The weather balloon is larger than your typical party balloon. It’s about 6 feet wide when it’s inflated. It gets blown up with helium or nitrogen. Attached with a string is a weather instrument called a radiosonde which makes weather recordings. This then ascends high in the sky and it’s the best way for us to get weather data at high altitudes.
It reaches heights of roughly 20 miles above the surface… that’s about double the height of a jetliner! It endures temperatures as cold as -139 degrees, winds of 200 miles per hour, rain, ice, thunderstorms.. you name it!
The radiosonde measures pressure, temperature, and relative humidity. By calculating its movement, we can know how strong the wind is and in what direction it’s moving. Since the pressure is much lower with height, the balloon will expand to as large as a small house before it pops. That’s when the radiosonde will then fall with the help of a parachute at about 22 miles per hour before it hits the ground.
Roughly 75-thousand radiosondes are sent up each year in the United States. That’s two a day per weather service office. When severe weather is potential, an extra will be sent up in the afternoon so we can get an even better look at the atmosphere. When the radiosonde drops to the ground using the parachute, you’ll find printed on the side, “harmless weather instrument”. There’s a prepaid envelope where you can send it back to the National Weather Service. Only about 20% get turned back in.
This data is used by meteorologists all across the country. It’s also ingested in weather models twice a day – which are used to make weather predictions.