Inversions

Based on the inversion explanation on KSL television about a month ago, I understand why we get inversion in the winter (because of the cloud cover), but why do we also get it in the summer (since we don't get much cloud cover then)?

Do other areas of the country also get inversion, or is it just because we are in a mountainous area?

Thanks.

Michelle B.

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Great question and let's get straighten you out a bit. I don't know how cloud cover got into the explanation but inversions more or less are somewhat related to lack of cloud cover and high pressure.

The easy way to remember what happens with an inversion is to think about a typical day in your town. On a typical day in Salt Lake as we travel vertically (UP) through the atmosphere, the temperature is getting colder. You see this in the summer when you go up to hike Alta and it's nice and cool but it's blazing hot on the city. Temperature decreases with height.

On an inverted day we have the opposite going on, the temperature going UP above our heads is increasing! This problematic. When you have warm layer over a cold one, the cold air is sinking, it doesn't mix into the warm layer at all, it's trapped.

With high pressure we have an inverted temperature profile or an inversion as it's called. This means that there is a warm layer above the ground trapping the colder denser air. The air can't mix, so if you add pollution to it, it will just sit over us until the high pressure weakens or moves.

If this is still hard to understand you can do an experiment in your home with a few bottles, some food coloring and warm and cold water. There's a link on the right to the experiment, get a few towels in the event you spill some of the water.

Valleys also help to trap polluted air, so yes, having big mountains and then valleys around does make us more vulnerable to hazy conditions. The mountains create a natural barrier which can disturb the mixing process. During the summer months you can still get cooler air at the ground and warmer air higher up with an area of high pressure. When this happens, pollution will get trapped.

In the winter, the high pressure is stronger and you have even more DENSE cold air at the surface of the earth. The inversion is stronger usually than in the summertime. We also have the lake breeze in the summer and that helps to mix us a little bit at times.

High pressure happens all year, it's not just seasonal. The strength of the high does relate to the inversion strength. Highs are typically stronger and deeper in the winter.

Answered by KSL Meteorologist Dina Freedman.