Dear Tom,
Were there any weather changes following the cessation of jet traffic on 9/11/2001?
Leo Goshen
Dear Leo,
All commercial aircraft across the United States and Canada were grounded for three days following the terrorist attacks of Sept. 11, 2001.
That constituted a gigantic unplanned weather experiment, one consequence of which was a demonstration that high-altitude jet condensation trails affect surface temperatures. Water vapor in jet exhaust condenses into a thin veil of ice-crystal clouds that lowers daytime and raises nighttime temperatures slightly in very high-traffic jet corridors.
In the absence of those clouds during the three days of grounded jet traffic, the spread between daily high and low temperatures increased by 2 (degrees) F.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
