Research findings strike upon lightning-frequency prediction

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Adding to a growing literature on the subject, another study has forecast an increase in extreme weather due to climate change. In particular, the research struck upon a simple new model to predict the frequency of lightning strikes.

A straightforward relationship between measures of atmospheric instability and precipitation reported by campus researchers predicts a 50-percent increase in lightning strikes within the contiguous United States by the end of the century. Campus assistant professor of earth and planetary science David Romps and his colleagues published their findings in Friday’s issue of Science.

The researchers took the product of two measures — available potential energy and the precipitation rate — and found they could predict 77 percent of the variation in lightning strikes from the metric.

Romps, who studies atmospheric dynamics at the Lawrence Berkeley National Laboratory, originally started looking at the amply available lightning data to understand the climate. The converse, however, proved compelling.

“We realized that the study of the reverse arrangement might be more interesting — that maybe we could predict lightning based on these two things,” Romps said, referring to atmospheric instability and precipitation data.

They tested their prediction using precipitation data from the National Weather Service, convective-energy measurements from weather balloons and lightning-strike-occurrence data from the University at Albany.

“(The result) was much better than we had imagined it to be,” Romps said. “That’s what gave us the confidence to look at these climate models and find out what the product of these two features is going to be doing in the future.”

Lightning strikes in the contiguous United States are expected, on average, to increase 12 percent per degree Celsius of global warming, the paper found.

Jacob Seeley, a doctoral candidate who works with Romps, remembered asking him why no one had yet to fall on such a simple relationship. The difference seems to be in the area examined: Analysis of lightning happens mostly on a small scale, but Romps and his colleagues averaged data from throughout the United States.

Ronald Cohen, director of the Berkeley Atmospheric Science Center, praised the research. Predicting lightning is a popular objective, and the most widely used predictor of lightning in climate models involves multiplying a constant by the maximum cloud height to the fifth power, according to the paper.

”What David and his student did together was to find something much simpler and more elegant and more likely to be correct,” Cohen said.

Lightning strikes cause an average of 24,600 fires a year, amounting to $407 million in damages in the United States alone, according to the National Weather Service.

Ozone — a potent greenhouse gas — is also a byproduct of lightning, and more ozone might lead to what Cohen calls a “positive feedback” in the greenhouse gas cycle, whereby more gas leads to a warmer climate and therefore more lightning strikes.

Romps hopes to next extend the metric to mapped predictions of lightning-strike occurrences in the United States.

Contact Philip Cerles at [email protected] and follow him on Twitter @PhilipCerles_DC.