[frawst, frost]
Frost, Arthur Burdett, 1851-1928, American illustrator and cartoonist, b. Philadelphia; pupil of Thomas Eakins at the Pennsylvania Academy of the Fine Arts. He worked chiefly in New York City and became one of the most popular illustrators of his time. His most characteristic drawings portrayed various aspects of American rural life, but he is best known for his illustrations of Joel Chandler Harris's "Uncle Remus" stories.
Frost, Robert, 1874-1963, American poet, b. San Francisco. Perhaps the most popular and beloved of 20th-century American poets, Frost wrote of the character, people, and landscape of New England. He was taken to Lawrence, Mass., his family's home for generations, at the age of 10. After studying briefly at Dartmouth, he worked as a bobbin boy in a cotton mill, as a cobbler, a schoolteacher, and a journalist; he later entered Harvard but left after two years to try farming. In 1912 he went to England, where he received his first acclaim as a poet. After the publication of A Boy's Will (1913) and North of Boston (1914), he returned to the United States, settling on a farm near Franconia, N.H. Frost taught and lectured at several universities, including Amherst, Harvard, and the Univ. of Michigan. In later life he was accorded many honors; he made several goodwill trips for the U.S. State Dept., and in 1961 he recited his poem "The Gift Outright" at the inauguration of President John F. Kennedy.

Among Frost's volumes of poetry are New Hampshire (1923), West-running Brook (1928), Collected Poems (1930), A Further Range (1936), A Witness Tree (1942), Steeple Bush (1947), and In the Clearing (1962). A Masque of Reason (1945) and A Masque of Mercy (1947) were blank verse plays. Although his work is rooted in the New England landscape, Frost was no mere regional poet. The careful local observations and homely details of his poems often have deep symbolic, even metaphysical, significance. His poems are concerned with human tragedies and fears, his reaction to the complexities of life, and his ultimate acceptance of his burdens. Frost was awarded the Pulitzer Prize for poetry in 1924, 1931, 1937, and 1943. Frost's critical reputation has recently rebounded after a period when his poetry was often criticized for being old-fashioned.

See his complete poems (1967); his Collected Poems, Prose and Plays (1995), ed. by R. Poirier and M. Richardson; his letters (1972), ed. by A. Grade; biographies by M. L. Mertens (1965), L. R. Thompson (2 vol., 1966-70, vol. III, with R. H. Winnick, 1976), W. H. Pritchard (1985), S. Burnshaw (1986), J. Meyers (1996), and J. Parini (1999); studies by R. A. Brower (1963), F. Lentricchia (1975), and R. Poirier (1977).

frost or hoarfrost, ice formed by the condensation of atmospheric water vapor on a surface when the temperature of the surface is below 32°F; (0°C;). In the formation of frost, a gas (water vapor) is changed directly to a solid (see dew). Frost often appears as a light feathery deposit of ice, often of a curious and delicate pattern. The dates on which killing frosts (frost destructive to vegetation and staple agricultural products) occur vary considerably. Maps showing the growing season and the probable date of occurrence of frost may be obtained from the U.S. National Weather Service. The Weather Service stations issue warnings when frost is likely to occur; such warnings are broadcast by radio and are telegraphed or telephoned to farmers and fruitgrowers, who may protect their crops accordingly. Methods of protection vary: small flower beds and vegetable gardens are commonly protected by a screen or cloth that prevents excessive radiation from the earth and from the plants; in orchards, especially in California and Florida, simple oil-burning stoves or smudge pots placed at intervals throughout an orchard are used to heat and circulate the air sufficiently to prevent frost. Valleys are more subject to frosts than slopes, since cold air "slides" downhill and settles in depressions; orchards and citrus fruit groves are usually planted on slopes. Other factors in the occurrence of frost are altitude, latitude, proximity to large bodies of water, and other determinants of temperature. Frost, an element of climate, is an important agent of erosion. Frost heaving, an upthrust of ground caused by freezing, is a factor of consideration in engineering construction, especially in highway foundations. Frost is also a factor in the layer by layer mechanical weathering (exfoliation) of many types of rock masses. In England the word frost denotes freezing weather and degrees of frost means the number of degrees that the temperature falls below the freezing point.

See R. L. Berg and E. Wright Frost Action and Its Control (1984).

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. 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. Road surfaces can also be damaged through a process known as frost heaving.


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.

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.


Hoar frost

Radiation frost

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 radiation 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.

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 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.

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. 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.

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.


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


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

Protection methods

The Selective Inverted Sink 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.

See also


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