmitted back to earth to surface observers.
The balloon itself usually produces the lift itself and is made of highly flexible material. The radiosonde hangs from a string at the base of the balloon. The balloon itself is filled with hydrogen, although it can be filled with helium. The ascent rate can be controlled by the amount of gas in the balloon and can reach heights of 25 miles or more.
These balloons are launched all over the world from every weather forecasting office, (800 worldwide and122 in the United States alone). The information from these balloons is input into computer models and aid in forecasting. These balloons are launched twice a day, at Midnight and Noon (Greenwich Mean Time). Some facilities will do occasional supplementary special releases when meteorologists determine there is a need for additional data between the 12 hour periods. Our own Candice Boling has also launched weather balloons at her prior position, you can see her picture below.
Military and civilian government meteorological agencies such as the National Weather Service here in the U.S. launch balloons, and by international agreements almost all the data are shared with all nations. As hundreds of weather balloons go up simultaneously across the globe twice a day, meteorologists anxiously await the information, which is then fed to weather models, which in turn is turned into an official forecast. Without weather balloons, it would be quite difficult to get an accurate gauge on the atmospheric conditions.