A temperature inversion occurs when a layer of warmer air traps a layer of cooler air near the surface.
Temperature inversions are most common after clear cold nights, when the heat escapes up through a cloudless sky, leaving the ground and the air that touches it much colder than the air higher up.
Frosts are a sign that a temperature inversion is more likely.
Temperature inversions create a ‘sandwich effect’ and clouds, mist, smoke, sounds and light are affected.
It can smell smoky and sounds travel far. We will often see layers of mist, but there are stranger effects too. From The Walker’s Guide to Outdoor Clues & Signs:
“Light is refracted in an inversion, and this unusual bending of the rays leads to optical illusions. In normal atmospheric conditions, very distant objects appear shortened and squashed; this is why we often see a squashed fat sun at sunset. In an inversion the opposite happens and objects appear to be stretched vertically. This can lead to an optical illusion called a ‘Fata Morgana’, from the Italian nickname for this strange type of mirage. A Fata Morgana is best known for making objects appear to levitate in the distance: bridges and boats are seen to hover above the water. This type of inversion refraction effect will also improve your chances of seeing the rare phenomenon known as the ‘green flash’, when a momentary burst of green light is seen at the exact moment of sunset.” Learn more here.
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