In Salt Lake City each winter, the “inversion season” happens, where for weeks at a time between storms, the air turns brown with smog. The normally beautiful views and landscapes become hidden by fog and haze, and the mountains only a few miles away cannot be seen. I have always wondered why this is a common occurrence here in Salt Lake City but not in other major cities, and whether we can do anything to improve the problem.
According to latimes.com, in the Salt Lake City region, “weather and geography combine to set a trap for bad air.” In winter, the mountains trap pollution-filled cold air. In addition, when there is high pressure, a “lid” of warm air forms on top of the dirty, cold air, keeping the pollution in the valleys. It only goes away when a low-pressure storm system moves in, removing the lid and blowing away the emissions.
According to ci.slc.ut.us, the main cause of pollution is PM 2.5, or fine particulates (particles smaller than 2.5 micrometers in diameter). Industrial processes contribute about 11% of the wintertime PM2.5, but a majority of our pollution comes from cars and wood burning. This means the two best ways to reduce pollution are to reduce driving and wood burning during inversions.