Ground frost refers to the various coverings of
ice
Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...
produced by the direct
deposition
Deposition may refer to:
* Deposition (law), taking testimony outside of court
* Deposition (politics), the removal of a person of authority from political power
* Deposition (university), a widespread initiation ritual for new students practiced f ...
of
water vapor on objects and trees, whose surfaces have a temperature below the
freezing point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
of water (0 °C, 32 °F).
Types
The three main types of ground frost are radiation frost (
hoar frost
Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) ...
), advection frost (
advection hoar frost) and evaporation frost. The latter is a rare type which occurs when surface moisture evaporates into drier air causing its temperature at the surface to fall at or under the freezing point of water.
Rime (both
soft and
hard) is technically not a type of ground frost.
Alternative definition
Ground frost may also refer to the condition when the temperature of the upper layer of the soil falls below the freezing point of water.
In England
From 1906 to 1960 the
Met Office practice was to base the number of days of ground frost on this criterion: a day with a minimum temperature reaching 30 °F (−1 °C), probably because 32 °F (0 °C) was not considered enough cold to cause damage to growing plants. Since 1961 the statistics have referred to the ''number of days with grass minimum temperature below 0°C''. Occasionally, the term ground frost can still be seen, but it means simply a minimum temperature below 0 °C.
See also
*
Frost
Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above- freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a ga ...
*
Frost (temperature)
Freezing, available onlinlibrary.wmo.int/ref> or frost occurs when the air temperature falls below the freezing point of water (0 °C, 32 °F, 273 K). This is usually measured at the height of 1.2 metres above the ground surface ...
References
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Snow or ice weather phenomena