They quantified the contribution of Asian pollution to surface ozone levels in both densely populated regions such as the Los Angeles area and rural areas such as national parks. They find that Asian pollution contributes as much as 20 percent of total ozone during springtime pollution episodes in western U.S. surface air.
Current guidelines from the Environmental Protection Agency dictate that, averaging over 8 hours, surface level air should have no more than 75 parts per billion per hour by volume of ozone. Although local pollution plays a large role on days when that standard is not met in Southern California, the authors estimate that 53 percent of the instances where that limit was exceeded would not have occurred without the contribution from Asian air pollution.
The researchers also find that an index based on satellite observations of Asian pollution plumes could serve as a qualitative early warning indicator, with a lead time of one to three days, of Asian pollution influence on western U.S. air quality.
Source: Journal of Geophysical Research-Atmospheres, doi:10.1029/2011JD016961, 2012 http://dx.doi.org/10.1029/2011JD016961
Title: Transport of Asian ozone pollution into surface air over the western United States in spring
Authors: Meiyun Lin: Atmospheric and Oceanic Sciences, Princeton University, Princeton, New Jersey, USA, and NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA;
Arlene M. Fiore: NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA, now at Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA;
Larry W. Horowitz: NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA;
Owen R. Cooper: Cooperative Institute for
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American Geophysical Union