City skylines are often marked by haze and smog – in addition to sometimes sweltering temperatures during the summer months.
A professor at James Madison University has found an interesting connection between those conditions and thunderstorms.
Mace Bentley has been studying lightning in city environments for more than 20 years. He says cities are often hotspots for lightning – both for the urban center themselves and areas further downstream.
Urban heat islands contribute to that, but he and his team wondered if there might be more to the puzzle.
So, they looked at aerosols – think vehicle emissions or dust from construction sites. Here’s Bentley talking about aerosol optical depth – essentially the amount of haze on any given day.
“And we found very strong correlations between aerosol optical depth and lightning flash activity. And that was uniform across Kansas City or Washington D.C," Bentley says. "Aerosol optical depth is not as closely tied to the size of the particulate matter – it’s more closely tied to how much.”
Bentley has looked at several cities for his research over the years, including Atlanta, D.C. and Bangkok, Thailand. That included a recent comparison between D.C and Kansas City, Missouri to see if there were differences in the kinds of pollution present in the air when it comes to lightning strikes.
He stresses that aerosols don’t cause thunderstorms, but rather can augment them. And too much pollution can actually stymie storm development because it blocks out the sun – a necessary ingredient.
Bentley and his team also found differences by the day, too.
“There’s a lot of pollution that will build up right at the ground level, but it takes a few days for that to kind of start moving up into the atmosphere," he says. "Generally speaking, later in the week are the days when you’d expect thunderstorms to produce more flashes.”
He says cities should focus on adding green spaces and minimizing pollution through electric vehicles and better public transportation systems to help.
