The photo was taken from a sailplane at a place called Flock Hill in the South Island of New Zealand. The Southern Alps are in the background.
John McCaw
THE GIST:
- Mountain waves have big effects on weather.
- Sailplanes ride mountain waves, making them ideal for collecting data.
- Sailplanes can fly higher than any other aircraft, theoretically to 100,000 feet.
The quest to pilot a sailplane to the edge of space is now paying scientific dividends, as data is revealing 3-D details on roiling atmospheric "mountain waves," which influence weather, create turbulence for air traffic and even affect the ozone layer.
A sailplane piloted by Einar Enevoldson and the late Steve Fossett soared to almost 43,000 feet (13,000 meters) using mountain waves east of the Sierra Nevada mountain range in California in 2003. The planes were equipped to record altitude, temperature, airspeed, position and time.
That data has now been crunched to shed new light on mountain waves, now published in the latest issue of the Journal of Atmospheric and Oceanic Technology.
Mountain waves are created when steady winds flow over a mountain range, explained the lead author of the study, Rick Millane of the University of Canterbury in Christchurch, New Zealand.
When the air descends on the lee (sheltered) side of a range, buoyancy forces the air to find the same altitude at which it started, but the air then tends to overshoot and ascend too high. The overshooting air then descends again and overshoots too low, then rises again and overshoots high, then sinks and so on, creating a series of updrafts and downdrafts that run parallel and downwind of the mountains.
"It's like a spring, basically," Millane told Discovery News.
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Along the lee sides of long north-south running ranges like the Sierra Nevada or those of New Zealand or Patagonia, you sometimes get lines of mountain waves hundreds of miles long.
Naturally, these places are magnets for sailplane enthusiasts because the updrafts allow sailplanes to rise to incredible heights and fly great distances. And because the pilots explore the waves when they fly, they are the perfect platform for gathering information that can then help to fine-tune and test meteorological and climatic models.
"There are thousands of glider flights around the world," said Millane.
There are even competitions where 30 or more gliders will fly in the same area. Large amounts of data can be collected under such conditions, he said.
The mountain wave study also proves how useful sailplanes could be for collecting data at much higher altitudes, says meteorologist Elizabeth Austin of WeatherExtreme.com.
"With sailplanes we can penetrate into the stratosphere,” said Austin, who serves as the official meteorologist for the Perlan Project, which aims to fly a sailplane to 100,000 feet (30,500 meters) and into the stratospheric polar night jet -– a current of air surrounding the Antarctic and Arctic in their respective winters.
Normal powered aircraft can't fly that high because there is not enough air to generate lift on wings to carry the weight of fuel and engines -- unless the plane is some sort of hypersonic airplane of the future, that is. Sail planes, on the other hand, are just right for the job.
"We can fly a sailplane to 100,000 feet," Enevoldson told Discovery News. "We fly higher than any powered aircraft can fly and carry along instrumentation to study chemical processes."
To prove it, Fossett and Enevoldson, wearing pressure suits, set the current world-record altitude for sailplanes of 50,671 feet (15,447 meters) in August 2006. At that altitude the suits became too stiff and the temperature too frigid to go any higher, explained Enevoldson.
What's needed is a new kind of sailplane with a pressurized and heated cockpit. The Perlan Project is already halfway through building just such a plane, said Enevoldson.
If funding is found to finish the plane by 2011, he and other pilots might soon be exploring realms of Earth's atmosphere previously only accessible by helium balloons.
Tags: Air Travel, Aircraft, Earth, Mountains, Wind
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