Dictionary: frost   (frôst, frŏst)

1. A deposit of minute ice crystals formed when water vapor condenses at a temperature below freezing.
2. A temperature low enough to cause freezing.
3. The process of freezing.
4. A cold or icy manner.

1. To cover with frost.
2. To damage or kill by frost.
3. To cover (glass, for example) with a roughened or speckled decorative surface.
4. To cover or decorate with icing: frost a cake.
5. Slang. To anger or upset: What really frosted me about the incident was the fact that you lied.

To become covered with or as if with frost.

[Middle English, from Old English.]

A covering of ice in one of several forms produced by the freezing of supercooled water droplets on objects colder than 32°F (0°C). The partial or complete killing of vegetation, by freezing or by temperatures somewhat above freezing for certain sensitive plants, also is called frost. Air temperatures below 32°F (0°C) sometimes are reported as “degrees of frost”; thus, 10°F (−12°C) is 22 degrees of frost (this usage is confined to the Fahrenheit scale and is not applied to Celsius temperatures).

Frost forms in exactly the same manner as dew except that the individual droplets that condense in the air a fraction of an inch from a subfreezing object are themselves supercooled, that is, colder than 32°F (0°C). When the droplets touch the cold object, they freeze immediately into individual crystals. When additional droplets freeze as soon as the previous ones are frozen, and hence are still close to the melting point because all the heat of fusion has not been dissipated, amorphous frost or rime results.

At more rapid rates of condensation, the drops form a thin layer of liquid before freezing, and glaze or glazed frost (“window ice” on house windows, “clear ice” on aircraft) generally follows. Glaze formation on plants, buildings and other structures, and especially on wires sometimes is called an ice storm, a silver frost storm, or thaw.

At slower deposition rates, such that each crystal cools well below the melting point before the next joins it, true crystalline or hoar frosts form. These include fernlike assemblages on snow surfaces, called surface hoar; similar feathery plumes in cold buildings, caves, and crevasses, called depth hoar; and the common window frost or ice flowers on house windows.

Killing frosts or freezes damage or kill vegetation depending on their duration and their intensity, that is, how far the plant temperatures go below 32°F (0°C). Such conditions result from advection of much colder air, which then cools the plants, as in the infamous cold waves of the north-central United States; or from radiational cooling of the plants themselves, by long-wave radiation to clear skies at night. In either case, the extent to which plant fluids freeze determines the severity of the frost. See also Air temperature; Dew; Dew point.

1. In cooking, frost means to cover and decorate a cake with a frosting or icing. 2. To chill a glass in the freezer until it's frosted with a thin coating of ice crystals.

Definition: extreme cold
Antonyms: heat, hot, warm

Frozen dew or fog forming at, or near ground level. Black frost, as the name suggests, is a thin sheet of frost without the white colour usually associated with frost.

Air below 0 °C is air frost. Hoar frost, or rime, is a thick coating of white ice crystals on vegetation and other surfaces. Ground frost occurs when the air at ground level is chilled below freezing point.

Frost hazard on roads is most common in maritime climates, such as in Scandinavia and the British Isles, where rainfall is regular and winter temperatures oscillate unpredictably around 0 °C, and while salt is an effective de-icing agent it damages both road surfaces and vehicle bodies. Frost is also an agricultural hazard; in 1971 the annual frost loss in the USA was estimated at $1.1 billion. Measures such as direct heating of orchards with oil burners and the use of wind machines may prevent frost damage. The most effective response, however, is the choice of a frost-free site. See frost pocket.

For more information on frost, visit Britannica.com.

The action (or result of such action) of the freezing of water vapor on a surface (e.g., the ground) that is colder than 32°F (0°C).

1. a deposit of frozen dew.
2. a deposit resembling frozen dew or vapor.

• f. (1) studs — large-headed horseshoe nails that protrude below the horseshoe, or special studs fitted to the shoe itself, that give better grip on the ice. Called also calks, calkins, cogs.
• urea f. (2) — the appearance on the skin of salt crystals left by evaporation of the sweat in urhidrosis.

Frost on black pipes

Frost is a solid deposition of water vapor from saturated air.

Formation

If solid surfaces in contact with the air are chilled below the deposition point (see frost point), then spicules of ice grow out from the solid surface. The size of the crystals depends on time and the amount of water vapor available.

Frost is often observed around cracks in wooden sidewalks due to the moist air escaping from the ground below. Other objects on which frost develops are those with low specific heat and high thermal emissivity, such as blackened metals; hence the accumulation of frost on the heads of rusty nails. The apparently erratic occurrence of frost in adjacent localities is due partly to differences of elevation, the lower areas becoming colder on calm nights. It is also affected by differences in absorptivity and specific heat of the ground which in the absence of wind greatly influences the temperature attained by the superincumbent air.

Because cold air is more dense than warm air, in calm weather cold air pools at ground level. This is known as surface temperature inversion. It explains why frost is more common and extensive in low-lying areas. Areas where frost forms due to cold air trapped against the ground or against a solid barrier such as a wall are known as "frost pockets".

Frost is similar in appearance to soft rime, but the two are distinct. In formation of frost, the water vapour condenses through deposition directly to solid ice whereas rime is formed following initial condensation into liquid droplets. Thus, frost is formed when the dew point is warmer than surface but colder than the air temperature, and colder than freezing point. The formation of frost is an example of meteorological deposition.

Types of frost

Radiation frost (also called hoar frost or, sometimes, hoarfrost) refers to the white ice crystals, loosely deposited on the ground or exposed objects, that form when the air is moist, the wind is weak or absent and surfaces are cold. It is often seen on clear winter nights, especially in valleys and hollows. Hoar frost can form in these areas even when the reported temperature is above the freezing point of water

One can distinguish between some types of hoar frost, depending on where it forms. For example, air hoar is a deposit of hoar frost on objects above the surface, such as tree branches, plant stems, wires; surface hoar is formed by fernlike ice crystals directly deposited on snow, ice or already frozen surfaces; crevasse hoar consists in crystals that form in glacial crevasses where water vapour can accumulate under calm weather conditions; depth hoar refers to cup shaped, faceted crystals formed within dry snow, beneath the surface.

Depth hoar is a common cause of avalanches when it forms in air spaces within snow, especially below a snow crust, and subsequent layers of snow fall on top of it. The layer of depth hoar consists of angular crystals that do not bond well to each other or other layers of snow, causing upper layers to slide off under the right conditions, especially when upper layers are well bonded within themselves, as is the case in a slab avalanche.

Hoar frost does not occur exclusively in nature. Hoar frost is also found in and around freezers particularly in industrial cold storage facilities. It occurs in adjacent rooms that are not well insulated against the cold and around entry locations where humidity and moisture will enter and freeze instantly depending on the freezer temperature.

White frost is a relatively heavy coating of hoar frost with big and interlocking crystals. It forms when the air has a relative humidity above 90% and a temperature below -8 °C (18 °F).

Advection frost (also called wind frost) refers to tiny ice spikes forming when there is a very cold wind blowing over branches of trees, poles and other surfaces. It looks like rimming the edge of flowers and leaves and usually it forms against the direction of the wind. It can occur at any hour of day and night.

Window frost (also called fern frost) forms when a glass pane is exposed to very cold air on the outside and moderately moist air on the inside. If the pane is not a good insulator (such as a single pane window), water vapour condenses on the glass forming patterns. The glass surface influences the shape of crystals, so imperfections, scratches or dust can modify the way ice nucleates. If, otherwise, indoor is very humid water would first condense in small droplets and then freeze into clear ice.

Frost flowers occur when there is a freezing weather condition but the ground is not already frozen. The water contained in the plant stem expands and causes long cracks along. Water, via capillary action, goes out from the cracks and freezes on contact with the air.

Effect on plants

Hoar frost on a rose.

Many plants can be damaged or killed by freezing temperatures or frost. This will vary with the type of plant and tissue exposed to low temperatures.

Tender plants, like tomatoes, die when they are exposed to frost. Hardy plants, like radish, tolerate lower temperatures. Perennials, such as the hosta plant, die back after first frosts and regrow when spring arrives. The entire visible plant may completely turn brown until the spring warmth, or will drop all of its leaves and flowers, leaving the stem and stalk only. Evergreen plants, such as pine trees, will withstand frost although all or most growth stops.

Vegetation will not necessarily be damaged when leaf temperatures drop below the freezing point of their cell contents. In the absence of a site nucleating the formation of ice crystals, the leaves remain in a supercooled liquid state, safely reaching temperatures of -4 °C to -12 °C. However, once frost forms, the leaf cells may be damaged by sharp ice crystals. Certain bacteria are particularly effective at triggering frost formation, raising the nucleation temperature to about -2 °C. In the absence of these "ice-nucleating" bacteria, frost damage can be greatly reduced ^[1].

The Selective Inverted Sink ^[2] prevents frost by drawing cold air from the ground and blowing it up through a chimney. It was originally developed to prevent frost damage to citrus fruits in Uruguay.

See also

Wikimedia Commons has media related to:

Hoar frost

Wikimedia Commons has media related to:

White frost

• Air frost
• Ground frost
• Frostbite
• Frost flowers
• Frost heaving
• Frost line
• Ice-minus bacteria
• Icing (nautical)
• Rime: soft/hard
• White frost

Notes and references

1. ^ Lindow, Stephen E.; Deane C. Arny, Christen D. Upper (October 1982). "Bacterial Ice Nucleation: A Factor in Frost Injury to Plants". Plant Physiology 70 (4): 1084-1089. PMID: 16662618. Retrieved on 2006-08-08. 
2. ^ Selective Inverted Sink Rolex Awards site (won award in Technology and Innovation category) 1998.

External links

• Clouds R Us - Frost
• Guide to Frost
• BBC Understanding Weather - Frost
• American Meteorological Society, Glossary of Meteorology - Hoarfrost
• The Weather Doctor - Weather Whys - Frost

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - frost, kulde, fiasko
v. tr. - glasere med sukker, dække med rimfrost, frostskade, mattere
v. intr. - fryse til

idioms:

• degrees of frost    frostgrader

Nederlands (Dutch)
vorst, vriespunt, koud gedrag/karakter, flop, rijp, met rijp/ suikerglazuur bedekken, mat maken (van glas/ metaal etc.), (beschadigen door) bevriezen, boos maken/ worden, grijs maken (haar), met spijkers beslaan tegen glijden

Français (French)
n. - gel, givre, gelée
v. tr. - givrer, glacer, geler (un arbre fruitier), dépolir (le verre), (Culin) glacer
v. intr. - se givrer, se couvrir de givre

idioms:

• degrees of frost    température au-dessous de zéro

Deutsch (German)
n. - Reif, Frost, Frostigkeit, (Slang) Mißerfolg
v. - mit Reif überziehen, mattieren, glasieren

idioms:

• degrees of frost    Grad minus

Ελληνική (Greek)
n. - παγετός, παγωνιά, πάχνη
v. - καλύπτω/-ομαι με πάχνη ή παγοκρυστάλλους, (για τζάμια κ.λπ.) θολώνω, θαμπώνω, καίω (φυτά), πασπαλίζω με ζάχαρη

idioms:

• degrees of frost    (Βρετ.) βαθμοί θερμοκρασίας κάτω του μηδενός

Italiano (Italian)
brina, gelo, congelare

idioms:

• degrees of frost    gradi sotto zero

Português (Portuguese)
n. - geada (f)
v. - gear, cobrir (bolo)

idioms:

• degrees of frost    temperatura (f) abaixo de zero

Русский (Russian)
мороз, иней, суровость, холод, покрываться инеем, посыпать сахаром

idioms:

• degrees of frost    градусов мороза

Español (Spanish)
n. - escarcha, helada
v. tr. - helar, congelar, cubrir de escarcha
v. intr. - helarse, cubrirse de escarcha

idioms:

• degrees of frost    grados bajo cero

Svenska (Swedish)
n. - frost, bakslag
v. - frostskada, bekläda med frost, brodda (hästar), glasera (med socker), mattslipa, göra hår vitt (poet.)

中文（简体） (Chinese (Simplified))
霜, 冷漠, 冰冻, 覆着霜, 结霜, 冻结, 受冻, 起霜

idioms:

• degrees of frost    冰点以下之度数

中文（繁體） (Chinese (Traditional))
n. - 霜, 冷漠, 冰凍
v. tr. - 覆著霜, 結霜, 凍結
v. intr. - 受凍, 起霜

idioms:

• degrees of frost    冰點以下之度數

한국어 (Korean)
n. - 한기, 서리, 결빙, 냉담함
v. tr. - 서리로 덮다
v. intr. - 얼다, 서리가 내리다

日本語 (Japanese)
n. - 霜, 霜が降りること, 寒さ, 氷結, 失敗, 不評, 凍結, 冷たさ
v. - 霜で覆う, 凍らせる, 霜枯れにさせる, つや消しにする, 糖衣で覆う

idioms:

• degrees of frost    華氏氷点下

العربيه (Arabic)
‏(الاسم) صقيع , تجمد (فعل) يتجمد‏

עברית (Hebrew)
n. - ‮קור, כפור, כישלון, אירוע משעמם‬
v. tr. - ‮השמיד בכפור, עימם זכוכית, איבק (בסוכר), זיגג‬
v. intr. - ‮כוסה כפור‬

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