Have you ever seen the clouds below you while hiking? The weather phenomenon called temperature inversion is responsible for clouds getting trapped in valleys and canyons, creating beautiful scenery to admire.

What is a temperature inversion?

In normal conditions, warm air is found in the boundary layer, closest to the ground, while cold air is found above it. To get the idea, think about when you hike in the mountain: it will usually be chillier at the summit. However, sometimes temperatures in the atmosphere increase with altitude and the inversion of conditions acts as a “cap”. Colder temperatures end up being retained underneath a layer of warmer temperatures.

This phenomenon has many different effects such as trapping pollutants, with possible adverse impacts on health, and even preventing thunderstorms. One of the impressive effects of temperature inversion is to make clouds just below the inversion  spread out and have a flat appearance. This event is commonly called a “cloud inversion”.

 

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How does a cloud inversion form?

When the sun goes down, the temperature of the ground decreases which cools down the air just above it. However, the air at the top stays warmer as it does not lose its heat as fast. If the night is long, the winds calm and the sky clear, the inversion will be stronger and last longer. It is when humidity is high enough in the boundary layer – the part of the atmosphere which is closest to the ground – that fog is formed and gets trapped under the inversion.

Temperature inversions are more common in winter since the nights are much longer at this period.

 

Watch this video of the Grand Canyon being filled with clouds due to a temperature inversion.

This event in the Grand Canyon, Arizona, is quite rare, usually happening once a year, but it has already happened twice since December 2014.