The U.S. Weather Bureau station at the National Airport in 1943. Inflating a pilot balloon with hellium gas. The balloon is used for determining winds aloft. (Photo by Fred Driscoll/Courtesy of Library of Congress/PHOTO BY FRED DRISCOLL/COURTESY OF LIBRARY OF CONGRESS)

Last week’s column about the mysterious domes atop Reagan National Airport’s original terminal brought back fond memories for the District’s Polly Choate. If not for the domes — which once opened and were used in the tracking of weather balloons — it’s possible Polly wouldn’t be around.

Her mother, Marion Mellem, worked at the airport during World War II, standing in the domes to follow the balloons and take observations with a device called a theodolite.

“She was scientifically oriented and loved this work, not typically available to women,” Polly wrote.

In 1945, a man who worked at the National Weather Service headquarters on M Street NW visited the airport with his son, a Marine named Harold Choate who had recently returned from the war. Three months later, Harold and Marion were married.

Weather became a family affair. Polly’s father took observations from ships at sea and later worked at Weather Service offices in Hillcrest Heights and Sterling. Polly’s mother worked for the Weather Service, too, primarily mapping hydrological and other weather data. She retired in 1985, a year after her husband. And after Polly’s grandfather retired, he became a volunteer observer, with a weather station in his Arlington County back yard.

Tracking with a theodolite, a telescopic device used to measure angles, was eventually replaced by a radio transmitter attached to the balloon. It sent back signals that were recorded manually, and later by computer, but, Polly wrote, “a human being was always needed to fill the balloons with helium and send them up into the air.”

Speaking of which . . .

You wrote in your July 1 column that the National Weather Service launches two weather balloons per day, full of measuring instruments. What happens to those balloons when they come down to Earth? Are the instruments one-time use? How does the NWS protect animals from swallowing balloon parts?

— Kim Condas, Herndon


Every day at 7 a.m. and 7 p.m. — an hour later during daylight saving time — weather balloons are launched from 102 Weather Service sites. Each member of the flotilla carries a tiny, Styrofoam-covered box of electronics known as a radiosonde. The radiosonde transmits data on temperature, humidity and barometric pressure.

As everyone from Sir Isaac Newton to Blood, Sweat & Tears knows, what goes up must come down. The balloons are about six feet in diameter when they are launched, but as they ascend to an altitude of 100,000 feet, where the pressure is lower, they swell to 30 feet. The balloons pop, and the radiosondes float to Earth on parachutes.

The radiosonde is about the size of a milk carton. Attached to it is a self-addressed envelope that ensures delivery to a Weather Service address in Kansas, a nice central location. Some radiosondes plummet into water; others wind up in remote locations.

About 20 percent of the 78,000 radiosondes launched annually are found and mailed back, where they are refurbished and reused.

The balloon is made of a natural, biodegradable latex, which shatters into leaf-size pieces. The parachute and string are also biodegradable. The Weather Service told Answer Man that it has never received a report of an animal being harmed by a balloon.

“It’s made to have as little impact as possible,” said Chris Strong, a warning coordination meteorologist at the Weather Service’s Sterling office. Although Chris is no longer responsible for launching the balloons, he did earlier in his career, activating the machinery’s wet-cell battery by dunking it in water and connecting it to the radiosonde. Helium is typically used to loft the balloons, although hydrogen is used occasionally.

Because the Sterling office is near Dulles International Airport, the meteorologists call the airport tower to notify it of each launch.

“For a job that’s fairly computer-driven — being inside and working with computer models — it’s a good way to get outside and get in the weather,” Chris said.

Send a Kid to Camp

Another good way to get in the weather? Go to Camp Moss Hollow.

The summer camp is about 60 miles west of Washington but a world away mentally. It serves needy kids from our area, allowing them to commune with nature far from bad influences in the city.

For nearly 40 years, readers of The Washington Post have supported Moss Hollow. Your generous donation will help ensure that this tradition continues. To give, go to Click where it says “Give Now,” and designate “Send a Kid to Camp” in the gift information. Or mail a check, payable to “Send a Kid to Camp,” to Send a Kid to Camp, P.O. Box 96237, Washington, D.C. 20090-6237.

Have a question about the Wash­ing­ton area? Write Follow Kelly on Twitter: @JohnKelly. To read previous columns, go to