What is a Radiosonde?

Radiosondes are atmospheric sensors that provide an accurate, high-resolution description of the Earth’s atmosphere from the ground to 100,000 ft.  Radiosondes are carried into the air by latex weather balloons filled with helium or hydrogen.  Radiosondes measure atmospheric pressure, air temperature, water vapor (humidity) and winds (speed and direction).  Modern radiosondes contain a GPS receiver to calculate wind speed and direction, and a radio transmitter to send the data back to the ground.  Since they were first developed in the 1930s, radiosondes have become smaller, lighter, more accurate and less expensive.

The most common use of radiosondes is for synoptic soundings, which are released once or twice a day (at 00Z and 12Z) from fixed locations around the globe.  These soundings are carried out simultaneously by national weather services around the world to create a three-dimensional picture of the Earth’s atmosphere at one point in time.  Data from approximately 600 sites is transmitted to data centers for use in numerical weather prediction (NWP) models maintained by major governments and research institutions.  These models produce the two to seven-day weather forecasts that everyone relies on for daily activities.

The first thing to understand about weather forecast models is that you need data from many points on the globe. Some NWP models only simulate a region of the atmosphere, but global models (GFS, ECMWF) provide the boundary conditions for these regional models. As winds circle the globe, the weather you experienced today will become someone else’s tomorrow.  Radiosondes are the backbone of NWP models, but vast amounts of data from other sources, such as surface stations, radars, and satellites, also are used to predict the weather.     

Radiosondes are also used by universities and research institutions for many different purposes. Some study how the atmosphere changes over time (climatology), others research the dynamics of severe thunderstorms, while some attach Ozone sensors to radiosondes to study stratospheric Ozone.  Radiosondes also are used by militaries, who use the meteorological data for various purposes such as aviation forecasts and parachute drops. A Skew-T diagram, as shown below, is used often used by meteorologists to visualize the radiosonde data and make short-term predictions of the weather. This Skew-T image is created using a product known as SHARPpy (https://github.com/sharppy/SHARPpy), which is an open-source program that is used to visualize radiosonde data. The data in the image is from a radiosonde that was launched at InterMet in Grand Rapids, MI.

Radiosondes and weather balloons are not dangerous to airplanes or birds.  As the balloons rise into the atmosphere they expand and eventually burst.  The radiosonde falls back to the ground using a small parachute to slow the descent.  If you find a radiosonde on the ground, you can dispose of it without any special precautions.  Modern radiosondes contain no lead or hazardous substances. They are designed for a single-use.

If you are curious about where they sonde came from, please send us an e-mail with the serial number and we might be able to help identify it.          

Atmospheric soundings are a complex exercise that requires a ground receiving system, specialized software and the equipment needed to inflate and release a weather balloon.  Radiosondes are not suitable for individuals and are usually flown by universities, research institutions or government agencies.  InterMet offers a wide range of sounding systems for portable field use, synoptic observations, and military applications.  Our latest radiosonde model, the iMet-4 can be supplied in different formats depending on the mission objectives.  InterMet also supplies atmospheric sensors for use on fixed and rotary-wing UAVs.