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Hoar frost, also hoarfrost, radiation frost, or pruina, refers to white ice crystals deposited on the ground or loosely attached to exposed objects, such as wires or leaves. They form on cold, clear nights when conditions are such that heat radiates into outer space faster than it can be replaced from nearby warm objects or brought in by the wind.
- Hoarfrost
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- Hoarfrost
hoarfrost, deposit of ice crystals on objects exposed to the free air, such as grass blades, tree branches, or leaves. It is formed by direct condensation of water vapour to ice at temperatures below freezing and occurs when air is brought to its frost point by cooling.
21 de feb. de 2019 · Emilie Bonnevay. Public enquiries officer. Hoar frost is a type of feathery frost that forms as a result of specific climatic conditions. The word ‘hoar’ comes from old English and refers to the old age appearance of the frost: the way the ice crystals form makes it look like white hair or a beard. How does hoar frost form?
Frost crystals, often called hoarfrost in the aggregate, form when the invisible water vapour of the atmosphere passes into the ice crystal phase without going through the intermediate liquid phase. Hoarfrost lightly covers fields and rooftops under conditions that would form dew if the temperature were above freezing at the point of formation.
from Proto-Germanic – *hrīmaz, *hrīmą (“hoarfrost”) from Proto-Indo-European – *krey- (“to streak; graze; touch”). Hard rime Hard rime on trees in the Black Forest of Germany. Hard rime is a white ice that forms when the water droplets in fog freeze to the outer surfaces of objects.
hoarfrost. a deposit of interlocking ice crystals (hoar crystals) formed by direct sublimation on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc.; the surfaces of these objects are sufficiently cooled, mostly by nocturnal radiation, to cause the direct ...
