How Do Weather Balloons Work?

Learn about how this simple instrument collects important high-tech data on what's happening in the atmosphere.

With all the detailed weather forecasts that are reported to us every day, and the sophisticated equipment with which it’s captured (i.e., Doppler radar, computer models, sky cams and the like), it almost seems implausible that we often rely on data gathered by a simple helium balloon released into the sky.

However, the weather balloon is in fact a very modern-day, scientific instrument used to collect some very important information on what’s happening in the atmosphere. Weather observatories all over the globe launch thousands of weather balloons daily. In the United States alone, weather balloons are launched twice a day from over 100 weather stations, which equals to over 73,000 balloons sent skyward every year.

The balloons, which are usually made of latex or neoprene, are filled with hydrogen or helium, and released into the air. As the balloon climbs into the atmosphere, it collects data and sends it back via a radiosonde, a lightweight cardboard box filled with scientific instruments, that’s tied to the bottom of the balloon. An antenna on the radiosonde allows transmission of information back to a weather lab, and a team on the ground inputs the raw data into a computer, which feeds into another real-time system that meteorologists can access to prepare forecasts at both the local and national levels.

As the balloon increases in altitude, the pressure increases and it grows from the size of a large yoga ball to the size of a bus. When the balloon reaches a certain altitude — often elevations of 20 miles or higher — it bursts, sending the radiosonde back to Earth by way of a mini parachute. The parachute slows the device’s descent, and it’s usually many hours and hundreds of miles from where it first lifted off that the weather balloon (or what’s left of it) finally touches the ground.

If you ever stumble upon one of these radiosondes, don’t be alarmed. The device is marked with instructions to return it to the National Weather Service for refurbishing, but less than 20 percent are sent back.

A century ago, scientists could only predict the weather from measurements taken on the ground. Later, they relied on military airplanes outfitted with devices to collect the data. But cabins weren’t adequately pressurized back then so pilots had elevation limitations, making this method obsolete. Kites were also used, with data-capturing devices attached, but reaching high elevations from which to launch them proved dangerous for meteorologists. With weather balloons scientists have married the old (balloons) with the new (high-tech radiosondes) to help determine weather conditions days in advance. Whether it’s a tornado warning or the weather report on the 6 o’clock news, weather balloons are what keep people on the ground tuned in to the meteorological workings of the upper atmosphere.  High-altitude weather data is critical for predicting oncoming significant weather events like tornadoes, thunderstorms or flash floods. Thanks to weather balloons, officials can prepare for a weather disaster hours before it strikes.

Weather balloons collect and send the following critical data back to the ground: wind speed, wind direction, air pressure, air temperature, relative humidity, cloud type, and GPS location. This information is used for such research projects as local severe storm, aviation, and marine forecasts, weather and climate change research, and studies on air pollution.

According to the National Oceanic and Atmospheric Administration, each balloon launch costs $200. This includes the price of the balloon, hydrogen and radiosonde.

Since the 1930s the National Weather Service has used weather balloons with radiosondes. So even though it’s been more than 70 years since scientists sent up the first experimental weather balloon, they remain the workhorses of modern meteorological forecasting.

Take a look at this video of a weather balloon launch:

 Photo courtesy of

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