CORVALLIS, Ore. - For the first time, scientists at Oregon State University are measuring atmospheric temperatures with fiber optic thermometers suspended from unmanned aircraft--combining two emerging technologies to probe a poorly understood swath of Earth's atmosphere.
With funding from the National Science Foundation, John Selker is buying two new unmanned aerial vehicles (UAVs) to loft sophisticated measuring instruments of his own design into an atmospheric zone that's been hard to study until now.
"These two technologies together will add orders of magnitude to the precision and resolution of our atmospheric measurements," said Selker, a hydrologist and professor in OSU's College of Agricultural Sciences. "We'll be able to take a continuous slice of data through space and time, getting information that no one has been able to capture before."
The high-powered thermometers use a down-to-earth technology: fiber-optic cable, similar to that used for telephone and internet communication. By measuring tiny pulses of light zipping along spun-glass strands, the fiber cables capture thousands of temperature readings along their length, detecting differences as slight as 0.01 degree Celsius.
In early-morning test flights near Hermiston, Selker's OSU colleagues Michael Wing and Chad Higgins suspended a 400-foot sensing cable--not much thicker than a kite string--from an OSU-owned quad copter. They flew the aircraft at 30 miles an hour, sending it high enough that the tip of the cable just touched the ground. The cable reported temperatures every 13 centimeters.
The researchers started their flights at sunrise because they wanted to see how the atmosphere develops in the boundary layer, the lowest portion of Earth's atmosphere, as the sun's heat begins to move the air.
The Earth's surface and near atmosphere--up to about 1,000 meters above the ground--is a critical zone of feedbacks between air, water and earth, Selker said. "It's where processes interact, where synergies occur. And temperature is a critical driver of these interactions."
Until now, he said, scientists have had a hard time taking comprehensive measurements of the lower atmosphere.
"Typically, you'd have to take readings from a fixed point, a tower or a balloon," Selker said. "Now, instead of measuring one or two or three points at a time, we can measure a million points."
Such detailed measurements promise to shed light on how clouds and rainstorms develop, how air pollution gets diluted, how pollen moves across the landscape and other important atmospheric dynamics, he said.
Selker's sensors have captured data from land and sea--an old-growth forest canopy, the Pacific Ocean floor, Antarctica's Ross Ice Shelf. Until now, there hasn't been an easy way to deploy them in the air.
UAVs equipped with fiber-optic sensors represent "a fundamentally new way to look at the lower atmosphere," Selker said. "It's like living with 20-200 vision and then getting a good pair of glasses. You see a different universe."
UAVs--popularly known as drones--are best known for their military uses, but they have found many civilian applications, including precision agriculture, traffic surveillance and wilderness rescue. They are a boon to environmental scientists, Selker said, because they can carry measuring instruments into places where it's difficult or dangerous to send humans, or where other technology can't easily reach.
Selker's UAVs will join a growing suite of instruments and tools at the Center for Transformative Environmental Monitoring, or CTEMPs, an NSF-sponsored partnership between OSU and the University of Nevada-Reno. CTEMPs has a fleet of scientific instruments that it makes available, along with training, to environmental scientists throughout the United States.
Selker is a co-director of CTEMPs along with Scott Tyler of the University of Nevada. Wing is director of AirCTEMPs and directs UAV flights at OSU for agriculture, engineering, fish, wildlife and natural resource applications.
The $1.2 million NSF grant renewal will also fund CTEMPs's purchase of other UAV-mountable instruments, including thermal imaging cameras and a small LIDAR, or laser-powered imaging tool, that captures three-dimensional measurements of landscape features.
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