Frost

Frost on the lawn

If you live in an area with a colder winter, surely you have gotten up some morning and all the plants were covered by a thin layer of white ice. This layer, which appears to be snow, is called Frost. It is a phenomenon of formation of small ice crystals that form crystalline figures. They tend to form around cars, on windows, and on plants when temperatures are very low at night. For frost to form, not only is it enough to have a low temperature, but other conditions have to be met for it to happen.

Do you want to know what the requirements are and how frost is formed? In this article we are going to explain everything to you in detail.

Air humidity saturation

Ice crystals

The air we breathe is not just a mixture of gases in which oxygen and nitrogen predominate. There are also moisture or what has been water in a state of vapor. As we know, the saturation of air in humidity depends on the temperature of the air mass and the environment. The lower the temperature, the sooner the air becomes saturated with humidity. This is what happens when we get to the car in winter and with our breathing we are causing the windows to fog up.

What happens when we enter this situation is that the air inside the car is cold, so if we are continuously exhaling air with humidity, we will be saturating it and it will end up condensing. To remove fogging from the windows, we must use the heating. Warmer air supports more water vapor without condensing.

Although it seems like something that goes against all logic, the air that exists in the desert has more water vapor than that in a snowy mountain area. What happens then? Well, the air mass with a higher temperature is capable of holding more water vapor without it condensing.. This is known as the dew point. and indicates the temperature from which the air becomes saturated with humidity and begins to condense. The same goes for the mist we emit on cold winter nights.

How frost forms

Frost on cars

Once we know the saturation point of the air in humidity, we can understand how frost forms. Well, since the air we breathe contains moisture, if the temperature is too low, the water vapor will not only condense, it will turn into a solid state. For frost to form, there must be a temperature lower than that of the saturation point of the air.

When night falls, the sun stops providing heat to the environment and the air begins to cool rapidly. The earth cools even faster than the air does. If there is no wind, the air cools down in layers. The air that is colder, is denser, so it descends to the surface. On the other hand, the warmer air will remain at higher elevations, since it is less dense.

When the cold air mass descends to the surface, the temperature will drop further due to the effect of cold between the air mass and the colder land. This will make the temperature lower than the humidity saturation point of the air, so the water vapor condenses into water droplets. If the ambient temperature is less than 0 degrees and there is no wind to destroy that stability, the water droplets deposited on surfaces such as plant leaves, car windows, etc. They will turn into ice crystals.

This is how frost takes place on cold winter nights.

Requirements for frost to form

Frost on plants

As we have seen, we need the air to be below zero degrees, without wind and for the air to be saturated with humidity. In climates where the air is dry, you won't see frost build up even if the temperature is -20 degrees or less. The fact that water freezes to zero degrees is not entirely true. We have been taught since childhood that the freezing point of water is zero degrees, but this is not the case at all.

Natural water usually has impurities such as dust, specks of earth or any other substance that acts as a nucleus for hygroscopic condensation. This means that these particles act as a nucleus for the formation of water droplets or, in this case, ice crystals. If the water were completely pure, without any condensation nuclei, a temperature of -42 degrees would be needed for the water to change from a liquid to a solid state.

This is also one of the reasons why in some places with high atmospheric dust there are stronger and unexpected rains. This is because there is a higher concentration of condensation nuclei forming the clouds and the drops of water are formed before the precipitations.

These condensation nuclei can also be found on the surfaces that we have mentioned, such as cars, glass or water that is evapotranspires through the gas exchange of plants. The surface of the plant may also have specks of dust, sand, etc. That act as a condensation nucleus for the formation of ice crystals.

Negative consequences

Frost on trees

Frost itself is not dangerous depending on the surfaces where it is generated. If we have frost on the asphalt it can lead to a traffic accident due to a poor adaptation of the wheels to the ground and an unexpected skid. On the other hand, there are many crop plants that do not tolerate frost and less frost. In these types of situations, crops can be seriously affected.

For the rest of the surfaces, frost does not usually give problems. It simply increases the feeling of cold.

I hope this information helps you learn more about frost.


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