Nearly 250 years after Benjamin Franklin flew a kite to sample the electric fields in a Pennsylvania thunderstorm, meteorological kites are again flying high as platforms for scientific research.
Used for fun for thousands of years, kites were first launched in the interest of science in Scotland in 1749 when Professor Alexander Wilson and his student Thomas Melville deployed a string of paper kites, each carrying a thermometer, on a single tether. The thermometers were released at set altitudes by a high-tech trigger -- a smoldering fuse. Cushioned with paper, the thermometers crashed to Earth where the scientists -- if they were nimble enough to recover the thermometers in time -- obtained a rough atmospheric temperature profile.
Our money says it was really grad students who went chasing, not the august Professor Wilson, but let's get on the with the story.
After Franklin, kites were used only sparingly for scientific purposes until the twilight of the 19th century, when they became a meteorological mainstay in the United States and Europe. In the United States between 1900 and the 1930s, 17 meteorological stations east of the Rockies used kites to probe the atmosphere and routinely measure temperature, pressure and relative humidity.
But in the 1920s the advent of high-flying weather balloons and aircraft equipped with a passel of meteorological instruments put a deadly damper on the use of meteorological kites, according to Ben Balsley, a University of Colorado scientist. Moreover, the deployment over the last few decades of a constellation of weather satellites, capable of instantly reading large swaths of the atmosphere, seemed to obviate the need for such low-tech platforms.
But when it gets right down to it, kites are more fun than satellites, and over the last decade, 60 years after meteokites were stashed in the basement, Balsley and a handful of other atmospheric scientists have dusted off kite technology. Once again, kites are contributing to studies of everything from electric fields to trace gases like ozone. "It's a proven technology," says Balsley. "It's just been forgotten."
But why, we ask, revert to an age-old toy when most meteorological scientists are lining up to use satellites and aircraft that can skip to the top of the atmosphere?
Because kites can do things that satellites, aircraft and balloons can't, according to Balsley who recently spoke about the resurrection of scientific kites at the Council for the Advancement of Science Writing's New Horizons in Science Briefing in Hershey, Penn.
"At high altitudes, balloons get blown around and satellite resolution isn't good enough," says Balsley. In addition, putting pricey scientific instruments aboard instrument packages called radiosondes, which are not tethered and rarely recovered, can put a serious dent in your research grant. Meteorological kites have other advantages, too:
- They're cheap.
- They provide a stable platform.
- They can provide a continuous read of a cross section of the atmosphere since kites can sometimes be kept aloft for days at a time.
- They can be used over land, water or ice.
- Modern kites can reach dizzying heights, hoisting scientific payloads as high as several kilometers.
- They're low-tech, perfect for work in remote regions.
The new generation of kite-flying weatherfolk have added their own technological twists to scientific kite flying. Some kites are huge, parafoils capable of carrying payloads as heavy as 23 pounds. Tiny sensors can be attached to kite tethers to profile things like electric fields. Remote-controlled trams -- aerodynamic, payload-carrying devices that scurry up or down a kite's tether on command -- have enhanced scientists' ability to sample the atmosphere. Data can be radioed to the ground or recorded on board.
Beyond gathering weather data, some scientists are using kites to hoist insect traps high into the atmosphere to study insect migration. Others have lofted ultrasonic microphones to eavesdrop on feeding bats.
The scientific kite, argues Balsley, is back as a bona fide scientific tool. And in some circumstances, where high-resolution measurements of atmospheric conditions or chemistry is needed, there's no better way to get those data than to go fly a kite. Sounds like our kind of work!
-- Terry Devitt