Afraid of thunder and lightning? Go live in the country because cities intensify summer thunderstorms, a new study suggests.
Researchers at Princeton University consulted models and observations of an extreme thunderstorm that hit Baltimore in July 2004 and found that about 30 percent more rainfall occurred in the city than would have if there were no buildings where the city now sits.
During the storm, Baltimore experienced as many lightning strikes in the space of two hours as the city normally sees in a whole year, with much of the lightning striking the western edges of the city.
"It's as if all of a sudden the lightning can 'feel' the city," said Princeton graduate student and study author Alexandros Ntelekos.
The researchers said there are three reasons a city thunderstorms are more intense. First, cities generate more heat than surrounding land, which could provide fuel to a storm. Second, Tall buildings can create wind drag, upward-moving air that increase rainfall. And third, Ntlekos and Smith discovered tiny air-suspended particles from vehicles and industry may have increased rainfall in the Baltimore storm.
This apparent interaction between storm and city has critical consequences for city dwellers and policymakers, especially in light of the likelihood of such fierce storms becoming more common with the influence of global warming (warmer air holds more water, which means more intense rainfall in any given storm).
"This means that warm-season thunderstorm systems will probably increasingly lead to more flash flooding, which can be very dangerous," said study co-author James Smith, also of Princeton.
The crippling effects of a severe thunderstorm in an urban area were felt in New York City last week as 2.5 inches of rain fell in three hours, flooding subway tunnels and causing major disruptions to the morning commute. A tornado also formed in Brooklyn, causing significant damage to property.
Source:Xinhua/agencies
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