upper-air sounding

Technique used to measure the pressure, temperature and humidity of air as well as wind speed and wind direction at various altitudes.

sounding balloon

Pressurized balloon equipped with measurement instruments used to collect atmospheric data (up to an altitude of 20 mi), which it then transmits to the ground by radio signal.

radiosonde

Instrument composed of sensors that measure the pressure, temperature and humidity of air; it then relays the data to ground level using a radio transmitter.