Soil frost: origin and difference to air frost
Frost is not just frost. A distinction is made between air frost and ground frost. With the cold season, the frost also comes to our gardens. We clarify the difference.
Air frost and ground frost - the difference
Frost is generally the temperature that occurs below 0 ° Celsius. This is also the freezing point of water.
- One speaks of air frost when the air temperature, which is measured at a height of two meters above the ground, drops below 0 ° Celsius.
- Therefore, on a day when the minimum temperature is below 0 ° Celsius, one also speaks of a frost day.
- In order to be able to speak of ground frost, the temperature near the ground - usually measured at 5 cm above the natural ground - must be below freezing.
- If there is frost in the air, there is also a low floor temperature. Not only are the temperatures in the frost area at a height of 2 meters, but also the temperatures near the ground.
The formation of ground frost
In contrast to air frost, ground frost can also occur if the air temperature at two meters is still up to four degrees plus.
- This is because cold air is heavier than warm air and therefore sinks to the floor. For example, the air can still be above freezing at a height of two meters, but it can cool below zero degrees near the ground.
- This occurs especially on cold, windless nights.
- In addition, this phenomenon can also lead to slippery roads. If there is frost in the ground, e.g. B. by fallen rain, low ground frost temperatures freeze the wet, it creates slippery streets.
- Especially in the transition months, one should pay attention to the frost in the ground. The lowest temperatures measured at a height of 2 meters are often above freezing during these months and do not indicate frost.
- Ground frost can still occur near the ground.
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