May 7, 2009

Mountains emit mesospheric gravity waves

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.

The scientists said they observed the gravity waves using all-sky images from the El Leoncito Observatory in Argentina. They said they observed a large series of stationary waves spanning a 6.9-mile range.

The researchers said the large band-like waves lasted several hours each night and did not propagate across the sky -- features that distinguish mountain waves from other types of atmospheric disturbances.

The study appears in the journal Geophysical Research Letters.