BISMARCK, ND (KFYR) — We are wrapping up our series of in-depth dives into how weather balloons are launched by the National Weather Service and the very useful applications of the data they collect.
Last week we showed you how balloons are prepared for launch and now we have our hydrogen-filled latex balloon with a parachute attached to a string six feet below. 75 feet below is the radiosonde, which is the instrument that measures temperature, dew point, and GPS coordinates as the balloon travels about 20 miles through our atmosphere.
Weather balloons are launched twice a day in hundreds of locations around the world, including from 68 weather forecast offices across the contiguous United States, allowing meteorologists to get a snapshot of the current state of our atmosphere.
“It’s more, kind of like a temperature measurement that you would see from your normal thermometer, but at altitude. And, it also measures humidity and it measures pressure and all that kind of stuff. So we we’re able to build a bigger 3D picture of what’s happening in real time,” said Matt Johnson, a meteorologist with the National Weather Service in Bismarck.
We launch this weather balloon at 6 p.m. so that the data has enough time to be ingested into the next update of our weather forecast models.
The ball must be thrown at these precise times, even in strong winds or in a blizzard.
“There were times when we launched into 50, 60 mph winds, so it’s pretty brutal.
Thus, the only conditions in which we could not launch a weather balloon would be a thunderstorm. We usually try to avoid launching in thunderstorms just because of the problem of lightning and the fact that you have a hydrogen balloon, but also the fact that if you launch the balloon in a thunderstorm it could also corrupt your data with the updraft. So you’re not getting a proper representation of the atmosphere, it’s a bit skewed depending on the thunderstorm,” Johnson said.
One last thing needs to be done before launch.
“We have to call Bismarck Tower to make sure we are free to throw the ball because we are close to the airport and we don’t want to interfere with international flights. So they have to give us an ‘OK’ to throw the ball. ball,” Johnson said.
“So what I do is get far enough away from the building that it doesn’t interfere with the ball. And then we kind of let it go,” Johnson said.
Now that we have a successful launch, the balloon will rise rapidly, with the first 25,000 feet, or 20 minutes of flight, being the most important as this is where most of our weather occurs. However, the balloon will continue to travel through the stratosphere before bursting once the balloon reaches approximately 25 feet in width.
The balloon can also drift more than 200 km from the release point depending on the prevailing winds at altitude. However, in calm winds, weather balloons can stay quite close to their launch point.
Once the balloon bursts, the radiosonde returns to Earth via the parachute and the radiosondes can be returned to the National Weather Service by mail.
“I think they said about 10% is returned, to maybe 5%. So most of them end up in people’s fields. They’re all biodegradable, so eventually they’ll all decompose , even the parachute, and it’s good for the environment. But it’s more of a set-and-forget system based purely on cost. It would be hard to recoup all of that,” Johnson said.
Back inside, we can start seeing our data coming from the ball.
“This is our Skew-T. We have our temperature profile here, followed by our dew point. And that’s kind of how we see the stability of the atmosphere, and we’re kind of able to plot and track and see if the environment is stable or unstable,” Johnson said.
Here’s the full Skew-T chart from our May 21 launch, with temperature in red and dew point in green from the surface down to tens of thousands of feet. The temperature lines, which are highlighted in black, are slanted and other lines on the graph help meteorologists judge how quickly temperatures are changing vertically in our atmosphere.
When the lines are closer together, there is more moisture in that layer of the atmosphere, allowing clouds to form there. Most of the ball’s flight is below zero, as shown with the area shaded in light blue.
Temperatures normally decrease with altitude in our atmosphere, but when the temperature line moves to the right on our graph, it indicates that temperatures are increasing with altitude, called an inversion, which is a stable layer of the atmosphere .
Wind speed and direction data are derived from the GPS coordinates of the radiosonde and these are plotted as the balloon rises.
These Skew-T charts are invaluable to meteorologists, especially when assessing whether conditions are favorable for severe weather. That’s why these weather balloons need to be launched twice a day, 365 days a year, to get accurate data on what’s really happening thousands of feet above our heads.
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