One of the world's most advanced scientific instruments - a laser that shoots a green beam far into the night sky above Utah State University, Logan - is helping unlock secrets of the atmosphere.
Vincent B. Wickwar, a USU professor in both the physics department and the Center for Atmospheric and Space Sciences, said Thursday the laser is studying two strange phenomena:- Mysterious temperature inversions that are invisible from Earth, which are much higher in the air than the type most people know about.
- Rapid oscillations of parts of the air, almost like waves.
Wickwar spoke at the Salt Lake Marriott during a four-day meeting on optical remote sensing of the atmosphere, which ends Thursday.
The laser is used in a system called "lidar," for light detection and ranging.
The device is run by Consortium Lidar, which includes Wickwar at USU; Thomas D. Wilkerson of USU and the University of Maryland, College Park; John Meriwether at Clemson University, Clemson, S.C.; and David Rees, University College, London.
Project funding comes from the institutions and the National Science Foundation.
Mounted atop the USU Science Building, the laser sends bright pulses that reflect from atmospheric layers high above the ground. It has been operated since August 1993.
How the pulses are scattered when they reflect back into the tube of a telescope on Earth tells much about the nature of particles in the air and about the temperature. Scientists can determine temperatures at many different altitudes.
"We're able to get up as high as 90 kilometers (55 miles) at the moment," Wickwar told the group. "We've carried out measurements to those incredibly high altitudes."
USU was selected for the instrument because "we are in a valley that's very clear and it's above most of the haze," he said. Also, Logan has "good seeing conditions, compared with where other members of the consortium are located."
Another advantage is that the university is in the middle of the mountains, and the winds fluctuate as they cross the peaks. That improves the chance for the occurrence of the atmospheric waves, which may be set off by the breezes.
Big temperature inversions show up during the winter in the mesosphere about 30 to 37 miles above the ground, according to data collected by the lidar.
In the summer, the inversion is more like 50 miles up, and it's different.
During a Deseret News interview after his talk, Wickwar said the summer inversion is "much less frequent and much smaller and it's at much higher altitude."
The inversions, or temperature changes, aren't new. They were discovered by sounding rockets years ago.
"Various rocket experimenters would have their classic `bad data points,' " he said.
Atmospheric temperature checks radioed by the rockets would show a smooth drop-off as the rocket ascended, but then "suddenly there is an increase in temperature." The rocketeers figured this was a mistake in the data.
But eventually it happened frequently enough that the change in temperature was determined to be an actual difference in the mesosphere. In 1988, French scientists published a review of all the readings.
Since then, lidars like the one at USU have been reporting information about the inversions.
"The big question is, what are they?" Wickwar said.
"Where do they come from? And we don't have an answer yet. We're putting a lot of attention to that and hopefully we'll be able to add something to that in the next few months."
He speculated that the winter inversions might be because of something like waves in the atmosphere, while the summer inversions might be caused by chemical changes. Hydroxide in the air may be involved, he said.
More may be known about these unusual layers when the lidar at USU is upgraded. It is about to get a more powerful "Alexandrite" laser, which should be able to reach higher into the atmosphere, and a steerable, four-barrel telescope that will be able to improve data collection by 30 times.
The telescope is being built by Custom Optical Fabrication in Salt Lake City, with direction from Eugene L. Loh, the University of Utah physicist who runs the "Fly's Eye" cosmic ray detecting project in the Western desert.
Do the inversions occur worldwide? At the middle latitudes, they have been seen over many parts of the Earth, with satellites detecting the inversions. Satellites report that the inversions don't seem to exist at higher latitudes, Wickwar said.
"But talking to a friend who has a lidar in Greenland, they have seen it once or twice," he added.
Wilkerson, also interviewed at the conference, noted, "There are only a few lidars scattered around the globe that are capable of doing this."
The meeting was sponsored by the Optical Society of America in cooperation with the American Meteorological Society. It drew 110 scientists, some from as far away as Switzerland and Japan. Among those on the agenda were specialists from Brigham Young University, the University of Utah and USU.