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May 2, 2011 / Dave Gorham

Weather Balloons Still Going Up…and Up

I’ve launched a few weather balloons in my day. Let me tell you, it’s every bit as fun as you think it is.

It’s been more than 25 years since I launched my last weather balloon, yet I remember it vividly. I was stationed at Camp David, providing weather support to the President’s helicopter, Marine One. Ronald Reagan and his staff were inbound from the South Lawn of the White House, but the weather at the Camp David landing zone was inclement — low ceilings with drizzle and rain threatened the safety of crew and passengers by severely restricting the visibility of the pilots. The exact altitude of the cloud base was needed and so the balloons were launched, one at a time every few minutes; the time to their disappearance into the clouds was noted and the results radioed to the pilots of Marine One and operations at Quantico, Virginia. With a known rate of ascent, the bases of the clouds could be determined with a high level of accuracy as the balloons disappeared into the heavy clouds.

Though highly specialized, this ceiling balloon doesn't look much different than a party balloon. Image: Wikipedia

Marine One lifts off from the South Lawn of the White House. Photo: Wikipedia

Though technically a weather balloon, this sort of ceiling balloon is not usually the type that comes to mind when one thinks of weather balloons. Or, maybe it is. Maybe the other type of weather balloon is a mystery to most? Outside of school, I’ve never seen the “other type” of weather balloon and it’s the Mac Daddy of weather balloons. These balloons rise so high that as the outside air pressure decreases, the gas inside the balloon expands so much that the balloon finally bursts. They are launched twice daily from about 800 locations across the globe and rise to altitudes of about 25 miles. In this country (excluding Alaska, Hawaii and Puerto Rico) that equates to more than 50,000 launches each year (69 launch sites x 2 per day x 365 days per year = 50,370 launches). You’d think, even by accident, I would eventually come across one of these things. (Then again, I’ve been a meteorologist for about 30 years and I’ve never seen a tornado in person, either. And I’ve lived in Oklahoma and Texas for almost 25 of those 30 years!)

Note: As mentioned, weather balloons typically burst at about 25 miles in height (120,000-130,000 feet). Beyond this altitude, radiosonde rockets are used. Beyond the reach of rockets, satellites use infrared and other sensors to track atmospheric characteristics.

High-altitude weather balloons originated sometime around World War II. Some reports have the first launch occurring about 60 years ago, while some reports indicate the first launch occurring at about the time WWII was beginning. Either way, their purpose then remains their purpose today: Launch a radiosonde into the atmosphere to record atmospheric data such as temperature, humidity, pressure and wind speed at various altitudes by way of a small, expendable radio transmitter. (Radiosonde data does not include wind speed. This data is derived from tracking the balloon by radar, GPS and/or radio directional findings.)

The radiosonde. Inexpensive and built to be reused, only about 20% are ever returned. If you find one, follow the return instructions printed on the box. Image: NOAA

These 3-letter identifiers indicate stations in North America that launch weather balloons twice each day. Image: University of Wyoming

The received data is then entered into computer models where it is combined with radiosonde data from around the world and output into graphical images of atmospheric motions. In addition, human weather forecasters can analyze the data for more specific information for a specific location. An upper air sounding, plotted as a Skew-T or other thermodynamic program, is a common and useful tool for every weather forecaster as it shows the temperature, humidity, wind speed and direction at given altitudes for a given location. In the old days (my day) it was hand-plotted and hand-analyzed — an agonizing process! Today it’s done in an instant, thanks to high-speed computers.

 

The Mac Daddy of weather balloons will lift a radiosonde to about 130,000 feet before the balloon bursts - allowing the radiosonde to fall back to Earth. Surprisingly, I've never heard of a radiosonde landing on a roof or destroying a car. Only 20% of the small units are returned for reuse. Image: Wikipedia

You’ve likely heard every television meteorologist blame or thank the computer models for the failure or success of his or her forecast. It’s these models, fed by the twice-daily balloon launches, to which the meteorologist is referring. From an overnight freeze, to severe thunderstorms, to a hurricane landfall, it’s the rare forecast that doesn’t rely significantly on computer models. You may then wonder, “If the forecast is based on the computer model, why do I need a weather forecaster?” Simply, no computer model can handle every situation in every location with aplomb. Certain models excel in certain locations, certain models excel at certain times of the year, certain computer models excel with a certain type of weather. A model that, for instance, works well forecasting hurricanes may fail at forecasting tornadoes. It’s the skilled meteorologist who knows which model (or models) to exploit at which times.

You may also have heard how the accuracy of weather forecasts is improving every few years. This is due, in large part, to the improved performance of the computers that handle the radiosonde data. Imagine the numbers that are gathered and manipulated: 800 launching sites, two launches daily, 365 days per year, with data recorded from the surface of the Earth to approximately 130,000 feet. Staggering! The faster the computers can ingest the information, the faster they can process it, then the faster the forecasters can analyze it and the faster the computers will be ready for the next set of data. Perhaps someday there will be three launches per day? Four, maybe?

Hot air balloons first carried man aloft in 1783. And now, for the past 70 years, hydrogen-filled (sometimes helium-filled) balloons have been carrying scientific sensors and transmitting equipment aloft. Old school technology for sure, yet firmly embedded in one of the most high-tech sciences of today.

YourWeatherBlog has written about weather balloons before. Click here for “Seen Over Houston: That Ain’t No Blimp.”

 

 

 

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