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From Wikipedia, the free encyclopedia

Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water.[1] Frost crystals' size differ depending on time and water vapor available. Frost is also usually translucent in appearance. There are many types of frost, such as radiation and window frost. Frost causes economic damage when it destroys plants or hanging fruits.

Contents

Formation

Frost on black pipes.

If a solid surface is chilled below the dew point of the surrounding air and the surface itself is colder than freezing, frost will form on the surface. Frost consists of spicules of ice which grow out from the solid surface. The size of the crystals depends on time, temperature, and the amount of water vapor available. Based on wind direction, "Frost arrows" might form.

In general, for frost to form the deposition surface must be colder than the surrounding air. For instance frost may be observed around cracks in cold wooden sidewalks when moist air escapes from the ground below. Other objects on which frost tends to form are those with low specific heat or 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 denser 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".

The formation of frost is an example of meteorological deposition.

Types

Radiation frost

A thin layer of frost will melt quickly, when exposure to sunlight raises an underlying object's temperature above the melting-point of water.
Hoar frost or soft rime on a cold winter day in Lower Saxony
Hoar frost visible on a blade of grass in England
Interior Alaska Ice Iris
Window frost on a skylight (contrast enhanced)
Rime frost
Frost on a grave, Netherlands
Large feathery crystals
Frost on a car window.

Radiation frost (also called hoar frost or hoarfrost) refers to the white ice crystals, loosely deposited on the ground or exposed objects, that form on cold clear nights when heat losses into the open skies cause objects to become colder than the surrounding air. A related effect is flood frost which occurs when air cooled by ground-level radiation losses travels downhill to form pockets of very cold air in depressions, valleys, and hollows. Hoar frost can form in these areas even when the air temperature a few feet above ground is well above freezing. Nonetheless the frost itself will be at or below the freezing temperature of water.

Hoar frost may have different names 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.

Surface hoar is a cause of avalanches when it forms on top of snow. Conditions that are ideal are cold clear nights, with a very light wind that is able to circulate more humidified air around the snow surface. Wind that is too abrupt will destroy the crystals. When buried by subsequent snows they may remain standing for easy identification, or become laid down, but still dangerous because of the weakness of the crystals

Hoar frost also occurs around man-made environments such as freezers or industrial cold storage facilities. It occurs in adjacent rooms that are not well insulated against the cold or around entry locations where humidity and moisture will enter and freeze instantly depending on the freezer temperature.

Advection frost

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.

Frost flowers

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 the stem. Water, via capillary action, goes out from the cracks and freezes on contact with the air. Also the frost can literally look like a flower, even a dead flower from the previous summer. These are rare and wonderful to see as they are very delicate and last usually less than a day. Due to their fleeting nature, they are difficult to find to photograph and the locations of these Frost Flowers are elusive as terrain plays a big part in their formation as well.

Window frost

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. With very low temperatures outside frost can appear on the bottom of the window even with double pane energy efficient windows, due to air convection between two panes of glass. The bottom part of the glazing unit is always colder than the top part. The glass surface influences the shape of crystals, so imperfections, scratches or dust can modify the way ice nucleates. If the indoor air is very humid, rather than moderately so, water would first condense in small droplets and then freeze into clear ice.

Rime

Rime is a type of frost that occurs quickly, often under conditions of heavily saturated air and windy conditions. Ships traveling through Arctic seas may accumulate rime on the rigging. Unlike hoar frost, which has a feathery appearance, rime generally has an icy solid appearance. In contrast to the formation of hoar frost, in which the water vapor condenses slowly and directly into icy feathers, Rime typically goes through a liquid phase where the surface is wet by condensation before freezing.

Effect on plants

Overview

Frost on a nettle.
Frost on lingonberry leaves.

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, become dormant after first frosts and regrow when spring arrives. The entire visible plant may turn completely 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. Frost crack is a bark defect caused by a combination of low temperatures and heat from the winter sun.

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. Hardening is the process by which a plant becomes tolerant to low temperatures. See also cryobiology.

Certain bacteria, notably Pseudomonas syringae, are particularly effective at triggering frost formation, raising the nucleation temperature to about −2°C[2]. Bacteria lacking ice nucleation-active proteins (ice-minus bacteria) result in greatly reduced frost damage[3].

Protection methods

The Selective Inverted Sink [4] 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.

In New Zealand, helicopters are used in a similar function, especially in the vineyard regions like Marlborough. By dragging down warmer air from the inversion layers, and preventing the ponding of colder air on the ground, the low-flying helicopters prevent damage to the fruit buds. As the operations are conducted at night, and have in the past involved up to 130 aircraft per night in one region, safety rules are strict.[5]

Personifications

Frost is personified in Russian culture as Ded Moroz. Indigenous peoples of Russia such as the Mordvins have their own traditions of frost deities.

English folklore tradition holds that Jack Frost, an elfish creature, is responsible for feathery patterns of frost found on windows on cold mornings.

See also

References

  1. ^ "What causes frost?". http://www.weatherquestions.com/What_causes_frost.htm. Retrieved 2007-12-05. 
  2. ^ Maki LR, Galyan EL, Chang-Chien MM, Caldwell DR (1974). "Ice nucleation induced by pseudomonas syringae". Applied Microbiology 28 (3): 456–459. PMID 4371331. 
  3. ^ 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. doi:10.1104/pp.70.4.1084. PMID 16662618. http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=16662618. Retrieved 2006-08-08. 
  4. ^ Selective Inverted Sink Rolex Awards site (won award in Technology and Innovation category) 1998.
  5. ^ Helicopters Fight Frost - Vector, Civil Aviation Authority of New Zealand, September / October 2008, Page 8-9

External links


Travel guide

Up to date as of January 14, 2010

From Wikitravel

Frost is a city in Faribault County, Southern Minnesota.

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Source material

Up to date as of January 22, 2010
(Redirected to The Frost article)

From Wikisource

The Frost
by Hannah Flagg Gould
"Jack Frost," by Hannah Flagg Gould (1789-1865), is perhaps a hundred years old, but he is the same rollicking fellow to-day as of yore. The poem puts his merry pranks to the front and prepares the way for science to give him a true analysis.

    The Frost looked forth, one still, clear night,
    And whispered, "Now I shall be out of sight;
    So through the valley and over the height,
      In silence I'll take my way:
    I will not go on with that blustering train,
    The wind and the snow, the hail and the rain,
    Who make so much bustle and noise in vain,
      But I'll be as busy as they."

    Then he flew to the mountain and powdered its crest;
    He lit on the trees, and their boughs he dressed
    In diamond beads--and over the breast
      Of the quivering lake he spread
    A coat of mail, that it need not fear
    The downward point of many a spear
    That hung on its margin far and near,
      Where a rock could rear its head.

    He went to the windows of those who slept,
    And over each pane, like a fairy, crept;
    Wherever he breathed, wherever he slept,
      By the light of the moon were seen
    Most beautiful things--there were flowers and trees;
    There were bevies of birds and swarms of bees;
    There were cities with temples and towers, and these
      All pictured in silver sheen!

    But he did one thing that was hardly fair;
    He peeped in the cupboard, and finding there
    That all had forgotten for him to prepare--
     "Now just to set them a-thinking,
    I'll bite this basket of fruit," said he,
   "This costly pitcher I'll burst in three,
    And the glass of water they've left for me
      Shall '_tchich!_' to tell them I'm drinking."


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

FROST (a common Teutonic word, cf. Dutch, vorst, Ger. Frost, from the common Teutonic verb meaning "to freeze," Dutch, vriezen, Ger. frieren; the Indo-European root is seen in Lat. pruina, hoar-frost, cf. prurire, to itch, burn, pruna, burning coal, Sansk. plush, to burn), in meteorology, the act, or agent of the process, of freezing; hence the terms "hoar-frost" and "whitefrost" applied to visible frozen vapour formed on exposed surfaces. A frost can only occur when the surface temperature falls below 32° F., the freezing-point of water; if the temperature be between 28° and 32° it is a "light frost," if below 28° it is a "heavy," "killing" or "black frost"; the term "black frost" is also used when no hoar-frost is present. The number of degrees below freezing-point is termed "degrees of frost." As soon as a mass of air is cooled to its dew-point, water begins to be precipitated in the form of rain, dew, snow or hail. Hoarfrost is only formed at the immediate surface of the land if the latter be at a temperature below 32°, and this may occur even when the temperature of the air a few feet above the ground is 12°-16° above the freezing-point. The heaviest hoar-frosts are formed under weather conditions similar to those under which the heaviest summer dews occur, namely, clear and calm nights, when there is no cloud to impede the radiation of heat from the surface of the land, which thereby becomes rapidly and completely cooled. The danger of frost is minimized when the soil is very moist, as for example after 10-12 mm. of rain; and it is a practice in America to flood fields on the receipt of a frost warning, radiation being checked by the light fog sheets which develop over moist soils, just as a cloud-layer in the upper atmosphere impedes radiation on a grand scale. A layer of smoke will also impede radiation locally, and to this end smoky fires are sometimes lit in such positions that the smoke may drift over planted ground which it is desirable to preserve from frost. Similarly, frost may occur in open country when a town, protected by its smoke-cloud above, is free of it. In a valley with fairly high and steep flanks frost sometimes occurs locally at the bottom, because the layer of air cooled by contact with the cold surface of the higher ground is heavier than that not so cooled, and therefore tends to flow or settle downwards along the slope of the land. When meteorological considerations point to a frost, an estimate of the night temperature may be obtained by multiplying the difference between the readings of the wet and dry bulb thermometer by 2.5 and subtracting the result from the dry bulb temperature. This rule applies when the evening air is at about 50° and 30 i-in. pressure, the sky being clear. An instrument has been devised in France for the prediction of frost. It consists of a wet bulb and a dry bulb thermometer, mounted on a board on which is also a scale of lines corresponding to degrees of the dry bulb, and a pointer traversing a scale graduated according to degrees of the wet bulb. Observations for the night are taken about half an hour before sunset. By means of the pointer and scale, the point may be found at which the line of the dry-bulb reading meets the pointer set to the reading of the wet bulb. The scale is further divided by colours so that the observed point may fall within one of three zones, indicating certain frost, probable frost or no probability of frost.


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Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also frost

German

Etymology

Old High German frost

Noun

Frost m.

  1. frost

Wikispecies

Up to date as of January 23, 2010
(Redirected to Darrel Frost article)

From Wikispecies

Darrel Frost, Curator of Herpetology American Museum of Natural History

External links


Bible wiki

Up to date as of January 23, 2010

From BibleWiki

(Heb. kerah, from its smoothness) Job 37:10 (R.V., "ice"); Gen 31:40; Jer 36:30; rendered "ice" in Job 6:16, Job 38:29; and "crystal" in Ezek 1:22. "At the present day frost is entirely unknown in the lower portions of the valley of the Jordan, but slight frosts are sometimes felt on the sea-coast and near Lebanon." Throughout Western Asia cold frosty nights are frequently succeeded by warm days.

"Hoar frost" (Heb. kephor, so called from its covering the ground) is mentioned in Ex 16:14; Job 38:29; Ps 14716.

In Ps 7847 the word rendered "frost" (R.V. marg., "great hail-stones"), hanamal, occurs only there. It is rendered by Gesenius, the Hebrew lexicographer, "ant," and so also by others, but the usual interpretation derived from the ancient versions may be maintained.

This entry includes text from Easton's Bible Dictionary, 1897.

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Simple English

Frost is ice that is formed when water vapor freezes onto a surface. It has a white, powdery appearance. It forms on outside surfaces when the temperature of air is very low. It can destroy crops. Greenhouses help to protect crops from frost.









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