Today I want to talk about a phenomenon that I could see last night related to the entrance of very cold air and a lot of pressure.
As you know, Spain is “whipped” by an anticyclone that are only high pressures. I indicate the anticyclone because it is something important and it is referring to knowing that the atmosphere can be compared to a layer cake. Each of the layers of the atmosphere differs in the gases that compose it and in the density.
The density of an element is easy to explain. It is the amount of element per unit of volume, depending on the units, of course.
Now, as the density depends on the amount of mass between the volume it occupies, when there is something that “presses” the mass, like the pressure, there will be more in the same volume. As a summary and on the anticyclone, there is simply more density of “air” (with all its elements) than in a storm (which are low pressures).
Without entering what is an anticyclone except the push of the upper layers of the atmosphere towards “down” indicate that if we add a cold anticyclone (high pressures) we can have a very fun effect: frost on different levels.
The frost is easy to explain, it is nothing more than the water of the atmosphere in suspension that, by the cold, condenses.
When there is a high-pressure anticyclone (1035-1040 millibars, one unit), the cakes that make up the atmosphere are very well differentiated and if we combine the cold, there may be frost at different heights. That is, we can have “clean” air at ground level and frost on a layer greater than 15 meters.
This, at this time, is nice to see, since it is “snowing” above our heads but not where we are.
That is, clear pressure differences, coupled with high pressures and attached to “low” temperatures can give frost effect at different temperatures.
If this happens (usually) at night, thanks to the Earth, at night, or rather, when night falls, radiates the temperature it has, we will have an effect on the sky called white dew.
In this effect, layers above reflect the light and scatter it perfectly observing the difference between them.
Unfortunately I do not have any photos (I was driving and it was observed when crossing a car) but, for you to give you an idea, it is the typical effect that is observed in the games where you see “fog” at a certain height.