Frost (temperature)

The expression Frost ( German. derivation of freeze ) refers to the occurrence of temperatures below 0 ° C ( freezing point of water ), especially in the environment, which are mainly affected creatures, the water and the soil. The permafrost of winter leads to winter tranquility of nature.

Air frost and ground frost

Frost ( to distinguish the ground frost also called air frost) in the sense of Meteorology and Climatology prevails when the air temperature two meters ( meteorological standard of measurement, measurement in the air hut) to below freezing drops. A day on which the minimum temperature below zero degrees Celsius, it is called a cold day accordingly.

Ground frost means that the temperature drops near ground level (usually at 5 cm above the natural soil ) below freezing. Ground frost can already occur when the air temperature is two meters even at plus four degrees in clear, windless nights quite.

Soil that remains frozen throughout the year, is called permanent or permafrost.

In temperate latitudes following formulations for the description of the temperature are used.

• Light frost: 0 to -4 degrees Celsius
• Excessive frost: -4 to -10 degrees Celsius

In addition, there is also the name of a low frost: 0 to -2 ° Celsius. For days with severe frost is in the climatology - ambiguous, and not common in German-speaking - Definition Cold Day in use.

Frosts: Lingerie, early and late frost

Frost as a weather event can be marked as follows:

• Frost days, with temperature events below 0 ° C
• Ice days, where the temperature never rises above 0 ° C; the other days of frost is called freeze-thaw days

Sinking the temperature at 2 m height below 0 ° C ( meteorological measurement standard ) by nocturnal radiation under a cloudless sky and in sheltered positions, one speaks of night frost. Here is microclimatic events.

Frosts are characteristic of the winter season, which includes the common practice of meteorology in Central Europe the months of December, January and February but throughout the winter season (ie mid-October to mid-April) will regularly - can still frost events after the end of the phenological Winters ( thus, the onset of typical vegetation signs of full spring ) and even in the early and full autumn occur. This can compromise as early frost in the fall harvest fruits (potatoes, sugar beet) or as a late spring frost damage in orchards, vineyards and horticulture. The ability of a plant to withstand such severe frost, called frost hardiness.

Permafrost

The winter frost can take depending on the region a few days or several months. In nature it leads to hibernation or dormancy, has direct influence on the dormancy of seeds and triggers the lap inhibition of crops by vernalization.

Among other things for road surfaces, it is especially harmful when the temperatures fluctuate over time around the freezing point and it is also humid. The change between freeze and thaw means that water gets into tiny cracks and freezes there. Ice has a lower density than water, so needs more space. It expands the barely visible columns with enormous power from a little so that the next time a little more water fits into it. After many repetitions occur as visible damage, it comes to frost weathering. Frost also leads to unprotected water pipes to a water pipe with the following water damage.

Frost in the maritime

In the maritime field, the terms White Frost ( Frost White English ) and Black Frost ( Black Frost ) icing of the ship superstructures. White frost is formed from the spray coming over sea (salt water) in heavy storm, Black Frost is formed from fog or drizzle (fresh water). Both can lead to capsize the ship and overload the rigging.

Frost warning

For different areas, particularly the agriculture and construction industry, it is important to know in advance whether it will come to the formation of frost. For this reason, a frost warning is issued if frost is likely. The decisive factor here is the minimum nighttime, for example, which is calculated in advance on the Taupunktregel. Here are three different levels, which are symbolized by stars:

• No night frost (*)
• Night frost possible (* )
• Night frost likely (** )

In agriculture, a blanket of snow provides the best frost protection in crop cultivation, late frosts in the spring, the frost protection irrigation is to protect sensitive crops spread applied.