Scientists Decode The Physics Of Wave Surfing Pelicans
Monday, May 10, 2021
Photo by KPBS Staff
The top of the bluff just south of the Torrey Pines Golf Course is a special place for those looking to take a leap off a cliff to fly.
The combination of a cool ocean, hot land and a steep bluff make it possible.
“Inland heats up and all that cool ocean breeze goes east,” said Vito Michelangelo, flight director at Torrey Pines Glider Port. “And that’s what creates the magic here for us. Soaring. As paragliding pilots.”
The grassy field on top of the bluff serves as a launching pad for hang gliders and model planes — anything that can ride a stiff ocean breeze that climbs the cliff face.
“It’s a classic,” said Michelangelo. “Everybody’s seen a bird just circling up in a lift and that’s typically what we do when we’re flying.”
Would-be fliers frequently look to birds to get clues about daily flight conditions. If there is not enough lift the paragliders just gradually float to the beach.
That’s because birds take advantage of the updrafts to conserve energy.
Pelicans gracefully glide along breaking waves, riding the wind to cover huge distances without flapping their wings.
The sea birds caught the eye of UC San Diego doctoral student Ian Stokes when he used to surf near Santa Barbara.
He noticed how the birds used the wind created by the waves.
“So here the wave breaks,” Stokes said as he pointed to video footage of the birds floating above moving waves. “And they send it up to higher elevation. And they soar back down to the next crest. And there they go.”
When one wave taps out, the lift carries the birds up so they can get to the next wave.
“Right, so they’re all banking back up and getting off the back,” Stokes said. “And they’re swooping into the next wave. Then they take off again and start their ride once again.”
Pelicans take advantage of the same forces at play along the glider port cliff.
There, surface winds hit the bluff and go up. That creates ideal conditions for paragliders.
On the ocean, moving waves act like the cliff and they push air at the surface of the ocean up as they roll toward the shore.
The pelican’s flight highlights the delicate interplay between the ocean and the atmosphere.
“That exchange of energy between the ocean and the atmosphere is a very prominent driving force in the way that our climate responds to different environmental signals,” Stokes said.
“Scripps Institute of Oceanography has a long history of research around the idea of ocean waves and the atmosphere interacting,” said UC San Diego engineer and Scripps Institute of Oceanography researcher Drew Lucas.
Lucas worked with Stokes to refine an algorithm that explains the physics of how the system works.
“It’s an equation that relates the form of the ocean wave, its speed and size and its length, which we call its period or wavelength, to the amount of wind that is created in the atmosphere and it’s an equation,” Lucas said.
The birds use the uplifting air to keep them aloft when the waves rise and then crest near the shore.
The ocean and atmosphere are coupled systems that researchers have been studying for years.
“We’re in the business of trying to predict the future of the Earth’s climate and the ocean-atmosphere system,” Lucas said. “And those are problems related to how the ocean and atmosphere are communicating information, energy and properties.”
Understanding the mechanics of this pelican behavior scientists understand more about the planet.
The knowledge might be valuable to drone developers seeking to design better aircraft and it may also provide input into what might be happening as the ocean and climate change.
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