Air quality to deteriorate this week with new temperature inversion

SALT LAKE CITY — A brief respite from air pollution in northern Utah will come to an end this week as a new temperature inversion builds up, trapping more gunky air quality underneath warmer temperatures above the valleys. 

The Utah Division of Air Quality currently forecasts “moderate” conditions starting Tuesday, meaning that “unusually sensitive people” may want to reduce their time outdoors. Their website forecasts three days at a time, so the prediction for Wednesday and beyond is not yet available. 

However, without a new storm to stir up the air and push pollutants out, Sam Webber, a meteorologist with the National Weather Service in Salt Lake City, expected air quality to deteriorate further until the next storm arrives. 

“Certainly, having solid inversion conditions in place by Tuesday, likely persisting at least through Wednesday evening,” he said. 

The inversion does not create the pollution

A temperature inversion itself is a naturally occurring phenomenon common to areas with geography like that of northern Utah, where mountains frequently create a bowl shape around valleys. Normally, the higher up in the atmosphere you go, the cooler the air temperature is. But in an inversion, warm air traps cold air below. In northern Utah, that means temperatures are warmer at elevation than on the valley floor. 

When a temperature inversion moves in, it frequently traps pollutants in the air in addition to the colder air. Webber explained that this past weekend’s winter storm came with a low-pressure system; now, a high-pressure system has replaced it.

Air quality deteriorates during inversion

Webber expected the building high-pressure system the next few days to bring warmer temperatures overhead, trapping particulate pollution under the layer of warmer air. 

“With all this cold and areas of snow, particularly up in the Cache [Valley], moving into this next week, where we build this high-pressure, inversion conditions could become quite strong across the Wasatch Front,” Webber said. 

But relief could be swiftly behind that system. He expects another low-pressure system to move in by next weekend, pushing that pollution out and bringing more cold air with it. 

“Looks like it’s going to bring some pretty good relief from that inversion. Could see temperatures quite a bit colder … even some valley snow,” he added. 

The role of snow in air quality and inversion cycles

The state Division of Air Quality points out that a temperature inversion frequently follows a snowstorm, along with worsening air quality. 

“Utah inversions often occur after a snowstorm,” the division’s website states. “The snow cover makes the air colder near the ground, and the clear skies warm the upper atmosphere. If a high pressure system moves in, the gradual sinking of the warmer air acts as a cap over the cooler air, much like a lid over the valley bowl. The longer a high pressure system lasts, the longer and stronger the inversion.” 

In other words, frequent storms, while potentially frustrating for commuters, can help keep the air cleaner by keeping the inversion from sticking around too long. 

Read more: 

• How Utah schools keep kids safe during inversion season
• New air pollution law in Utah will keep many state employees home
• LISTEN: Utah Clean Energy on the Olympics and Utah’s air quality

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