Radiosondes--weather balloons with instrument packages attached--have been a mainstay of atmospheric observing since the 1930s. The instruments measure temperature, pressure, and humidity at frequent intervals as they rise, and the readings are sent via radio to a control center. The location of the instrument package can be monitored by the Global Positioning System, which enables the wind speed and direction at each height to be inferred. A mobile sounding system at the National Center for Atmospheric Research allows radiosondes to be launched for research from remote locations. Pictured: Atmospheric scientist Ned Chamberlain
