To gather this year's data, Jaffe's team used a University of Wyoming plane that is part of a fleet of research aircraft operated by the National Science Foundation. The plane was outfitted with essentially the same equipment used at Cheeka Peak. On 14 flights between March 15 and April 28, the plane gathered data from several equally spaced levels between 1,500 feet (the same elevation as Cheeka Peak) and 23,000 feet. Pollution layers were observed on about one-third of the flights.
"This was a day when we could really see haze layers out there," Jaffe said of the April 9 flight.
Other scientists involved in the research are from the UW, Seattle; the University of California, Irvine; the National Oceanic and Atmospheric Administration; and the Atmospheric Environment Service of Canada.
Jaffe's previous research has shown that Asian pollution travels to North America when meteorological conditions over the Pacific are just right, typically during the spring. A low-pressure system over the Aleutian Islands and a high-pressure cell near Hawaii, which remain stable and in place for at least several days, work in concert to quickly move air from East Asia directly across the ocean to North America. The process, which the researchers have dubbed "The Asian Express," takes four to 10 days, too little time for the air to be cleansed over the ocean.
"For us to see what we're seeing, I think we have to be talking about a fairly large region of pollutants that remain intact and get transported across in one big blob," Jaffe said.