by George Zamora
SOCORRO, N.M., Feb. 26, 2007 – Researchers at New Mexico Tech’s Langmuir Laboratory for Atmospheric Research have studied lightning in thunderstorms for more than 40 years, but now, for the first time since the early years of the research facility, atmospheric physicists at the mountaintop lab near Socorro have compiled, analyzed and published their scientific observations of lightning occurring during a volcanic eruption.
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Although the phenomenon of volcanically induced lightning has been known for centuries, a study by university researchers Ronald Thomas, Paul Krehbiel, William Rison and colleagues published in the current issue of the prestigious journal Science provides new data and fresh insights into volcanic lightning associated with one of last year’s eruptions of Alaska’s Mount St. Augustine.
Following the initial eruptions of the Augustine Volcano in early January 2006, the Langmuir Lab research team, working in collaboration with scientists at the Alaska Volcano Observatory, quickly decided to travel way up north to set up a pair of portable lightning-monitoring stations at sites near Homer and Anchor Point, Alaska, about 60 miles across Cook Inlet from the island volcano.
As luck would have it, Mount St. Augustine erupted again on January 27, 2006, with the monitoring stations already set up and listening for telltale radio signals from the volcano.
“Despite snowy conditions and the temperature not getting above zero, we got the stations set up and operating in two days,” said Paul Krehbiel, a member of the research team and co-author of the Science paper. “We finished the final set-up just in time to be able to monitor that second series of eruptions.
“People in Alaska pay close attention when one of their volcanoes starts erupting, and we got excellent cooperation from everyone we worked with,” he added.
The two portable lightning monitors employed in the volcanic lightning study are smaller versions of Langmuir Laboratory’s Lightning Mapping Array (LMA) system, which is now being used at several locations across the United States for early detection of severe thunderstorms and lightning. Most recently, the Langmuir group has collaborated with NASA to set up a lightning monitoring network for the National Weather Service in the greater Washington, D.C. metropolitan area.
The three-dimensional mapping capabilities of the LMA allows scientists and technicians to generate detailed analyses of individual discharges of lightning, as well as an ongoing record of total lightning activity.
Up to thousands of individual segments of a single lightning stroke can be mapped with Langmuir Laboratory’s LMA system and later analyzed on high-end computers to reveal how lightning initiates and spreads throughout a thunderstorm . . . or within a volcanic plume.
“We just happened to be at the right place at the right time with the right equipment,” said Ronald Thomas, lead author of the Science paper.
“There were four eruptions that we eventually got good data on, but the first eruption was the most energetic one we measured, and was the one that produced the most lightning,” Thomas said.
During the strongest eruption, the New Mexico Tech lightning researchers observed more than 300 lightning discharges within the Augustine Volcano’s smoke plume, a maelstrom of hot air, gases, moisture, dust and ashes which first floated upwards of 30,000 feet and then drifted across the line-of-sight of the two monitoring stations.
“All that volcanic material coming out charged from the volcano and being injected into the atmosphere during an eruption creates something like a thunderstorm,” Krehbiel related. “Some scientists have even coined the term ‘dirty thunderstorm’ to describe this effect.”
In their study, the Tech researchers also discovered a different kind of volcanic electrical discharge, which seemed to emanate from the mouth of the volcano during the violently explosive, eruptive phases.
“There’s stuff coming out of the volcano that’s highly charged as it’s coming up, so there’s some mechanism in there that’s making it come out charged,” Thomas said, “but it’s not quite lightning. It’s something different.”
In another stroke of good fortune, one of the lightning-monitoring stations to measured interference effects caused by the radio frequency pulses reflecting off the water surface of Cook Inlet, providing a more detailed “picture” of the entire lightning structure.
Researchers associated with the early years of New Mexico Tech’s Langmuir Laboratory, specifically Charlie Moore, Marx Brook, and Bernard Vonnegut, were involved with some of the first scientific investigations of volcanic lightning made during the Surtsey and Heimaey eruptions in Iceland in 1963 and 1973.
Cited as co-authors of the recent Science paper, along with Thomas, Krehbiel, and Rison, are Langmuir Lab researchers Graydon Aulich and William Winn, and New Mexico Tech doctoral candidate Harald Edens, as well as Alaska Volcano Observatory scientists Steven McNutt, Guy Tytgat, and Ed Clark. Important contributors to the project were Tech undergraduate students Nicholas O’Connor and Matthew Briggs, and Sandra Kieft of the Langmuir Laboratory Office.
Langmuir Laboratory, which was established at New Mexico Tech in 1963, is widely considered the preeminent lightning research facility in the United States, and is recognized worldwide for its numerous contributions to the scientific discipline of atmospheric physics.