Short Stuff: Weather Balloons

Key takeaways

A radiosonde combines temperature, humidity, air-pressure, and radio-transmission equipment in a small package carried by the balloon.
Weather balloons reach roughly 18 miles high, where upper-air disturbances can be detected before they produce dangerous storms at the surface.
Their low cost enables roughly two launches per day at 92 U.S. stations, but spent balloons and instruments can become widely scattered litter.
Hydrogen is cheaper and offers more lift than helium, but its flammability makes helium the safer filling gas.

Summary

A weather balloon is mostly a carrier for the radiosonde

Josh, Chuck, and guest host Jerry introduce weather balloons as a cheap, essential “workhorse” of weather observation. The balloon carries a shoebox-sized instrument package called a radiosonde. Inside are a thermistor for temperature, a hygristor for humidity that measures electrical resistance through a lithium-chloride film, an aneroid barometer for air pressure, and a radio transmitter that sends the readings to the ground. The hosts joke about whether “radiosonde” is pronounced the French way and about the unspecified size of the shoebox.

Why balloons rise to the stratosphere and then burst

The hosts explain that a weather balloon begins at roughly five feet in diameter but expands until it can be as large as a moving truck. It rises to the stratosphere, about 18 miles up, where the surrounding air pressure is much lower; eventually the balloon bursts. A small parachute lets the radiosonde descend more gently, although the data has already been transmitted, so weather agencies do not need to recover the device. This is much faster than earlier methods using kites or airplanes, which had to return before readings could be analyzed.

High-altitude readings provide earlier storm warnings

Chuck says balloons are released high because conditions above a sunny-looking ground location can reveal disturbances that will develop into severe thunderstorms or tornadoes. Those measurements give forecasters more time to warn people than ground observations alone. The hosts say the system costs only a few hundred dollars per launch and is used roughly twice daily at 92 U.S. stations, producing about 67,000–68,000 launches a year; more than 900 stations worldwide perform similar observations.

Hydrogen lifts better, but helium avoids the fire risk

The balloons are made from neoprene, a synthetic rubber, and filled with either hydrogen or helium. Hydrogen is cheaper, provides slightly more lift, and can be extracted more easily from water, but its flammability—famously illustrated by the Hindenburg—makes helium the safer choice. The hosts note the environmental downside: balloons and instruments can travel hundreds of miles on wind currents and become litter. Recovering them with trucks or helicopters would undermine the low-cost design.

A lawn-chair flight reached 16,000 feet

The hosts mention that recovered radiosondes come with a postage-paid envelope so finders can mail them to the National Weather Service, which can send the equipment up again; Chuck says finders also receive a junior weather-service-operator T-shirt. They close with Larry Walters, a truck driver who in July 1982 tied 42 weather balloons to a lawn chair intending to float from Los Angeles toward the Rocky Mountains. He rose to 16,000 feet, dangerously cold and unprepared, then used an air gun to shoot balloons and landed in a Long Beach backyard.

Show notes

Weather balloons are the workhorse of the meteorological world, which is why they’ve been used daily around the world for most of a century. Let’s salute these unsung heroes of weather prediction by getting to know them better.

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