Frost is a solid deposition of water vapor from saturated air. Deposition is a process in which gas transforms into solid (also known as desublimation General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated In Chemistry, saturation has five different meanings In Physical chemistry, saturation is the point at which a Solution of a substance It is formed when solid surfaces are cooled to below the dew point of the adjacent air. The dew point (sometimes spelled dewpoint) is the Temperature to which a given parcel of Air must be cooled at constant Barometric pressure, ^[1] Frost crystals' size differ depending on time and water vapor available. Frost is also usually translucent in appearance. In Optics, transparency (also called pellucidity) is the Material property of allowing There are many types of frost, such as radiation and window frost. Frost causes economic damage when it destroys plants or hanging fruits. It can also damage road surfaces through a process known as frost heaving. Frost heaving (or frost heave) occurs when Soil expands and contracts due to freezing and thawing

Contents 1 Formation 2 Types of Frost 2.1 Hoar frost 2.1.1 Radiation frost 2.1.2 Advection frost 2.1.3 Window frost 2.1.4 Frost flowers 2.2 Rime 3 Effect on plants 4 See also 5 Notes and references 6 External links

Formation

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. The dew point (sometimes spelled dewpoint) is the Temperature to which a given parcel of Air must be cooled at constant Barometric pressure, Frost consists of spicules of ice which grow out from the solid surface. This article is about the skeletal structure See also Spicule (solar physics and Spicule (glass manufacture. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia The size of the crystals depends on time, temperature, and the amount of water vapor available. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated

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. Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantity The emissivity of a material (usually written \epsilon is the ratio of energy radiated by a particular material to energy radiated by a Black body at 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. In

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".

The formation of frost is an example of meteorological deposition. Deposition is a process in which gas transforms into solid (also known as desublimation

Types of Frost

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. Ice crystals - small crystalline form of Ice including hexagonal columns hexagonal plates dendritic crystals and Diamond dust.

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. This article refers to the natural event For other uses see Avalanche (disambiguation An avalanche is an abrupt and rapid flow of snow often 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. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. For freezing as a method of food preservation see Frozen food. A refrigerator (often called a " fridge " for short is a cooling appliance comprising a thermally insulated compartment and a Heat pump - Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater 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. Relative humidity is a measurement of the amount of Water vapor that exists in a gaseous mixture of air and water Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase Clear ice refers to a solid precipitation which forms when Air temperature is between 0  °C (32  °F) and -3 °C (27 °F

Frost flowers

Frost flowers occur when there is a freezing weather condition but the ground is not already frozen. Frost flowers is the name commonly given to a condition in which thin layers of Ice are extruded from long-stemmed plants in Autumn or early winter Frost flowers is the name commonly given to a condition in which thin layers of Ice are extruded from long-stemmed plants in Autumn or early winter The water contained in the plant stem expands and causes long cracks along. A stem is one of two main structural axes of a Vascular plant. Water, via capillary action, goes out from the cracks and freezes on contact with the air. Capillary action, capillarity, capillary motion, or wicking is the ability of a substance to draw another substance into it

Rime

Rime is a type of frost that occurs quickly, often under conditions of heavily saturated air and windy conditions. Hard rime is a white Ice that forms when the Water droplets in Fog freeze to the outer surfaces of objects 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. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Certain bacteria, notably Pseudomonas syringae, are particularly effective at triggering frost formation, raising the nucleation temperature to about −2°C^[2]. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Pseudomonas syringae is a rod shaped Gram-negative Bacterium with polar Flagella. Bacteria lacking ice nucleation-active proteins (ice-minus bacteria) result in greatly reduced frost damage^[3]. Nucleation is the onset of a Phase transition in a small region Ice-minus bacteria is a nickname given to a variant of the common Bacterium Pseudomonas syringae ( P

The Selective Inverted Sink ^[4] prevents frost by drawing cold air from the ground and blowing it up through a chimney. The selective inverted sink or SIS is a device used by Farmers to protect plants from Frost, developed by Uruguayan Rafael Guarga in the late 1990s It was originally developed to prevent frost damage to citrus fruits in Uruguay. Citrus is a common term and Genus of Flowering plants in the family Rutaceae, originating in tropical and subtropical southeast regions of Uruguay.(official full name in República Oriental del Uruguay;, Oriental Republic of Uruguay) is a country located in the southeastern part of South America

See also

• The Wikimedia Commons has media related to Hoar frost.

• Media related to White frost from the Wikimedia Commons.

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

Notes and references

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

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