Ozone from Asia is wafting across the Pacific on springtime winds and boosting the amount of the smog-producing gas found in the skies above the Western United States, researchers said in a study released Wednesday.
The study, published in the journal Nature, looks at a phenomenon that has puzzled scientists in the last decade: Ground-level ozone has dropped in cities thanks to tighter pollution controls; but it has risen in rural areas in the Western U.S., where there is little industry or automobile traffic.
The study, led by Owen R. Cooper, an atmospheric scientist at the University of Colorado, examined nearly 100,000 observations two to five miles above ground -- in a region known as the free troposphere -- gathered from aircraft, balloons and ground-based lasers.
It found that baseline ozone -- the amount of gas not produced by local vehicles and industries -- has increased in springtime months by 29% since 1984...MORE
- Margot Roosevelt
(Via LA Times)