radiosonde

Radiosonde is a battery-powered instrument package carried aloft by a weather balloon to measure and transmit atmospheric data during ascent into the upper troposphere and lower stratosphere. The payload includes sensors for air pressure (to derive altitude), temperature, and relative humidity, along with a radio transmitter, telemetry electronics, and a microcontroller. Many radiosondes also include a GPS receiver to determine position and wind speed and direction by triangulating movement; others estimate wind using tracked radio signals. Data are transmitted continuously to ground receive stations, typically from launch sites to high-altitude receivers as the balloon rises.

The balloon bursts at altitude, and the radiosonde payload descends by parachute, either recovered or left to descend for retrieval in some cases. Ascents usually reach 20–35 km, depending on balloon size and atmospheric conditions.

Ground-based meteorological networks collect the transmitted data, quality-control it, and publish vertical profiles of temperature, humidity, pressure, and wind. These radiosonde soundings provide critical input for numerical weather prediction models and climate research, and are used to monitor atmospheric stability and to calibrate satellite observations.

Development began in the early 20th century and became widespread after World War II; today thousands of radiosondes are launched globally each day from meteorological agencies and research institutions.