SAN FRANCISCO -- Atmospheric pollution from eastern Asia is beginning to have measurable, though still small, effects on air quality in western North America, a researcher from the University of Washington, Bothell, said today. Pollutants traceable to Asia include carbon monoxide, a direct byproduct of combustion; peroxyacetyl nitrate (PAN), indirectly caused by combustion; and particulates, said Dan Jaffe, an associate professor who studies atmospheric chemistry and air pollution.
Jaffe, along with UW research meteorologist Theodore Anderson, UW atmospheric sciences research professor David Covert and several other researchers, are presenting their findings this week during the fall meeting of the American Geophysical Union. The research was discussed at a news conference today, and Jaffe also is coordinating panel presentations on the transportation of pollutants and dust across the Pacific and Atlantic oceans.
The scientists found that Asian pollution travels to North America in the troposphere, at a maximum altitude of about 10,000 feet, when meteorological conditions are just right. 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, act like twin gears pulling a high-speed conveyor belt laden with Asian air directly across the Pacific Ocean. On average the air reaches the West Coast in about seven days, but it can take as few as four and as many as 10.
"What we know for sure is that we see pollutants coming from Asia under certain specific conditions," Jaffe said.
In some instances, such as a major Gobi Desert dust storm earlier this year, pollution from Asia could have health implications on the West Coast. Still, on days of high air pollution levels in metropolitan areas such as San Francisco, Seattle and Los Angeles, the Asian factor is very small, Jaffe said.
"We're still talking about a relatively small part of the pollution, but with the rapid industrial growth taking place in Asia we expect that the impacts will increase," he said.
The findings are part of a three-year project called the Photochemical Ozone Budget of the Eastern North Pacific Atmosphere, funded by the National Science Foundation.
Measurements taken on March 29, 1997, at the Cheeka Peak Observatory on Washington's northwest coast showed pollutant levels elevated substantially from what is typically found in marine air that has been cleansed as it crosses the Pacific. Several other instances of direct airflow from Asia during March and April 1997 also showed higher levels of the pollutants. However, the March 29 measurements came from air that was most clearly traceable to a large area of eastern Asia. Those readings showed carbon monoxide levels 10 percent higher than normal marine air, a nearly 100 percent rise in PAN, and a 50 percent increase in particulates.
"In this suite of measurements, we don't yet have enough data to say it's coal burning in China or an oil source in Tokyo. But we're moving in that direction," Jaffe said.
The measurements were repeated in March and April this year, but that data still is being analyzed. Readings will be taken in the same months next year using an NSF aircraft from the University of Wyoming.
A year ago, Jaffe's team reported the completion of a model to study the flow of pollutants from Asia. With one notable exception, actual measurements are confirming predictions from the model. Jaffe said the team has not seen significant ozone increases from Asia as expected, but he's not certain whether that is because of limited sampling or because the model needs to be adjusted.
For more information, Jaffe can be reached on Dec. 6 and 7 in San Francisco by leaving a message at the Best Western Canterbury Hotel, 415-474-6464, or through the AGU press room at 415-905-1007. Through Dec. 6 and starting the afternoon of Dec. 8, he can be reached at 425-352-5357 or by e-mail at email@example.com.