Weather Tied to Decline of Smog

Midway into the summer smog season, the county has been spared heavy smog, continuing a trend that is gradually bringing clean air back to Ventura County.

But because one day this summer exceeded a federal one-hour ozone limit, it postpones for at least another year the county’s ability to meet a standard set by the nation’s Clean Air Act.

Under the goal set by clean air regulations, Ventura County can exceed the standard only three times in a three-year period. Last year, the county exceeded it once. The year before, it exceeded it twice.

“It looks like we’ll get it before deadline” in 2005, Dick Baldwin, the county’s air pollution control officer, said Friday. But, “weather’s always an overriding factor.”

And still ahead in the May-to-October smog season could come the hot and stagnant weather that typically brings the worst air pollution of the year, local air quality officials say.

In the past two years around this time, smog watchers were hoping heavy smog would stay away all season, but they were disappointed when hot days struck later.

But temperatures this summer are running several degrees cooler than normal, thanks to cool ocean currents and off-shore breezes, said Bruce Rockwell, a meteorologist with the National Weather Service office in Oxnard. But that has been broken up by an occasional heat wave, he said.

“Every two or three weeks we normally get it. This year, it’s about once a month,” he said. “The overwhelming factor is the cooler water off the shore.”

Since El Nino in 1997, Ventura County has consistently dodged the high smog levels that it once regularly experienced.

Nonetheless, the county counted 12 violations of more stringent federal eight-hour standards, with Simi Valley included in nine of those. Those numbers may sound high, but the frequency is down about 80% from 10 years ago, according to the county Air Pollution Control District.

Thanks to more stringent regulations, industry cleanup efforts and new technologies, smog appears to be declining in Southern California.

Mallory Ham, a meteorologist with the district, said this year was slightly smoggier than last year. The cooler air and breezes have kept the county relatively smog-free.

Weather plays a key role in smog formation. When fumes from tailpipes and smokestacks mix with sunlight, ozone--a toxic, invisible gas--is formed. Warm, stagnant air acts like a lid, keeping the pollutants pressed low over cities. Cooler, breezier air forces it to dissipate.

“We have had some smoggy days,” just not to the extent of the past, Ham said.

“We’ve been in a system where we haven’t seen the high pressure over Southern California. We’re extremely low for this time of year.”