The College Park team isn't interested in measuring common, ground-hugging smog. They're looking for pollution higher up, especially huge pancake-shaped clouds of pollutants called plumes. During heat waves, relatively warm layers of pollution-saturated air get trapped between cooler layers. This happens as the lower atmosphere gets warmer in the daytime and then cools at night. While some plumes form in this region, others float here from the west.
Scientists think they come from cities, power plants and factories in the Midwest.
Not all meteorologists factor these plumes into the equation when they make ozone forecasts. That can lead to faulty predictions, says Doddridge, an atmospheric chemist with UMCP's Department of Meteorology. In equipping their chartered Cessna, the team has installed two pencil-sized tubes, one made of Teflon and the other of stainless steel, in the leading edge of the port wing. Both act as miniature vacuum cleaner nozzles, sucking up the dirty air outside. The tubes lead to two suitcase-sized blue boxes strapped to the back seat with white nylon rope.