Aerial Prospecting
Tailor-made technology reveals atmosphere’s hidden story.
Digging for gold in the 1900s required only a shovel, a pan, and lots of grit, but hunting out minerals in the skies demands a slightly more sophisticated set of tools—the most important being a Light Detection And Ranging instrument known as a lidar.
Where radars use radio waves to determine the range, altitude, direction, or speed of a distant object, lidars use laser light to retrieve the same information—and much more.
“A lidar is a perfect tool for studying the atmosphere,” said CIRES Fellow Xinzhao Chu, whose research group focuses on lidar technology development and the study of atmosphere. “This laser beam directed into clear skies can tell us about the types of matter tens to hundreds of kilometers above Earth’s surface.”
Ten years ago, Chu and her colleagues developed a highly specialized instrument—the Fe (iron) Boltzmann temperature lidar—to measure the key atmospheric variables in the middle and upper atmosphere, such as iron and sodium, necessary for monitoring climate. The lidar detects these and other minerals in the atmosphere, and these particles give valuable information about their immediate environment.
“Each particle tells its own individual story,” Chu said. “They are one of the essential tracers to detect temperature and waves in the upper atmosphere.”
The team first set up their iron lidar system at the South Pole in 1999, at Rothera near the Antarctic Peninsula in 2002, and then the research group upgraded the instrument and installed it at the U.S. research base, the McMurdo Station, in 2010. The McMurdo Station, which lies at approximately 78° S latitude, is about halfway between the South Pole and the Antarctic Circle.
“The atmosphere in Antarctica was so difficult to measure in the past that people were basically guessing at what was going on,” Chu said. Finding this vital piece of the puzzle—the atmosphere in different regions of Earth can differ greatly—is an essential step in mapping Earth’s atmosphere in its entirety, she said. “We have to gain a fundamental understanding of how the atmosphere is working before we can predict future scenarios,” she said.
The research team split their time between Boulder, Colo., and the McMurdo Station, with a member of the group overwintering at the base to collect the maximum amount of atmospheric data. In 2011, the team “struck iron.”
CIRES Environmental Observations, Modeling, and Forecasting (EOMF) Division
Chu’s research lies under the umbrella of EOMF—a CIRES division that is focused on understanding the interactive processes in Earth’s physical environment and developing a picture of its sensitivities to natural and anthropogenic change.
“Xinzhao Chu’s research is an excellent example of the type of research carried out by EOMF scientists, who look to apply observational and modeling techniques to improve understanding and prediction of Earth’s processes,” said EOMF Director Mike Hardesty.
EOMF researchers have used these techniques to study important issues such as the potential climate effect of leakage from wells in large natural gas fields; improving understanding of the exchange of carbon dioxide between the land and the atmosphere; and translating climate information into tools for sustainable development of water resources, Hardesty said.
Instead of finding the iron atoms in the mesosphere or lower thermosphere, the team found them, in abundance, up to 155 kilometers high—deep into the thermosphere—an entirely unexpected discovery.
“Something unique is happening here,” Chu said. “We found more particles than we ever imagined.”
The scientific community believes the iron atoms are from cosmic dust—broken-up meteors. As the meteor enters the atmosphere, it passes through the upper and lower atmosphere, and the iron particles eventually settle on Earth, Chu said. In the southern hemisphere, this means settling in the ocean.
As iron-rich particles provide nutrition for plants and small animals, Chu believes the team may have identified a major source of fertilization in the Southern Ocean. “What we are studying is part of the cosmic dust, and this cosmic dust is part of what fertilizes Earth,” she said.
While conditions at the McMurdo Station can be harsh, with temperatures in the wintertime getting as low as minus 50° Celsius and the scientists work long hours, Chu said the scenery and wildlife provide a pleasant distraction. “The mountains are gorgeous—you just can’t stop taking photos,” she said.
And then there’s the company—the black-and-white, web-footed kind.
On one trip, a penguin faced off with two officials on the airport runway and refused to move, she said. On another, four emperor penguins lined up alongside the plane to “see Chu off” on her trip back home. “Every time you see a penguin, it lifts your spirits,” Chu said.
