Friday, May 08, 2009

Mountains Emit Mesospheric Gravity Waves

Er... what? A rather "interesting" report, which can imply that it's something I've never heard before. :)

A U.S. study suggests wind blowing over mountain ranges can generate gravity waves that propagate vertically into Earth's upper mesosphere.

Researchers said such waves, known as mountain waves, have previously been observed low in the atmosphere. But Steven Smith, Jeffrey Baumgardner and Michael Mendillo of the Center for Space Physics at Boston University said their research has produced the first unambiguous images of mountain gravity waves in the upper mesosphere -- 50 to 62.5 miles in altitude.

A mass of wind can cause a "gravity wave" when blowing through mountains? Is this the same "gravity wave" that has been long sought-after by LIGO and LISA? Could they detect such a thing?

I plead completely ignorance over this phenomenon, and might try to see if I can get a copy of the paper, which isn't that easy to get based on the access that I have. Can anyone else shed some light into this?



Igor Ivanov said...

"Gravity waves" are not "gravitational waves". Gravity waves are just oscillations of a fluid in gravitational field. For example, usual water waves with wavelength of centimeters and larger are gravity waves.

zymandia said...

Good picture hereJust as a stream passing over a submerged rock can leave wake waves in the surface of the stream, so here an island bottom left causes 10-20 mile wavelength oscillations in the wind, which stay stationary relative to the ground. It is the phenomenon that took a glider to the record height of 45,000 ft +.

Tometheus said...

Gravity Wave vs Gravitational Wave

Unagi said...

As a pilot, I have actually experienced a mountain wave. I was at full power but still descending. I made the potentially risky decision to turn out of the wave (risky 'cause there's no way to know how wide the wave is and turning increases the decent rate). I finally achieved assent speed but it was a little scary. In pilot training, I learned it was due to the large volume of air moving down overpowering the lift generated by the wings. Relative to the air flow, you are "going up" but the medium you are "going up" in is going down so the net result is... going down. I don't think it's a result of gravity waves. There are way stronger forces involved. Remember gravity is a weak force. It's only seems strong on Earth because Earth is large and we are close to it (inverse square law affects gravity so distance is a factor). Compared to the size of Earth, the gravity added by a mountain would be miniscule. I'm discounting the gravity wave effect unless some more compelling evidence is presented.

Unagi said...

I should also mention that gravity is non-uniform around the globe due to the non-uniform distribution of matter. Not sure how non-uniform gravitational forces would affect "gravity waves."