In the winter, air pollution can stay trapped in the valleys of the Wasatch Front until the wind picks up and blows it away. In the summer, ozone pollution can be a problem day after day even when the wind is blowing.
Unlike particulates, which can build up for weeks in a winter inversion, new ozone is created every day by a reaction between tailpipe emissions and sunlight. Erik Crosman, a researcher in the University of Utah’s Atmosopheric Sciences program, says the wind doesn’t make much difference to pollution levels on a hot summer day.
“The precursor pollutants are over a deep area and those winds are not coming from a long distance away," Crosman tells KUER. "They’re just local flows, so they’re not blowing in cleaner air. In the wintertime, our pollution is confined to near the surface and the air aloft is very clean.”
Ozone levels tend to get worse as the temperature rises. Over the past week, levels in Utah’s urban areas have exceeded the federal standard of 0.075 parts per million several times.
Dr. Erik Crosman's PowerPoint presentation on winter v. summer air pollution: Ozone v. PM 2.5