As many of us have experienced, atmospheric temperatures typically drop as altitude increases above the Earth’s surface. During an event known as a temperature inversion, though, the exact opposite occurs.

The figure of 9.8°C per 1 000 metres is the dry adiabatic lapse rate, not the average rate at which atmospheric temperature normally decreases with altitude. The average environmental lapse rate is closer to 6.5°C per 1 000 metres. “Have experienced” is also grammatically correct here.

There is a phenomenon, however, that turns this norm on its head by causing an increase in temperature with height. It is called a temperature inversion.

We take a closer look at what a temperature inversion is, what causes it, and its impact on the weather and environment.

From the introduction alone, one should already have a pretty good idea of what a temperature inversion is. But before delving into the details of how it forms and the different types, one needs a clear and concise definition of what exactly temperature inversion is.

Temperature Inversion Definition​​​​​​​​​

A temperature inversion can be defined as a meteorological phenomenon that occurs when temperatures rise as altitude increases within a layer of air. This contrasts with the atmosphere’s typical behaviour, in which temperatures usually decrease as altitude increases.

This phenomenon can occur in a fixed position like the stratosphere, where the temperature naturally rises with height.

(The average temperature in the stratosphere starts at -51° Celsius or -60° Fahrenheit above the troposphere and rises to an average of -15° Celsius or 5° Fahrenheit  close to the mesosphere.)

Temperature inversion also takes place in pockets or layers of air throughout the atmosphere, caused by different variables. These layers are not so easily predictable and can have a dramatic impact on the weather and environment.

This section will focus on the different variables that cause the inversion layers that appear randomly throughout the atmosphere. Temperature inversion is primarily caused by four different factors, resulting in four types of inversion:

This form of temperature inversion usually takes place on a cloudless night with little or no wind present, creating the perfect conditions for heat to escape rapidly from the surface.

As a result, the air at the surface cools down much more quickly than the air above it in the atmosphere, creating a low-lying temperature inversion.

Colder air is denser than warmer air, so an advancing cold air mass tends to move beneath the warmer air and force it upward.

When the two fronts meet, the lighter and warmer air from the warm front is lifted up by the cold and dense air from the cold front, resulting in warm air on top of a layer of cold air.

Unlike a surface inversion, a frontal inversion develops higher in the atmosphere, where warmer air rises over the denser cold air along the boundary between the two air masses.

To find out more about warm and cold fronts and their characteristics, read more about them in this article.

This form of temperature inversion develops when large masses of air descend under high-pressure conditions. As the air sinks, increasing atmospheric pressure compresses and warms it.

This process also reduces the normal rate at which temperature decreases with altitude, known as the lapse rate. Because the upper part of the descending layer warms more than the lower part, warmer air can develop above cooler air closer to the surface, creating a subsidence inversion.

The topography of the surface can also be responsible for the creation of a temperature inversion. A good example of this form of inversion is the one that takes place at night in the valley between hills or mountains.

When it cools down in the evening, the surfaces of hillsides and mountain slopes cool more quickly than their surroundings, causing the air above them to cool. The colder air then moves down the slopes and accumulates at the bottom of the valley.

As the colder air moves into the valley, it lifts the warmer air at the bottom up and away from the surface. This leaves the valley with colder air at the surface and warmer air higher up in the atmosphere.

Due to the “unnatural” nature of temperature inversion, some unexpected and extreme conditions are created as a result of this phenomenon. Some of these results can be seen as potentially harmful and dangerous. The most important ones are:

Under normal conditions, when ice crystals combine to form snowflakes in subzero temperatures, they fall to the ground and stay intact as they pass through colder air near the surface.

With an inversion layer present, though, the snow melts as it falls through the warmer air. When the resulting raindrops exit the layer, they do not have enough time to freeze again, but their temperature continues to drop below freezing point, creating supercooled water.

This is called freezing rain, and as soon as these cold raindrops hit the surface, they are immediately turned into ice. This is extremely dangerous, as the thin layer of ice that is formed is almost invisible and extremely slippery.

When this ice forms on the surface of roads or pavements where people walk, it makes these surfaces very slippery and almost impossible to spot. This is referred to as black ice and is a major cause of accidents on and off the road in countries frequently experiencing this weather phenomenon.

(Learn more about freezing rain and how it differs from sleet in this article.)

A temperature inversion can also make sounds below it seem louder. It acts like a giant reflective ceiling, refracting sound waves back towards the ground.

This means sounds can travel further and sound much louder than they really are. For example, it has been extensively reported that thunderstorms sound much louder when an inversion layer is present.

Man-made sounds, such as those produced by passenger aircraft and explosions, can also sound louder and be heard further away.

Due to the infrastructure and the heat generated by transport and other human activities in a city, heat is absorbed and maintained, only to be slowly released in the atmosphere above the city at night and during cold winter months.

When a temperature inversion forms over the city, it acts as a seal that traps smog and other toxic emissions close to the surface.

This not only creates a serious environmental problem but also poses a dangerous and potentially life-threatening situation by keeping these gases trapped near the surface and in the lower atmosphere.

This not only creates a serious environmental problem but also poses a dangerous and potentially life-threatening situation by keeping these gases trapped near the surface and in the lower atmosphere.

You can read all about the Urban Heat Island effect, what causes it, and its effect on the weather and environment in this article. 

After reading this post, you will have a much better understanding of what a temperature inversion is and how it bucks the trend of normal atmospheric conditions.

To be honest, though, as the effects of long-term human-driven climate change become more apparent in weather patterns worldwide, a temperature inversion may no longer seem quite as rebellious or unexpected.

For now, one needs to understand the causes and dangers of temperature inversion so that its effects can be anticipated and the risks it creates can be reduced.

Until next time, keep your eye on the weather!