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73-498: 'Old Blush' has light silvery pink semi-double flowers of medium size that darken as they age. They bloom in fives and have a light to strong tea fragrance, a cupped to flat bloom form, and an average diameter of 7 centimetres (2.8 in). The red buds appear in clusters almost continuously from early June to the first frost - in warmer regions even throughout the year, and can develop to small, red rose hips . The shrub has an arching form, few prickles and mid-green leaves that have

146-445: A {\displaystyle Ra} is a dimensional unit that can be micrometer or microinch . Since these parameters reduce all of the information in a profile to a single number, great care must be taken in applying and interpreting them. Small changes in how the raw profile data is filtered, how the mean line is calculated, and the physics of the measurement can greatly affect the calculated parameter. With modern digital equipment,

219-443: A {\displaystyle Ra} is the arithmetic average value of filtered roughness profile determined from deviations about the center line within the evaluation length and R t {\displaystyle Rt} is the range of the collected roughness data points. The arithmetic average roughness, R a {\displaystyle Ra} , is the most widely used one-dimensional roughness parameter. Here

292-484: A {\displaystyle Ra} value, or a positive R s k {\displaystyle Rsk} , will usually have somewhat higher friction and wear quickly. The peaks in the roughness profile are not always the points of contact. The form and waviness (i.e. both amplitude and frequency) must also be considered. In Earth Sciences (e.g., Shepard et al., 2001; Smith, 2014 ) and Ecology (e.g., Riley et al., 1999; Sappington et al., 2007 ) surface roughness has

365-537: A and λ {\displaystyle \lambda } q . S m is the mean spacing between peaks. Just as with real mountains it is important to define a "peak". For S m the surface must have dipped below the mean surface before rising again to a new peak. The average wavelength λ {\displaystyle \lambda } a and the root mean square wavelength λ {\displaystyle \lambda } q are derived from Δ {\displaystyle \Delta }

438-408: A freezing surface. Frost forms when the air contains more water vapor than it can normally hold at a specific temperature. The process is similar to the formation of dew , except it occurs below the freezing point of water typically without crossing through a liquid state. Air always contains a certain amount of water vapor, depending on temperature. Warmer air can hold more than colder air. When

511-419: A surface profile measurement is made with a profilometer . These can be of the contact variety (typically a diamond stylus) or optical (e.g.: a white light interferometer or laser scanning confocal microscope ). However, controlled roughness can often be desirable. For example, a gloss surface can be too shiny to the eye and too slippery to the finger (a touchpad is a good example) so a controlled roughness

584-467: A "hard frost" below −2 °C (28 °F). Plants likely to be damaged even by a light frost include vines—such as beans, grapes, squashes, melons—along with nightshades such as tomatoes, eggplants, and peppers. Plants that may tolerate (or even benefit from) frosts include: Even those plants that tolerate frost may be damaged once temperatures drop even lower (below −4 °C or 25 °F). Hardy perennials, such as Hosta , become dormant after

657-416: A . When trying to understand a surface that depends on both amplitude and frequency it is not obvious which pair of metrics optimally describes the balance, so a statistical analysis of pairs of measurements can be performed (e.g.: R z and λ {\displaystyle \lambda } a or R a and Sm) to find the strongest correlation. Common conversions: These parameters are based on

730-421: A crimson colour when young. It grows 100 to 150 centimetres (3.3 to 4.9 ft) tall and about 90 to 120 centimetres (3.0 to 3.9 ft) wide, tolerates half shade, poor soils, and is winter hardy down to -18 °C ( USDA zone 6 to 7). The cultivar can be trained as a small climber, reaching up to 2.5 metres (8.2 ft) height which has larger flowers. The cultivar was one of the four cultivars inducted into

803-765: A full-scale representation of a typical machined surface affected by tool feed marks; it ignores the geometry of the cutting edge. (J. Paulo Davim, 2010, op.cit .). Fractal descriptors of surfaces have an important role to play in correlating physical surface properties with surface structure. Across multiple fields, connecting physical, electrical and mechanical behavior with conventional surface descriptors of roughness or slope has been challenging. By employing measures of surface fractality together with measures of roughness or surface shape, certain interfacial phenomena including contact mechanics, friction and electrical contact resistance, can be better interpreted with respect to surface structure. Areal roughness parameters are defined in

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876-438: A glass pane is exposed to very cold air on the outside and warmer, moderately moist air on the inside. If the pane is a bad insulator (for example, if it is a single-pane window), water vapour condenses on the glass, forming frost patterns. With very low temperatures outside, frost can appear on the bottom of the window even with double-pane energy-efficient windows because the air convection between two panes of glass ensures that

949-475: A heavy coating of hoar frost with big, interlocking crystals, usually needle-shaped. Rime is a type of ice deposition that occurs quickly, often under heavily humid and windy conditions. Technically speaking, it is not a type of frost, since usually supercooled water drops are involved, in contrast to the formation of hoar frost, in which water vapour desublimates slowly and directly. Ships travelling through Arctic seas may accumulate large quantities of rime on

1022-431: A key role in governing contact mechanics , that is to say the mechanical behavior exhibited at an interface between two solid objects as they approach each other and transition from conditions of non-contact to full contact. In particular, normal contact stiffness is governed predominantly by asperity structures (roughness, surface slope and fractality) and material properties. In terms of engineering surfaces, roughness

1095-600: 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 (28 °F). Bacteria lacking ice nucleation-active proteins ( ice-minus bacteria ) result in greatly reduced frost damage. Typical measures to prevent frost or reduce its severity include one or more of: Such measures need to be applied with discretion, because they may do more harm than good; for example, spraying crops with water can cause damage if

1168-479: A process similar to the formation of dust bunnies and similar structures. Hoar frost and white frost also occur in man-made environments such as in freezers or industrial cold-storage facilities. If such cold spaces or the pipes serving them are not well insulated and are exposed to ambient humidity, the moisture will freeze instantly depending on the freezer temperature. The frost may coat pipes thickly, partly insulating them, but such inefficient insulation still

1241-408: A purpose. Roughness plays an important role in determining how a real object will interact with its environment. In tribology , rough surfaces usually wear more quickly and have higher friction coefficients than smooth surfaces. Roughness is often a good predictor of the performance of a mechanical component, since irregularities on the surface may form nucleation sites for cracks or corrosion. On

1314-696: A quite broad meaning (e.g. Smith, 2014), with multiple definitions, and generally it is considered a multi-scale property related to surface spatial variability; it is often referred as surface texture (e.g., Trevisani et al., 2012 ), given the evident analogies to image texture (e.g., Haralick et al. 1973; Lucieer and Stein, 2005 ) when the analysis is performed on digital elevation models. From this perspective there are various interlinks with methodologies related to geostatistics (e.g., Herzfeld and Higginson, 1996 ), fractal analysis (e.g. Bez and Bertrand, 2011 ) and pattern recognition (e.g., Ojala et al. 2002 ), including many interrelations with remote sensing approaches. In

1387-428: A soil surface, as well as their stochastic distribution. There are four distinct classes of SSR, each one of them representing a characteristic vertical length scale; the first class includes microrelief variations from individual soil grains to aggregates on the order of 0.053–2.0 mm; the second class consists of variations due to soil clods ranging between 2 and 100 mm; the third class of soil surface roughness

1460-453: Is a common conversion table with roughness grade numbers: Slope parameters describe characteristics of the slope of the roughness profile. Spacing and counting parameters describe how often the profile crosses certain thresholds. These parameters are often used to describe repetitive roughness profiles, such as those produced by turning on a lathe . Other "frequency" parameters are S m , λ {\displaystyle \lambda }

1533-520: Is a consequence of the nucleation process being constrained to unfold in two dimensions, unlike a snowflake, which is shaped by a similar process, but forms in three dimensions and has a fractal dimension greater than two. If the indoor air is very humid, rather than moderately so, water first condenses in small droplets, and then freezes into clear ice . Similar patterns of freezing may occur on other smooth vertical surfaces, but they seldom are as obvious or spectacular as on clear glass. White frost

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1606-431: Is a solid deposition of ice that forms directly from water vapour contained in air. White frost forms when relative humidity is above 90% and the temperature below −8 °C (18 °F), and it grows against the wind direction, since air arriving from windward has a higher humidity than leeward air, but the wind must not be strong, else it damages the delicate icy structures as they begin to form. White frost resembles

1679-413: Is a source of heat loss. Advection frost (also called wind frost ) refers to tiny ice spikes that form when very cold wind is blowing over tree branches, poles, and other surfaces. It looks like rimming on the edges of flowers and leaves, and usually forms against the direction of the wind . It can occur at any hour, day or night. Window frost (also called fern frost or ice flowers ) forms when

1752-406: Is called "killing frost" because white frost tends to be less cold, partly because the latent heat of freezing of the water reduces the temperature drop. Many plants can be damaged or killed by freezing temperatures or frost. This varies with the type of plant, the tissue exposed, and how low temperatures get; a "light frost" of −2 to 0 °C (28 to 32 °F) damages fewer types of plants than

1825-424: Is composed of peaks on an otherwise smooth surface and the other is composed of troughs of the same amplitude. Such tools can be found in app format. By convention every 2D roughness parameter is a capital R {\displaystyle R} followed by additional characters in the subscript. The subscript identifies the formula that was used, and the R {\displaystyle R} means that

1898-435: Is considered to be detrimental to part performance. As a consequence, most manufacturing prints establish an upper limit on roughness, but not a lower limit. An exception is in cylinder bores where oil is retained in the surface profile and a minimum roughness is required. Surface structure is often closely related to the friction and wear properties of a surface. A surface with a higher fractal dimension , large R

1971-458: Is difficult and expensive to control surface roughness of fused deposition modelling (FDM) manufactured parts. Decreasing the roughness of a surface usually increases its manufacturing cost. This often results in a trade-off between the manufacturing cost of a component and its performance in application. Roughness can be measured by manual comparison against a "surface roughness comparator" (a sample of known surface roughness), but more generally

2044-633: Is due partly to differences of elevation, the lower areas becoming colder on calm nights. Where static air settles above an area of ground in the absence of wind, the absorptivity and specific heat of the ground strongly influence the temperature that the trapped air attains. 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

2117-460: Is forced out of solution, resulting in a phase change directly from water vapor (a gas ) to ice (a solid). As more water molecules are added to the seeds, crystal growth occurs, forming ice crystals . Crystals may vary in size and shape, from an even layer of numerous microscopic-seeds to fewer but much larger crystals, ranging from long dendritic crystals (tree-like) growing across a surface, acicular crystals (needle-like) growing outward from

2190-520: Is most commonly quantified by means of the Random Roughness, which is essentially the standard deviation of bed surface elevation data around the mean elevation, after correction for slope using the best-fit plane and removal of tillage effects in the individual height readings. Rainfall impact can lead to either a decay or increase in microroughnesss, depending upon initial microroughness conditions and soil properties. On rough soil surfaces,

2263-411: Is not necessarily 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 to −12 °C (25 to 10 °F). However, once frost forms, the leaf cells may be damaged by sharp ice crystals. Hardening is the process by which

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2336-553: 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. In 2024, two European Space Agency spacecraft, Exomars TGO and Mars Express , discovered a thin but very wide layer of water frost on

2409-665: Is required. This is a case where both amplitude and frequency are very important. A roughness value can either be calculated on a profile (line) or on a surface (area). The profile roughness parameter ( R a {\displaystyle Ra} , R q {\displaystyle Rq} , ...) are more common. The area roughness parameters ( S a {\displaystyle Sa} , S q {\displaystyle Sq} , ...) give more significant values. The profile roughness parameters are included in BS EN ISO 4287:2000 British standard, identical with

2482-413: Is systematic elevation differences due to tillage, referred to as oriented roughness (OR), ranging between 100 and 300 mm; the fourth class includes planar curvature, or macro-scale topographic features. The two first classes account for the so-called microroughness, which has been shown to be largely influenced on an event and seasonal timescale by rainfall and tillage, respectively. Microroughness

2555-392: Is the arithmetic average of the 3D roughness. Each of the formulas listed in the tables assumes that the roughness profile has been filtered from the raw profile data and the mean line has been calculated. The roughness profile contains n {\displaystyle n} ordered, equally spaced points along the trace, and y i {\displaystyle y_{i}}

2628-479: Is the vertical distance from the mean line to the i th {\displaystyle i^{\text{th}}} data point. Height is assumed to be positive in the up direction, away from the bulk material. Amplitude parameters characterize the surface based on the vertical deviations of the roughness profile from the mean line. Many of them are closely related to the parameters found in statistics for characterizing population samples. For example, R

2701-620: The R k {\displaystyle Rk} family of parameters is used mainly for cylinder bore linings, and the Motif parameters are used primarily in the French automotive industry. The MOTIF method provides a graphical evaluation of a surface profile without filtering waviness from roughness. A motif consists of the portion of a profile between two peaks and the final combinations of these motifs eliminate ″insignificant″ peaks and retains ″significant″ ones. Please note that R

2774-631: The Old Rose Hall of Fame by the World Federation of Rose Societies at its creation in 1988. 'Old Blush', together with 'Slater's Crimson China' and the tea roses 'Hume's Blush Tea-scented China' and 'Parks' Yellow Tea-scented China', introduced to European gardens roses which would bloom repeatedly from spring to fall, whereas the Old European roses tend to bloom only once, on the previous year's wood. The chinas and teas became

2847-433: The atmosphere contains more water than it can hold at a specific temperature, its relative humidity rises above 100% becoming supersaturated , and the excess water vapor is forced to deposit onto any nearby surface, forming seed crystals . The temperature at which frost will form is called the dew point , and depends on the humidity of the air. When the temperature of the air drops below its dew point, excess water vapor

2920-541: The bearing ratio curve (also known as the Abbott-Firestone curve.) This includes the Rk family of parameters. The mathematician Benoît Mandelbrot has pointed out the connection between surface roughness and fractal dimension . The description provided by a fractal at the microroughness level may allow the control of the material properties and the type of the occurring chip formation. But fractals cannot provide

2993-540: The contiguous United States , southern Florida around Miami Beach and the Florida Keys are the only reliably frost-free areas, as well as the Channel Islands off the coast of California . The hardiness zones in these regions are 11a and 11b. Permafrost is a layer of frozen earth underground which never heats above freezing even during summer months, remaining frozen year round. Although not frost in

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3066-418: The liquid phase . The air must be humid, but not sufficiently humid to permit the condensation of liquid water, or icing will result instead of desublimation. The size of the crystals depends largely on the temperature, the amount of water vapor available, and how long they have been growing undisturbed. As a rule, except in conditions where supercooled droplets are present in the air, frost will form only if

3139-407: The normal vector of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small, the surface is smooth. In surface metrology , roughness is typically considered to be the high-frequency, short-wavelength component of a measured surface. However, in practice it is often necessary to know both the amplitude and frequency to ensure that a surface is fit for

3212-537: The Earth to reach deep enough to thaw the permafrost layer. The permafrost may begin from the surface of the ground or many meters beneath it, and may extend from just a meter to over a thousand meters in thickness. Permafrost contains a significant portion of the Earth's water and carbon, and prevents surface water from penetrating very deep into the ground, making it responsible in part for the typical taiga and spruce bog environments common in northern latitudes. Frost

3285-500: The ISO 25178 series. The resulting values are Sa, Sq, Sz,... Many optical measurement instruments are able to measure the surface roughness over an area. Area measurements are also possible with contact measurement systems. Multiple, closely spaced 2D scans are taken of the target area. These are then digitally stitched together using relevant software, resulting in a 3D image and accompanying areal roughness parameters. Surface structure plays

3358-690: The ISO 4287:1997 standard. The standard is based on the ″M″ (mean line) system. There are many different roughness parameters in use, but R a {\displaystyle Ra} is by far the most common, though this is often for historical reasons and not for particular merit, as the early roughness meters could only measure R a {\displaystyle Ra} . Other common parameters include R z {\displaystyle Rz} , R q {\displaystyle Rq} , and R s k {\displaystyle Rsk} . Some parameters are used only in certain industries or within certain countries. For example,

3431-424: The air is very cold, calm, and heavily saturated, such as during an ice fog . Frost may occur when warm, moist air comes into contact with a cold surface, cooling it below its dew point, such as warm breath on a freezing window. In the atmosphere, it more often occurs when both the air and the surface are below freezing, when the air experiences a drop in temperature bringing it below its dew point, for example, when

3504-462: The air temperature a few feet above ground is well above freezing. The word "hoar" comes from an Old English adjective that means "showing signs of old age". In this context, it refers to the frost that makes trees and bushes look like white hair. Hoar frost may have different names depending on where it forms: When surface hoar covers sloping snowbanks, the layer of frost crystals may create an avalanche risk; when heavy layers of new snow cover

3577-465: The atmospheric sense, it consists of dirt, soil, sand, rocks, clay, or organic matter (peat) bound firmly together by ice crystals, making the material very hard and difficult to penetrate. Permafrost exists in the colder climates of the Arctic and Antarctic, such as Russia, Canada, Alaska, Norway, Greenland, or Antarctica, where the warmer conditions of summer are insufficient to penetrate the insulation of

3650-399: The bottom part of the glazing unit is colder than the top part. On unheated motor vehicles, the frost usually forms on the outside surface of the glass first. The glass surface influences the shape of crystals, so imperfections, scratches, or dust can modify the way ice nucleates . The patterns in window frost form a fractal with a fractal dimension greater than one, but less than two. This

3723-404: The context of geomorphometry (or just morphometry, Pike, 2000 ) the applications cover many research topics in applied and environmental geology, geomorphology, geostructural studies and soil science. An example (non exhaustive) of the related literature can be found in the following articles: Soil-surface roughness (SSR) refers to the vertical variations present in the micro- and macro-relief of

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3796-452: The deposition surface is colder than the surrounding air. For instance, frost may be observed around cracks in cold wooden sidewalks when humid air escapes from the warmer ground beneath. Other objects on which frost commonly forms 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

3869-407: The first frosts and regrow when spring arrives. The entire visible plant may turn completely brown until the spring warmth, or may drop all of its leaves and flowers, leaving the stem and stalk only. Evergreen plants, such as pine trees, 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

3942-451: The first noisette and parent of the better known 'Blush Noisette' . Two well-known sports of 'Old Blush' are 'Climbing Old Blush' (known since about 1750), one of the best climbers with slightly larger flowers than its parent, and 'Viridiflora', a green cultivar, that was introduced by Bambridge & Harrison in 1845. Frost Frost is a thin layer of ice on a solid surface, which forms from water vapor that deposits onto

4015-409: The formula was applied to a 2D roughness profile. Different capital letters imply that the formula was applied to a different profile. For example, R a {\displaystyle Ra} is the arithmetic average of the roughness profile, P a {\displaystyle Pa} is the arithmetic average of the unfiltered raw profile, and S a {\displaystyle Sa}

4088-472: The foundation of numerous new classes of roses, including the bourbons , noisettes , hybrid perpetuals , and thence the modern garden roses. 'Old Blush' itself was parent to two of these classes: a natural cross of 'Old Blush' with 'Autumn Damask' on the Ile de Bourbon gave rise to 'Rose Edouard', the first bourbon rose; and John Champneys' hybrid of 'Old Blush' with the musk rose was 'Champneys' Pink Cluster',

4161-414: The frosty surface, furry crystals standing out from the old snow hold off the falling flakes, forming a layer of voids that prevents the new snow layers from bonding strongly to the old snow beneath. Ideal conditions for hoarfrost to form on snow are cold, clear nights, with very light, cold air currents conveying humidity at the right rate for growth of frost crystals. Wind that is too strong or warm destroys

4234-405: The furry crystals, and thereby may permit a stronger bond between the old and new snow layers. However, if the winds are strong enough and cold enough to lay the crystals flat and dry, carpeting the snow with cold, loose crystals without removing or destroying them or letting them warm up and become sticky, then the frost interface between the snow layers may still present an avalanche danger, because

4307-527: The lowland tropics, where they cover almost all land except at altitudes above about 3,000 metres or 9,800 feet near the equator and around 2,000 metres or 6,600 feet in the semiarid areas in tropical regions. Some areas on the oceanic margins of the subtropics are also frost-free, as are highly oceanic areas near windward coasts. The most poleward frost-free areas are the lower altitudes of the Azores , Île Amsterdam , Île Saint-Paul , and Tristan da Cunha . In

4380-429: The other hand, roughness may promote adhesion . Generally speaking, rather than scale specific descriptors, cross-scale descriptors such as surface fractality provide more meaningful predictions of mechanical interactions at surfaces including contact stiffness and static friction . Although a high roughness value is often undesirable, it can be difficult and expensive to control in manufacturing . For example, it

4453-500: The peak of Olympus Mons , the highest mountain on Mars . This layer of frost appears for a few hours around sunrise, and then evaporates into the atmosphere for the rest of the Martian day. This was the first instance of frost discovered in the equatorial region of Mars. Surface roughness Surface roughness can be regarded as the quality of a surface of not being smooth and it is hence linked to human ( haptic ) perception of

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4526-466: The plants become overburdened with ice. An effective, low cost method for small crop farms and plant nurseries, exploits the latent heat of freezing . A pulsed irrigation timer delivers water through existing overhead sprinklers at a low volumes to combat frosts down to −5 °C (23 °F). If the water freezes, it gives off its latent heat, preventing the temperature of the foliage from falling much below zero. Frost-free areas are found mainly in

4599-811: The result of fractal process development. The depth of frost crystals varies depending on the amount of time they have been accumulating, and the concentration of the water vapor ( humidity ). Frost crystals may be invisible (black), clear ( translucent ), or, if a mass of frost crystals scatters light in all directions, the coating of frost appears white. Types of frost include crystalline frost ( hoar frost or radiation frost) from deposition of water vapor from air of low humidity, white frost in humid conditions, window frost on glass surfaces, advection frost from cold wind over cold surfaces, black frost without visible ice at low temperatures and very low humidity, and rime under supercooled wet conditions. Plants that have evolved in warmer climates suffer damage when

4672-411: The rigging. Unlike hoar frost, which has a feathery appearance, rime generally has an icy, solid appearance. Black frost (or "killing frost") is not strictly speaking frost at all, because it is the condition seen in crops when the humidity is too low for frost to form, but the temperature falls so low that plant tissues freeze and die, becoming blackened, hence the term "black frost". Black frost often

4745-466: The scan can be evaluated to make sure there are no obvious glitches that skew the values. Because it may not be obvious to many users what each of the measurements really mean, a simulation tool allows a user to adjust key parameters, visualizing how surfaces which are obviously different to the human eye are differentiated by the measurements. For example, R a {\displaystyle Ra} fails to distinguish between two surfaces where one

4818-432: The solid surface on which they grow. The main difference between the ice coatings and frost spicules arises because the crystalline spicules grow directly from desublimation of water vapour from air, and desublimation is not a factor in icing of freezing surfaces. For desublimation to proceed, the surface must be below the frost point of the air, meaning that it is sufficiently cold for ice to form without passing through

4891-407: The surface itself is colder than freezing, ice will form on it. If the water deposits as a liquid that then freezes, it forms a coating that may look glassy, opaque, or crystalline, depending on its type. Depending on context, that process may also be called atmospheric icing . The ice it produces differs in some ways from crystalline frost, which consists of spicules of ice that typically project from

4964-414: The surface texture. From a mathematical perspective it is related to the spatial variability structure of surfaces, and inherently it is a multiscale property. It has different interpretations and definitions depending on the disciplines considered. Surface roughness , often shortened to roughness , is a component of surface finish (surface texture) . It is quantified by the deviations in the direction of

5037-432: The surface, snowflake-shaped crystals, or even large, knifelike blades of ice covering an object, which depends on many factors such as temperature, air pressure, air motion and turbulence, surface roughness and wettability , and the level of supersaturation. For example, water vapor adsorbs to glass very well, so automobile windows will often frost before the paint, and large hoar-frost crystals can grow very rapidly when

5110-526: The temperature falls after the Sun sets. In temperate climates , it most commonly appears on surfaces near the ground as fragile white crystals ; in cold climates, it occurs in a greater variety of forms. The propagation of crystal formation occurs by the process of nucleation , in specific, water nucleation , which is the same phenomenon responsible for the formation of clouds, fog, snow, rain and other meteorological phenomena. The ice crystals of frost form as

5183-421: The temperature falls low enough to freeze the water in the cells that make up the plant tissue . The tissue damage resulting from this process is known as "frost damage". Farmers in those regions where frost damage has been known to affect their crops often invest in substantial means to protect their crops from such damage. If a solid surface is chilled below the dew point of the surrounding humid air, and

5256-489: The texture of the frost crystals differs from the snow texture, and the dry crystals will not stick to fresh snow. Such conditions still prevent a strong bond between the snow layers. In very low temperatures where fluffy surface hoar crystals form without subsequently being covered with snow, strong winds may break them off, forming a dust of ice particles and blowing them over the surface. The ice dust then may form yukimarimo , as has been observed in parts of Antarctica, in

5329-428: The wind. Under suitable circumstances, objects cool to below the frost point of the surrounding air, well below the freezing point of water. Such freezing may be promoted by effects such as flood frost or frost pocket . These occur when ground-level radiation cools air until it flows downhill and accumulates in pockets of very cold air in valleys and hollows. Hoar frost may freeze in such low-lying cold air even when

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