What is Temperature Inversion?

by Kieran Berryman October 17, 2024

Have you ever seen smog linger over a city? Well, this can be caused by pollution that becomes trapped in the lowest level of the atmosphere, creating air quality and visibility problems. The common name for this mixture of pollutants is smog. But how does this pollution become trapped in the first place?

The lowest layer of Earth’s atmosphere is called the Troposphere, and it is where smog is created (UCSB). Usually, air cools as it ascends through the troposphere. However, sometimes, a layer of warm air can prevent this cool air from rising.

Temperature Inversions are what create the conditions for this to happen.

What is Temperature Inversion?

According to the Utah DEQ, "under normal atmospheric conditions, air is warmer near the ground and colder at higher altitudes. In a temperature inversion, the situation "inverts," and cold air at the surface gets trapped under a layer of warmer air." Given that particulates and other forms of pollution move with the flow of the air, this inversion prevents them from rising. When this occurs, all of the pollution contained in that cool pocket of air stagnates, and sometimes forms smog.

Three Types of Temperature Inversion

Given that an inversion is formed when warm air overlies cooler air, there are a lot of different phenomena that can result in inversions. Of course, some causes are more common than others. Below are some common types of temperature inversions:

Ground or Radiation Inversion is the most common type of inversion. This occurs on clear nights when the wind is relatively calm because "without cloud cover to insulate the Earth's lower atmosphere like a blanket... the air closest to the surface cools faster than the air above it" (ND Gov). Of course, this means that a layer of warm air forms over the surface level cool air, creating an inversion.

Frontal Inversions occur as a result of interactions between cold and warm front passages. During a cold front passage, warm air "is displaced upwards by a "wedge" of cold air." Vice versa, during a warm front, warm "air slides up and over the colder... air below" (ND Gov). Both of these interactions result in a temperature inversion.

Subsidence Inversions happen most frequently during the summer and autumn when "air... in the middle or upper levels of the atmosphere" sinks downward and becomes compressed. This compression "results in a warm, dry, stable layer of air" (ND Gov). This layer, of course, traps cooler air underneath, creating an inversion.

Effects of Temperature Inversion

Temperature inversion causes a couple of main effects related to visibility and air quality issues.

Visibility: Smog, as discussed above, is clearly visible to the naked eye. When an inversion forms and causes the creation of smog, visibility in the affected region drops. According to the National Park Service, smog "affects how far we can see. It also affects how well we are able to see the colors, forms, and textures of natural and historic vistas."

Air Quality often worsens during inversions because all of the pollutants that would normally ascend through the troposphere become trapped at surface level. This directly affects the quality of our air. According to the Utah DEQ, the pollutants that get caught up in inversions commonly originate from "vehicles, wood burning, area sources, and industry." Many of these sources generate particulate matter (PM). Of course, particle pollution has been linked to a number of health issues.

Want to learn more about PM? Click Here

Sources

Below is a list of sources used in this blog:

Note: This article was originally published 12/01/2022 and updated 10/17/2024.