Lightning bolt1/26/2024 Jenkins, doctoral candidate, all in meteorology and atmospheric science.Īlso working on the project were Eric Bruning, associate professor of atmospheric science, Texas Tech University Sean Waugh, research meteorologist, and Donald MacGorman, senior research scientist, both at NOAA National Severe Storm Laboratory Xinrong Ren, physical scientist, NOAA Air Resources Laboratory Jingqiu Mao, assistant professor of atmospheric chemistry, Univeristy of Alaska and Jeff Peischl, senior professional research assistant, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder. Other researchers at Penn State include Patrick J. Clearly we need more aircraft measurements to reduce this uncertainty." The whole structure of high plains storms is different than those in the tropics. "We only flew over Colorado and Oklahoma. "These results are highly uncertain, partly because we do not know how these measurements apply to the rest of the globe," said Brune. Currently, they are not.Īccording to the researchers, "Lightning-generated OH (hydroxyl) in all storms happening globally can be responsible for a highly uncertain but substantial 2% to 16% of global atmospheric OH oxidation." If subvisible lightning occurs routinely, then the hydroxyl and hydroperoxyl these electrical events create need to be included in atmospheric models. While the researchers found hydroxyl and hydroperoxyl in areas with subvisible lightning, they found little evidence of ozone and no evidence of nitric oxide, which requires visible lightning to form. Experiments in the lab showed that weak electrical current, much less energetic than that of visible lightning, could produce these same components. What confused Brune's team initially was that their instrument recorded high levels of hydroxyl and hydroperoxyl in areas of the cloud where there was no lightning visible from the aircraft or the ground. It was known that lightning can split water to form hydroxyl and hydroperoxyl, but this process had never been observed before in thunderstorms. Most lightning never strikes the ground, and the lightning that stays in the clouds is particularly important for affecting ozone, and important greenhouse gas, in the upper atmosphere. "Now there is increasing interest in the weaker electrical discharges in thunderstorms that lead to lightning bolts." "Through history, people were only interested in lightning bolts because of what they could do on the ground," said Brune. Visible lightning happens in the part of the anvil near the thunderstorm core. The researchers report their results online today (April 29) in Science First Release and the Journal of Geophysical Research - Atmospheres.īrune notes that airplanes avoid flying through the rapidly rising cores of thunderstorms because it is dangerous, but can sample the anvil, the top portion of the cloud that spreads outward in the direction of the wind. "With the help of a great undergraduate intern," said Brune, "we were able to link the huge signals seen by our instrument flying through the thunderstorm clouds to the lightning measurements made from the ground." Then they did a reanalysis of the thunderstrom and lightning dataset. The data was from an instrument on a plane flown above Colorado and Oklahoma in 2012 looking at the chemical changes that thunderstorms and lightning make to the atmosphere.īut a few years ago, Brune took the data off the shelf, saw that the signals were really hydroxyl and hydroperoxyl, and then worked with a graduate student and research associate to see if these signals could be produced by sparks and subvisible discharges in the laboratory. "We assumed there was noise in the instrument, so we removed the huge signals from the dataset and shelved them for later study." Brune, distinguished professor of meteorology at Penn State. "Initially, we looked at these huge OH and HO 2 signals found in the clouds and asked, what is wrong with our instrument?" said William H. OH is the main driver of many compositional changes in the atmosphere. The hydroxyl radical is important in the atmosphere because it initiates chemical reactions and breaks down molecules like the greenhouse gas methane.
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