Smug Smog

Fairbanks and Los Angeles. One a frontier town bordered by wilderness. One a sprawling megalopolis bordered by smaller megalopoli. Generally, these two don't have much in common, except when both violate the Environmental Protection Agency's standard for carbon monoxide in the air.

Fairbanks recently had a string of four violations when, over eight-hour periods, more than nine carbon monoxide molecules were measured among a million other molecules of gases that make up the downtown air. The EPA is considering putting Fairbanks on the "serious list" of carbon monoxide polluters. The only name currently on the list is Los Angeles, which raises a question: How do the 30,000 people or so in the city core of Fairbanks generate the same density of carbon monoxide as L.A.'s 3 million?

Both cities are similar in that they're surrounded by hills and mountains and both experience temperature inversions, where atmospheric quirks cause temperature to increase with elevation. But almost everything else about the inversions are different.

In Los Angeles, "subsidence" (also known as "overhead") inversions endure for days and weeks because of a near-constant high-pressure system over the ocean southwest of the city. The high-pressure system pushes down on atmospheric gases over the L.A. basin, and the compression of gas molecules causes heat. The resulting warm air layer, which forms about 2,000 feet above the city, acts as sort of a lid that holds down cooler, polluted air.

Geophysical Institute Associate Professor of Chemistry Richard Benner said that Fairbanks experiences one of the most severe inversions on the planet, rivaled only by those at the South Pole. In his thesis on carbon monoxide in Fairbanks, Geophysical Institute graduate student Dave Veazey explained that Alaska inversions are caused by three factors: clear skies that allow heat to escape, low solar radiation that doesn't allow the earth to be warmed much in the first place, and calm winds.

Alaska inversions are known as "radiative," and originate at the surface of the earth, where the layer of air adjacent to the ground becomes cooler than the air above it. Cloudless nights assure that the trace of heat the ground gives off (which could break up the inversion by stirring up the air) radiates up through the atmosphere after sunset. With no wind, the colder gas molecules near the ground don't move, and the air becomes stagnant, trapping gases such as carbon monoxide.

An important difference between Fairbanks and L.A.'s inversions is the size of the box that holds the foul air. Because the mixing zone of gases in L.A. is at about 2,000 feet, L.A.'s box is relatively huge compared to Fairbanks', where Benner has stood with his son downtown and pointed out car exhaust plumes that were held down by an invisible 10-foot ceiling of warm air. In a box that small, it doesn't take long for carbon monoxide levels to reach nine parts per million.

Inversions can have a lot of staying power in Fairbanks, as was seen around the turn of the year when clear skies, low solar radiation and weak winds persisted, and Fairbanks rung up four straight days of EPA violations.

According to Benner, when Fairbanks isn't capped by an inversion, the air is probably 100 times cleaner than air in L.A., which is polluted by a slew of other airborne chemicals in addition to carbon monoxide. He said Fairbanks is much easier on the lungs.

"Given the choice of breathing Fairbanks air for one year or L.A. air for one day, I'd take Fairbanks hands down," Benner said.