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Thermal inversion occurs when the air temperature, instead of descending as we go up in height as is normal, rises more and more.
Air cannot rise in an inversion zone, since it is colder and therefore more dense in the lower zone.
A thermal inversion can lead to air pollution, such as smog (polluting fog) or haze (presence in the atmosphere of very small suspended dust particles) being trapped near the ground, with harmful effects on health.
With thermal inversion, the smoke cannot rise and remains in the fog layer, thus increasing pollution. But, it is also a very spectacular phenomenon to see, as in these images captured for Las Fotos de los Lectores de La Vanguardia in Santa CecÃlia de Voltregà .
The fog was very dense in the valley of the River Ter, changeable. As a negative fact, we see in this accelerated video the smoke that cannot get out of the fog.
In another part of Catalonia, in the Urgell region, we see how the smoke is trapped in the clouds and cannot rise any higher.
These are images taken from the C14 road, at the height of the village of Altet, looking towards Villagrasa.
