WRAL WeatherCenter Blog

Weather balloons: What goes up must come down

Posted July 12, 2012

We spend a lot of time talking about what it's doing outside: "It's 85 degrees" or "the dew point is 63 degrees" or "the wind is from the southeast at 7 mph," and so on.

Because we make these observations near the ground (and usually at airports – but that's a different blog post!), we call them surface observations. However, we all know the atmosphere doesn't just exist here close to the ground, and what happens aloft can and does affect the weather here on the ground.

That's why the National Weather Service sends up balloons from a few dozen sites across the country twice a day, in coordination with other weather forecasting agencies around the world. These balloons have small instrument packages attached to them that record temperatures, dew points and pressures as they rise. These data are used by meteorologists and computer models to assess the current state of the third dimension of the atmosphere and aid in forecasting future weather.

Of course, these balloons don't just keep on going forever. Eventually, due to the lowering pressure outside, the balloon expands and expands until it eventually pops. Some folks in Florida tracked one of these balloons all the way up and, through a telescope, captured what it looked like when it popped. And no, the instrument package doesn't plummet to earth. An attached parachute helps it fall gently. Only about 5 percent of them are ever found and returned; those that are returned are reused.


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