The Hazy Days of Summer : Fog, Smog Season Returns

The dingy days of early summer have arrived in eastern Ventura County, with coastal morning fog giving way to afternoon smog that often creates a daylong haze.

Air pollution, worse in Simi Valley than anywhere else in the county, is forecast to reach into the unhealthy range there over the weekend, said Kent Field, meteorologist with the Ventura County Air Pollution Control District.

The air in Thousand Oaks is expected to be moderately smoggy, but should not reach unhealthy levels.

“That dingy haze out there is both smog and the marine layer,” Field said. “We came within one part per billion of exceeding the federal standard for air quality earlier this week. And that means the air is unhealthy.”

Air quality along the coast has been hovering in the moderate range, neither good nor unhealthy. Residents there are seeing the typical foggy days of June, which will probably persist through mid-July.

“June Gloom is certainly an accurate term for it,” said Vladimir Ryshko, National Weather Service meteorologist in Oxnard, referring to the local nickname for the foggy summer. “It looks like it will be that way for the foreseeable future.”

Indeed, the first day of June brought fog and mist for motorists.

The typical weather pattern that causes both air pollution and foggy days occurs when the deserts to the east of Ventura County heat up. The warm air rises and creates low-pressure pockets below.

At the same time, out at sea, a strong high-pressure system moves closer to the coast, carrying cool, moist air from the ocean.

As the ocean air is drawn east, so are the pollutants created throughout the entire west end of the county, Field said.

Once the pollutants reach Simi Valley, they bump up against the hills behind the valley, creating a pocket where they are baked into ozone. Ozone, the primary component of smog, is harmful to lungs and can cause other health problems.

Although ozone is a colorless gas, other components of smog are not. Gasoline molecules that are not completely burned add color to the smoggy haze, as do nitrogen oxides, both of which are produced by motor vehicles.

County air pollution officials are trying to track how the pollutants move from west to east with a federally funded, $1-million program.

Through the program, the air pollution district installs chrome canisters at two locations at Rio Mesa High School in Oxnard and Simi Valley High School in Simi Valley.

The canisters have tubes that suck air into them over a three-hour period. They are then taken to the district’s laboratory in Ventura, where the gases and pollutants are analyzed. The canisters were brought out Thursday for the first time this season.

“We want to see if some of the things we see in the air in Oxnard are being carried out to Simi Valley,” Field said. “Then we can look at reducing the pollutants over the years to make the air healthier for the people who live in Simi Valley.”

The National Weather Service’s 90-day forecast for the region calls for a slight chance of warmer than normal temperatures, Ryshko said.

“For a farmer, it would mean crops might mature a little faster,” he said. “Or large bodies of water might lose more to evaporation. But it won’t matter that much to most people.”

Except for the smog levels, which could grow higher with warmer temperatures. “We would not only see more days of [federal health standard] exceedence, we would also see higher concentrations of ozone,” Field said.