Snow

Snow

Overview
Snow is a form of precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 within the Earth's atmosphere in the form of crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

line water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

, consisting of a multitude of snowflake
Snowflake
Snowflakes are conglomerations of frozen ice crystals which fall through the Earth's atmosphere. They begin as snow crystals which develop when microscopic supercooled cloud droplets freeze. Snowflakes come in a variety of sizes and shapes. Complex shapes emerge as the flake moves through...

s that fall from cloud
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...

s. Since snow is composed of small ice particles, it is a granular material
Granular material
A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact . The constituents that compose granular material must be large enough such that they are not subject to thermal motion fluctuations...

. It has an open and therefore soft structure, unless packed by external pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

. Snowflakes come in a variety of sizes and shapes. Types which fall in the form of a ball due to melting and refreezing, rather than a flake, are known as graupel, ice pellets or snow grains
Snow grains
Snow grains are a form of precipitation characterized as:*white, opaque grains of ice*very small Snow grains are a form of precipitation characterized as:*white, opaque grains of ice*very small...

.
Discussion
Ask a question about 'Snow'
Start a new discussion about 'Snow'
Answer questions from other users
Full Discussion Forum
 
Recent Discussions
Encyclopedia
Snow is a form of precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 within the Earth's atmosphere in the form of crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

line water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

, consisting of a multitude of snowflake
Snowflake
Snowflakes are conglomerations of frozen ice crystals which fall through the Earth's atmosphere. They begin as snow crystals which develop when microscopic supercooled cloud droplets freeze. Snowflakes come in a variety of sizes and shapes. Complex shapes emerge as the flake moves through...

s that fall from cloud
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...

s. Since snow is composed of small ice particles, it is a granular material
Granular material
A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact . The constituents that compose granular material must be large enough such that they are not subject to thermal motion fluctuations...

. It has an open and therefore soft structure, unless packed by external pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

. Snowflakes come in a variety of sizes and shapes. Types which fall in the form of a ball due to melting and refreezing, rather than a flake, are known as graupel, ice pellets or snow grains
Snow grains
Snow grains are a form of precipitation characterized as:*white, opaque grains of ice*very small Snow grains are a form of precipitation characterized as:*white, opaque grains of ice*very small...

. Snowfall amount and its related liquid equivalent precipitation amount are determined using a variety of different rain gauge
Rain gauge
A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time....

s.

The process of precipitating snow is called snowfall. Snowfall tends to form within regions of upward motion of air around a type of low-pressure system known as an extratropical cyclone
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...

. Snow can fall poleward of these systems' associated warm front
Warm front
A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient...

s and within their comma head precipitation patterns (called such due to the comma-like shape of the cloud and precipitation pattern around the poleward and west sides of extratropical cyclones). Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow
Thundersnow
Thundersnow, also known as a winter thunderstorm or a thunder snowstorm, is a relatively rare kind of thunderstorm with snow falling as the primary precipitation instead of rain. It typically falls in regions of strong upward motion within the cold sector of an extratropical cyclone...

 is possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy snow is possible where upslope flow is maximized within windward sides of the terrain at elevation, if the atmosphere is cold enough.

Forms


Once on the ground, snow can be categorized as powdery when fluffy, granular when it begins the cycle of melting and refreezing, and eventually ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 once it packs down, after multiple melting and refreezing cycles, into a dense mass called snow pack. When powdery, snow moves with the wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

 from the location where it originally landed, forming deposits called snowdrift
Snowdrift
A snowdrift is a deposit of snow sculpted by wind into a mound during a snowstorm. Snowdrifts resemble sand dunes and are formed in a similar manner, namely, by wind moving light snow and depositing it when the wind is slowed, usually against a stationary object. Snow normally crests and slopes...

s which may have a depth of several meters. After attaching to hillsides, blown snow can evolve into a snow slab, which is an avalanche
Avalanche
An avalanche is a sudden rapid flow of snow down a slope, occurring when either natural triggers or human activity causes a critical escalating transition from the slow equilibrium evolution of the snow pack. Typically occurring in mountainous terrain, an avalanche can mix air and water with the...

 hazard on steep slopes. The existence of a snowpack keeps temperatures colder than they would be otherwise, as the whiteness of the snow reflects most sunlight, and the absorbed heat goes into melting the snow rather than increasing its temperature. The water equivalent of snowfall is measured to monitor how much liquid is available to flood river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

s from meltwater
Meltwater
Meltwater is the water released by the melting of snow or ice, including glacial ice and ice shelfs over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing...

 which will occur during the following spring
Spring (season)
Spring is one of the four temperate seasons, the transition period between winter and summer. Spring and "springtime" refer to the season, and broadly to ideas of rebirth, renewal and regrowth. The specific definition of the exact timing of "spring" varies according to local climate, cultures and...

. Snow cover can protect crops from extreme cold. If snowfall stays on the ground for a series of years uninterrupted, the snowpack develops into a mass of ice called glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

. Fresh snow absorbs sound, lowering ambient noise over a landscape
Landscape
Landscape comprises the visible features of an area of land, including the physical elements of landforms such as mountains, hills, water bodies such as rivers, lakes, ponds and the sea, living elements of land cover including indigenous vegetation, human elements including different forms of...

 because the trapped air between snowflakes attenuates vibration. These acoustic qualities quickly minimize and reverse, once a layer of freezing rain
Freezing rain
Freezing rain is the name given to rain that falls when surface temperatures are below freezing. The raindrops become supercooled while passing through a sub-freezing layer of air, many hundred feet , just above the surface, and then freeze upon impact with any object they encounter. The resulting...

 falls on top of snow cover. Walking across snowfall produces a squeaking sound at low temperatures.

The energy balance of the snowpack itself is dictated by several heat exchange processes. The snowpack absorbs solar shortwave radiation that is partially blocked by cloud cover and reflected by snow surface. A long-wave heat exchange takes place between the snowpack and its surrounding environment that includes overlying air mass, tree cover and clouds. Heat exchange takes place by convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....

 between the snowpack and the overlaying air mass, and it is governed by the temperature gradient and wind speed. Moisture exchange between the snowpack and the overlying air mass is accompanied with latent heat transfer that is influenced by vapor pressure gradient and air wind. Rain on snow can add significant amounts of thermal energy to the snowpack. A generally insignificant heat exchange takes place by conduction
Heat conduction
In heat transfer, conduction is a mode of transfer of energy within and between bodies of matter, due to a temperature gradient. Conduction means collisional and diffusive transfer of kinetic energy of particles of ponderable matter . Conduction takes place in all forms of ponderable matter, viz....

 between the snowpack and the ground. The small temperature change from before to after a snowfall is a result of the heat transfer between the snowpack and the air.

The term snow storm can describe a heavy snowfall while a blizzard
Blizzard
A blizzard is a severe snowstorm characterized by strong winds. By definition, the difference between blizzard and a snowstorm is the strength of the wind. To be a blizzard, a snow storm must have winds in excess of with blowing or drifting snow which reduces visibility to 400 meters or ¼ mile or...

involves snow and wind, obscuring visibility. Snow shower is a term for an intermittent snowfall, while flurry
Snow flurry
A snow flurry is a brief instance of light snow, with very little or no accumulation of snow on the ground.-External links:* *...

is used for very light, brief snowfalls. Snow can fall more than a meter at a time during a single storm in flat areas, and meters at a time in rugged terrain, such as mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

s. When snow falls in significant quantities, travel by foot, car, airplane and other means becomes highly restricted, but other methods of mobility become possible: the use of snowmobile
Snowmobile
A snowmobile, also known in some places as a snowmachine, or sled,is a land vehicle for winter travel on snow. Designed to be operated on snow and ice, they require no road or trail. Design variations enable some machines to operate in deep snow or forests; most are used on open terrain, including...

s, snowshoe
Snowshoe
A snowshoe is footwear for walking over the snow. Snowshoes work by distributing the weight of the person over a larger area so that the person's foot does not sink completely into the snow, a quality called "flotation"....

s and ski
Ski
A ski is a long, flat device worn on the foot, usually attached through a boot, designed to help the wearer slide smoothly over snow. Originally intended as an aid to travel in snowy regions, they are now mainly used for recreational and sporting purposes...

s. When heavy snow occurs early in the fall (or, on rarer occasions, late in the spring
Spring (season)
Spring is one of the four temperate seasons, the transition period between winter and summer. Spring and "springtime" refer to the season, and broadly to ideas of rebirth, renewal and regrowth. The specific definition of the exact timing of "spring" varies according to local climate, cultures and...

), significant damage occurs to trees still in leaf. Areas with significant snow each year can store the winter snow within an ice house, which can be used to cool structures during the following summer
Summer
Summer is the warmest of the four temperate seasons, between spring and autumn. At the summer solstice, the days are longest and the nights are shortest, with day-length decreasing as the season progresses after the solstice...

. A variation on snow has been observed on Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, though composed of metallic compounds and occurring at a substantially higher temperature.

Cause




Extratropical cyclone
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...

s can bring cold and dangerous conditions with heavy rain and snow with winds exceeding 119 km/h (73.9 mph), (sometimes referred to as windstorms
European windstorm
A European windstorm is a severe cyclonic windstorm associated with areas of low atmospheric pressure that track across the North Atlantic towards northwestern Europe. They are most common in the winter months...

 in Europe). The band of precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 that is associated with their warm front
Warm front
A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient...

 is often extensive, forced by weak upward vertical motion of air over the frontal boundary which condenses
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

 as it cools off and produces precipitation within an elongated band, which is wide and stratiform, meaning falling out of nimbostratus clouds. When moist air tries to dislodge an arctic air mass, overrunning snow can result within the poleward side of the elongated precipitation band
Rainband
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as...

. In the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

, poleward is towards the North Pole
North Pole
The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets its surface...

, or north. Within the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

, poleward is towards the South Pole
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...

, or south.

Within the cold sector, poleward and west of the cyclone center, small scale
Microscale meteorology
Microscale meteorology is the study of short-lived atmospheric phenomena smaller than mesoscale, about 1 km or less. These two branches of meteorology are sometimes grouped together as "mesoscale and microscale meteorology" and together study all phenomena smaller than synoptic scale; that is they...

 or mesoscale
Mesoscale meteorology
Mesoscale meteorology is the study of weather systems smaller than synoptic scale systems but larger than microscale and storm-scale cumulus systems. Horizontal dimensions generally range from around 5 kilometers to several hundred kilometers...

 bands of heavy snow can occur within a cyclone's comma head pattern. The cyclone's comma head pattern is a comma-shaped area of clouds and precipitation found around mature extratropical cyclones. These snow bands typically have a width of sp=us 20 to sp=us 50. These bands in the comma head are associated with areas of frontogenesis
Frontogenesis
Frontogenesis, in meteorology, refers to the formation or strengthening of an atmospheric front. During frontogenesis, the temperature gradient tightens and as a result the thermal wind becomes imbalanced. To maintain balance, the geostrophic wind aloft and below adjust, such that regions of...

, or zones of strengthening temperature contrast.


Southwest of extratropical cyclones, curved cyclonic flow bringing cold air across the relatively warm water bodies can lead to narrow lake-effect snow bands. Those bands bring strong localized snowfall which can be understood as follows: Large water bodies such as lakes efficiently store heat that results in significant temperature differences (larger than 13 °C or 23 °F) between the water surface and the air above. Because of this temperature difference, warmth and moisture are transported upward, condensing into vertically oriented clouds (see satellite picture) which produce snow showers. The temperature decrease with height and cloud depth are directly affected by both the water temperature and the large-scale environment. The stronger the temperature decrease with height, the deeper the clouds get, and the greater the precipitation rate becomes.

In mountainous areas, heavy snowfall accumulates when air is forced to ascend the mountains and squeeze out precipitation along their windward slopes, which in cold conditions, falls in the form of snow. Because of the ruggedness of terrain, forecasting the location of heavy snowfall remains a significant challenge.

Snowflakes


Snow crystals form when tiny supercooled cloud droplets (about 10 μm in diameter) freeze
Freezing
Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

. These droplets are able to remain liquid at temperatures lower than -18 °C, because to freeze, a few molecules in the droplet need to get together by chance to form an arrangement similar to that in an ice lattice; then the droplet freezes around this "nucleus." Experiments show that this "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than -35 °C. In warmer clouds an aerosol particle or "ice nucleus" must be present in (or in contact with) the droplet to act as a nucleus. Ice nuclei are very rare compared to that cloud condensation nuclei on which liquid droplets form. Clays, desert dust and biological particles may be effective, although to what extent is unclear. Artificial nuclei include particles of silver iodide
Silver iodide
Silver iodide is a yellow, inorganic, photosensitive iodide of silver used in photography, in medicine as an antiseptic, and in rainmaking for cloud seeding.-Crystal structure:...

 and dry ice
Dry ice
Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...

, and these are used to stimulate precipitation in cloud seeding
Cloud seeding
Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud...

.

Once a droplet has frozen, it grows in the supersaturated environment, which is one where air is saturated with respect to ice when the temperature is below the freezing point. The droplet then grows by diffusion of water molecules in the air (vapor) onto the ice crystal surface where they are collected. Because water droplets are so much more numerous than the ice crystals due to their sheer abundance, the crystals are able to grow to hundreds of micrometer
Micrometer
A micrometer , sometimes known as a micrometer screw gauge, is a device incorporating a calibrated screw used widely for precise measurement of small distances in mechanical engineering and machining as well as most mechanical trades, along with other metrological instruments such as dial, vernier,...

s or millimeters in size at the expense of the water droplets by a process known as the Wegner-Bergeron-Findeison process. The corresponding depletion of water vapor causes the ice crystals grow at the droplets' expense. These large crystals are an efficient source of precipitation, since they fall through the atmosphere due to their mass, and may collide and stick together in clusters, or aggregates. These aggregates are snowflakes, and are usually the type of ice particle that falls to the ground. Guinness World Records list the world's largest snowflakes as those of January 1887 at Fort Keogh, Montana; allegedly one measured 38 cm (15 in) wide. Although the ice is clear, scattering of light by the crystal facets and hollows/imperfections mean that the crystals often appear white in color due to diffuse reflection
Diffuse reflection
Diffuse reflection is the reflection of light from a surface such that an incident ray is reflected at many angles rather than at just one angle as in the case of specular reflection...

 of the whole spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...

 of light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

 by the small ice particles.

The shape of the snowflake is determined broadly by the temperature and humidity at which it is formed. The most common snow particles are visibly irregular. Planar crystals (thin and flat) grow in air between 0 °C (32 °F) and -3 C. Between -3 C and -8 C, the crystals will form needles or hollow columns or prisms (long thin pencil-like shapes). From -8 C to -22 C the shape reverts back to plate-like, often with branched or dendritic features. At temperatures below -22 C, the crystal development becomes column-like, although many more complex growth patterns also form such as side-planes, bullet-rosettes and also planar types depending on the conditions and ice nuclei. If a crystal has started forming in a column growth regime, at around -5 C, and then falls into the warmer plate-like regime, then plate or dendritic crystals sprout at the end of the column, producing so called "capped columns."

A snowflake consists of roughly 1019 water molecules, which are added to its core at different rates and in different patterns, depending on the changing temperature and humidity within the atmosphere that the snowflake falls through on its way to the ground. As a result, it is extremely difficult to encounter two identical snowflakes. Initial attempts to find identical snowflakes by photographing
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...

 thousands their images under a microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 from 1885 onward by Wilson Alwyn Bentley
Wilson Bentley
Wilson Alwyn "Snowflake" Bentley , born in Jericho, Vermont, United States is one of the first known photographers of snowflakes. He perfected a process of catching flakes on black velvet in such a way that their images could be captured before they either melted or sublimed.-Biography:Bentley was...

 found the wide variety of snowflakes we know about today. It is more likely that two snowflakes could become virtually identical if their environments were similar enough. Matching snow crystals were discovered in Wisconsin in 1988. The crystals were not flakes in the usual sense but rather hollow hexagonal prisms
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...

.

Types




Types of snow
Types of snow
Types of snow can be designated by the shape of its flakes, description of how it is falling, and by how it collects on the ground. A blizzard and snow storm indicate heavy snowfalls over a large area, snow squalls give heavy snowfalls over narrow bands, while flurries are used for the lightest...

 can be designated by the shape of the flakes, the rate of accumulation, and the way the snow collects on the ground. Types which fall in the form of a ball due to melting and refreezing cycles, rather than a flake, are known as graupel, with ice pellets and snow pellets as types of graupel associated with wintry precipitation. Once on the ground, snow can be categorized as powdery when fluffy, granular when it begins the cycle of melting and refreezing, and eventually ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

once it packs down into a dense drift after multiple melting and refreezing cycles. When powdery, snow drifts with the wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

 from the location where it originally fell, forming deposits with a depth of several meters in isolated locations. Snow fence
Snow fence
A snow fence is a structure, similar to a sand fence, that forces drifting snow to accumulate in a desired place. They are primarily employed to minimize the amount of snowdrift on roadways and railways. Farmers and ranchers may use temporary snow fences to create large drifts in basins for a...

s are constructed in order to help control snow drifting in the vicinity of roads, to improve highway
Highway
A highway is any public road. In American English, the term is common and almost always designates major roads. In British English, the term designates any road open to the public. Any interconnected set of highways can be variously referred to as a "highway system", a "highway network", or a...

 safety. After attaching to hillsides, blown snow can evolve into a snow slab, which is an avalanche hazard on steep slopes. A frozen equivalent of dew
Dew
[Image:Dew on a flower.jpg|right|220px|thumb|Some dew on an iris in Sequoia National Park]]Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening...

 known as hoar frost forms on a snow pack when winds are light and there is ample low-level moisture over the snow pack.

Snowfall's intensity is determined by visibility
Visibility
In meteorology, visibility is a measure of the distance at which an object or light can be clearly discerned. It is reported within surface weather observations and METAR code either in meters or statute miles, depending upon the country. Visibility affects all forms of traffic: roads, sailing...

. When the visibility is over sp=us 1, snow is considered light. Moderate snow describes snowfall with visibility restrictions between 0.5 and 1 km. Heavy snowfall describes conditions when visibility is less than 0.5 km. Steady snows of significant intensity are often referred to as "snowstorms". When snow is of variable intensity and short duration, it is described as a "snow shower". The term snow flurry
Snow flurry
A snow flurry is a brief instance of light snow, with very little or no accumulation of snow on the ground.-External links:* *...

 is used to describe the lightest form of a snow shower.

A blizzard
Blizzard
A blizzard is a severe snowstorm characterized by strong winds. By definition, the difference between blizzard and a snowstorm is the strength of the wind. To be a blizzard, a snow storm must have winds in excess of with blowing or drifting snow which reduces visibility to 400 meters or ¼ mile or...

 is a weather condition involving snow which has varying definitions in different parts of the world. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, a blizzard is occurring when two conditions are met for a period of three hours or more: A sustained wind or frequent gusts to sp=us 35, and sufficient snow in the air to reduce visibility to less than sp=us 0.4. In Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, the criteria are similar. While heavy snowfall often occurs during blizzard conditions, falling snow is not a requirement, as blowing snow
Blowing snow
Blowing snow is snow lifted from the surface by the wind, at a height of 8 feet or more, that will reduce visibility. Blowing snow can come from falling snow or snow that already accumulated on the ground but is picked up and blown about by strong winds. It is one of the classic requirements for a...

 can create a ground blizzard
Ground blizzard
Ground blizzard refers to a weather condition where loose snow or ice on the ground is lifted and blown by strong winds. The primary difference between a ground blizzard as opposed to a regular blizzard is that in a ground blizzard no precipitation is produced at the time, but rather all the...

.

Density




Snow remains on the ground until it melts
Melting
Melting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid...

 or sublimates. Sublimation of snow directly into water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...

 is most likely to occur on a dry and windy day such as when a strong downslope wind, such as a Chinook wind
Chinook wind
Chinook winds , often called chinooks, commonly refers to foehn winds in the interior West of North America, where the Canadian Prairies and Great Plains meet various mountain ranges, although the original usage is in reference to wet, warm coastal winds in the Pacific Northwest.Chinook is claimed...

, exists. The water equivalent of a given amount of snow is the depth of a layer of water having the same mass and upper area. For example, if the snow covering a given area has a water equivalent of sp=us 50, then it will melt into a pool of water sp=us 50 deep covering the same area. This is a much more useful measurement to hydrologists
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

 than snow depth, as the density of cool freshly fallen snow widely varies. New snow commonly has a density of around 8% of water. This means that sp=us 33 of snow melts down to sp=us 2.5 of water. Cloud temperatures and physical processes in the cloud affect the shape of individual snow crystals. Highly branched or dendritic crystals tend to have more space between the arms of ice that form the snowflake and this snow will therefore have a lower density, often referred to as "dry" snow. Conditions that create columnar or plate-like crystals will have much less air space within the crystal and will therefore be denser and feel "wetter".

Once the snow is on the ground, it will settle under its own weight (largely due to differential evaporation) until its density is approximately 30% of water. Increases in density above this initial compression occur primarily by melting and refreezing, caused by temperatures above freezing or by direct solar radiation. In colder climates, snow lies on the ground all winter. By late spring, snow densities typically reach a maximum of 50% of water. When the snow does not all melt in the summer it evolves into firn
Firn
Firn is partially-compacted névé, a type of snow that has been left over from past seasons and has been recrystallized into a substance denser than névé. It is ice that is at an intermediate stage between snow and glacial ice...

, where individual granules become more spherical in nature, evolving into a glacier as the ice flows downhill.

Acoustic properties



Under water, snowfall has a unique sound when compared to other forms of precipitation. Despite the different sizes and shapes on individual snowflakes, the sound made when individual flakes fall upon the surface of a freshwater lake are quite similar. On the ground, newly fallen snow acts as a sound-absorbing material, which minimizes sound over its surface. This is due to the trapped air between the individual crystalline flakes which act to trap sound waves and dampen vibrations. Once it is blown around by the wind and exposed to sunshine, snow hardens and its sound-softening quality diminishes. Snow cover as thin as 2 centimetre (0.78740157480315 in) thick changes the acoustic properties of a landscape. Studies concerning the acoustic
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...

 properties of snow have revealed that loud sounds, such as from a pistol
Handgun
A handgun is a firearm designed to be held and operated by one hand. This characteristic differentiates handguns as a general class of firearms from long guns such as rifles and shotguns ....

, can be used to measure snow cover permeability and depth. Within motion pictures, the sound of walking through snow is simulated using cornstarch, salt, or cat litter. When the temperature falls below -10 C, snow will squeak when walked upon due to the crushing of the ice crystals within the snow. If covered by a layer of freezing rain
Freezing rain
Freezing rain is the name given to rain that falls when surface temperatures are below freezing. The raindrops become supercooled while passing through a sub-freezing layer of air, many hundred feet , just above the surface, and then freeze upon impact with any object they encounter. The resulting...

, the hardened frozen surface acts to echo sounds, similar to concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

.

Snowfall measurement


The liquid equivalent of snowfall may be evaluated using a snow gauge
Snow gauge
A snow gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of solid precipitation over a set period of time....

 or with a standard rain gauge
Rain gauge
A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time....

 having a diameter of 100 mm (4 in; plastic) or 200 mm (8 in; metal). Rain gauges are adjusted to winter by removing the funnel and inner cylinder and allowing the snow/freezing rain to collect inside the outer cylinder. Antifreeze
Antifreeze
Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....

 liquid may be added to melt the snow or ice that falls into the gauge. In both types of gauges once the snowfall/ice is finished accumulating, or as its height in the gauge approaches 300 mm (11.8 in), the snow is melted and the water amount recorded.

Another type of gauge used to measure the liquid equivalent of snowfall is the weighing precipitation gauge. The wedge and tipping bucket gauges will have problems with snow measurement. Attempts to compensate for snow/ice by warming the tipping bucket meet with limited success, since snow may sublimate if the gauge is kept much above the freezing temperature. Weighing gauges with antifreeze should do fine with snow, but again, the funnel needs to be removed before the event begins. At some automatic weather station
Automatic weather station
An automatic weather station is an automated version of the traditional weather station, either to save human labour or to enable measurements from remote areas...

s an ultrasonic snow depth sensor may be used to augment the precipitation gauge.

Spring snow melt is a major source of water supply to areas in temperate zones near mountains that catch and hold winter snow, especially those with a prolonged dry summer
Mediterranean climate
A Mediterranean climate is the climate typical of most of the lands in the Mediterranean Basin, and is a particular variety of subtropical climate...

. In such places, water equivalent is of great interest to water managers wishing to predict spring runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

 and the water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...

 of cities downstream. Measurements are made manually at marked locations known as snow courses, and remotely using special scales called snow pillows
Snow pillow
A snow pillow is a device for measuring snowpack, especially for automated reporting stations such as SNOTEL.The snow pillow measures the water equivalent of the snow pack based on hydrostatic pressure created by overlying snow...

. Snow stakes and simple rulers can be used to determine the depth of the snow pack, though they will not evaluate either its density or liquid equivalent.

When a snow measurement is made, various networks exist across the United States and elsewhere where rainfall measurements can be submitted through the Internet, such as CoCoRAHS
Community Collaborative Rain, Hail and Snow network
The Community Collaborative Rain, Hail and Snow Network, or CoCoRaHS, is a network of volunteer weather watchers who take daily readings of precipitation, and report them online or by phone.-History:...

 or GLOBE. If a network is not available in the area where one lives, the nearest local weather office will likely be interested in the measurement.

Records


The world record for the highest seasonal total snowfall was measured in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 at Mount Baker Ski Area
Mount Baker Ski Area
Mt. Baker Ski Area is a ski resort located in Whatcom County, Washington, United States at the end of State Route 542. The base elevation is at 3,500 feet , while the peak of the resort is at 5,089 feet ....

, outside of the town Bellingham
Bellingham, Washington
Bellingham is the largest city in, and the county seat of, Whatcom County in the U.S. state of Washington. It is the twelfth-largest city in the state. Situated on Bellingham Bay, Bellingham is protected by Lummi Island, Portage Island, and the Lummi Peninsula, and opens onto the Strait of Georgia...

, Washington during the 1998–1999 season. Mount Baker received 2896 cm (1,140.2 in) of snow, thus surpassing the previous record holder, Mount Rainier
Mount Rainier
Mount Rainier is a massive stratovolcano located southeast of Seattle in the state of Washington, United States. It is the most topographically prominent mountain in the contiguous United States and the Cascade Volcanic Arc, with a summit elevation of . Mt. Rainier is considered one of the most...

, Washington, which during the 1971–1972 season received 2850 cm (1,122 in) of snow.

The largest known piece of ice to fall to earth was an ice block 6 meters (20 ft) across that fell in Scotland on 13 August 1849.

Snow blindness




Fresh snow reflects 90% or more of ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 radiation that causes snow blindness
Snow blindness
Photokeratitis or ultraviolet keratitis is a painful eye condition caused by exposure of insufficiently protected eyes to the ultraviolet rays from either natural or artificial sources. Photokeratitis is akin to a sunburn of the cornea and conjunctiva, and is not usually noticed until several...

 and reduces absorption of sunlight by the ground.Snow blindness
Snow blindness
Photokeratitis or ultraviolet keratitis is a painful eye condition caused by exposure of insufficiently protected eyes to the ultraviolet rays from either natural or artificial sources. Photokeratitis is akin to a sunburn of the cornea and conjunctiva, and is not usually noticed until several...

 (also known as ultraviolet keratitis
Keratitis
Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...

, photokeratitis or niphablepsia) is a painful eye condition, caused by exposure of unprotected eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

s to the ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 (UV) rays in bright sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

 reflected
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...

 from snow or ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

. This condition is a problem in polar regions and at high altitudes, as with every sp=us 1000 of elevation (above sea level), the intensity of UV rays increases by 4%. Snow's large reflection of light makes night skies much brighter, since reflected light is directed back up into the sky. However, when there is also cloud
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...

 cover, light is then reflected back to the ground. This greatly amplifies light emitted from city lights, causing the 'bright night' effect. A similar brightening effect occurs when no snow is falling and there is a full moon and a large amount of snow.

Relation to river flow


Many rivers originating in mountainous or high-latitude regions receive a significant portion of their flow from snowmelt. This often makes the river's flow highly seasonal resulting in periodic flooding during the spring months and at least in dry mountainous regions like the mountain West of the US or most of Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

 and Afghanistan
Afghanistan
Afghanistan , officially the Islamic Republic of Afghanistan, is a landlocked country located in the centre of Asia, forming South Asia, Central Asia and the Middle East. With a population of about 29 million, it has an area of , making it the 42nd most populous and 41st largest nation in the world...

, very low flow for the rest of the year. In contrast, if much of the melt is from glaciated or nearly glaciated areas, the melt continues through the warm season, with peak flows occurring in mid to late summer.

Effects on human society



Substantial snowfall can disrupt public infrastructure and services, slowing human activity even in regions that are accustomed to such weather. Air and ground transport may be greatly inhibited or shut down entirely. Populations living in snow-prone areas have developed various ways to travel across the snow, such as ski
Ski
A ski is a long, flat device worn on the foot, usually attached through a boot, designed to help the wearer slide smoothly over snow. Originally intended as an aid to travel in snowy regions, they are now mainly used for recreational and sporting purposes...

s, snowshoe
Snowshoe
A snowshoe is footwear for walking over the snow. Snowshoes work by distributing the weight of the person over a larger area so that the person's foot does not sink completely into the snow, a quality called "flotation"....

s, and sled
Sled
A sled, sledge, or sleigh is a land vehicle with a smooth underside or possessing a separate body supported by two or more smooth, relatively narrow, longitudinal runners that travels by sliding across a surface. Most sleds are used on surfaces with low friction, such as snow or ice. In some cases,...

s pulled by horses, dogs, or other animals and later, snowmobile
Snowmobile
A snowmobile, also known in some places as a snowmachine, or sled,is a land vehicle for winter travel on snow. Designed to be operated on snow and ice, they require no road or trail. Design variations enable some machines to operate in deep snow or forests; most are used on open terrain, including...

s. Basic utilities such as electricity
Electricity distribution
File:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity distribution from generation stations to consumers...

, telephone line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...

s, and gas supply can also fail. In addition, snow can make roads much harder to travel and vehicles attempting to use them can easily become stuck.

The combined effects can lead to a "snow day
Weather-related cancellation
A weather-related cancellation or delay is when an institution, operation, or event is closed, canceled, or delayed as a result of inclement weather conditions...

" on which gatherings such as school or work are officially canceled. In areas that normally have very little or no snow, a snow day may occur when there is only light accumulation or even the threat of snowfall, since those areas are unprepared to handle any amount of snow. In some areas, such as some states in the United States, schools are given a yearly quota of snow days (or "calamity days"). Once the quota is exceeded, the snow days must be made up. In other states, all snow days must be made up. For example, schools may extend the remaining school days later into the afternoon, shorten spring break
Spring break
Spring break – also known as March break, Study week or Reading week in the United Kingdom and some parts of Canada – is a recess in early spring at universities and schools in the United States, Canada, mainland China, Korea, Japan, Taiwan, Mexico, the Dominican Republic, the United...

, or delay the start of summer vacation
Summer vacation
Summer vacation is a vacation in the summertime between school years in which students and instructors are off school typically between 6 and 12 weeks, depending on the country and district.-Students:In some countries, students participate in programs such as organized sports, summer camps, and...

.

Accumulated snow is removed
Snow removal
Snow removal is the job of removing snow after a snowfall to make travel easier and safer. This is done by both individual households and by governments and institutions.-De-icing and anti-icing:...

 to make travel easier and safer, and to decrease the long-term impact of a heavy snowfall. This process utilizes shovel
Shovel
A shovel is a tool for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore. Shovels are extremely common tools that are used extensively in agriculture, construction, and gardening....

s and snowplow
Snowplow
A snowplow is a device intended for mounting on a vehicle, used for removing snow and ice from outdoor surfaces, typically those serving transportation purposes...

s, and is often assisted by sprinkling salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 or other chloride-based chemicals, which reduce the melting temperature of snow. In some areas with abundant snowfall, such as Yamagata Prefecture
Yamagata Prefecture
-Fruit:Yamagata Prefecture is the largest producer of cherries and pears in Japan. A large quantity of other kinds of fruits such as grapes, apples, peaches, melons, persimmons and watermelons are also produced.- Demographics :...

, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, people harvest snow and store it surrounded by insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...

 in ice houses. This allows the snow to be used through the summer for refrigeration and air conditioning, which requires far less electricity than traditional cooling methods.

Agriculture


Snowfall can be beneficial to agriculture by serving as a thermal insulator
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...

, conserving the heat of the Earth and protecting crops
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 from subfreezing weather. Some agricultural areas depend on an accumulation of snow during winter that will melt gradually in spring, providing water for crop growth. If it melts into water and refreezes upon sensitive crops, such as oranges, the resulting ice will protect the fruit from exposure to lower temperatures.

Recreation



Many winter sports, such as skiing
Skiing
Skiing is a recreational activity using skis as equipment for traveling over snow. Skis are used in conjunction with boots that connect to the ski with use of a binding....

, snowboarding
Snowboarding
Snowboarding is a sport that involves descending a slope that is covered with snow on a snowboard attached to a rider's feet using a special boot set onto mounted binding. The development of snowboarding was inspired by skateboarding, sledding, surfing and skiing. It was developed in the U.S.A...

, snowmobiling, and snowshoe
Snowshoe
A snowshoe is footwear for walking over the snow. Snowshoes work by distributing the weight of the person over a larger area so that the person's foot does not sink completely into the snow, a quality called "flotation"....

ing depend upon snow. Where snow is scarce but the temperature is low enough, snow cannons may be used to produce an adequate amount for such sports. Children and adults can play on a sled
Sled
A sled, sledge, or sleigh is a land vehicle with a smooth underside or possessing a separate body supported by two or more smooth, relatively narrow, longitudinal runners that travels by sliding across a surface. Most sleds are used on surfaces with low friction, such as snow or ice. In some cases,...

 or ride in a sleigh. Although a person's footsteps remain a visible lifeline within a snow-covered landscape, snow cover is considered a general danger to hiking since the snow obscures landmarks and makes the landscape itself appear uniform.
One of the recognizable recreational uses of snow is in building snowmen. A snowman is created by making a man shaped figure out of snow – often using a large, shaped snowball for the body and a smaller snowball for the head which is often decorated with simple household items – traditionally including a carrot
Carrot
The carrot is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh...

 for a nose, and coal for eyes, nose and mouth; occasionally including old clothes such as a top hat
Top hat
A top hat, beaver hat, high hat silk hat, cylinder hat, chimney pot hat or stove pipe hat is a tall, flat-crowned, broad-brimmed hat, predominantly worn from the latter part of the 18th to the middle of the 20th century...

 or scarf.

Snow can be used to make snow cone
Snow cone
Snow cones or snow balls are a variation of the shaved ice dessert commonly served throughout North America in paper cones or styrofoam cups...

s, also known as snowballs, which are usually eaten in the summer months. Flat areas of snow can be used to make snow angel
Snow angel
A snow angel is a human-made depression formed in an area of snow in the shape of an angel. Making snow angels is a common childhood game.-Technique:...

s, a popular pastime for children.

Snow can be used to alter the format of outdoor games such as Capture the flag
Capture the flag
Capture the Flag is a traditional outdoor sport generally played by children, where two teams each have a flag and the objective is to capture the other team's flag, located at the team's "base," and bring it safely back to their own base...

, or for snowball fights. The world's biggest snowcastle, the SnowCastle of Kemi, is built in Kemi
Kemi
Kemi is a town and municipality of Finland. It is located very near the city of Tornio. It was founded in 1869 by royal decree, because of its proximity to a deep water harbour....

, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 every winter. Since 1928 Michigan Technological University
Michigan Technological University
Michigan Technological University is a public research university located in Houghton, Michigan, United States. Its main campus sits on on a bluff overlooking Portage Lake...

 in Houghton, Michigan
Houghton, Michigan
Houghton is a city in the U.S. state of Michigan's Upper Peninsula and largest city in the Copper Country on the Keweenaw Peninsula. As of the 2010 census, the city population was 7,708. It is the county seat of Houghton County...

 has held an annual Winter Carnival
Michigan Technological University's Winter Carnival
Michigan Technological University's Winter Carnival is an annual celebration that takes place every winter in Houghton, Michigan. It is a time to celebrate the large amounts of snowfall Michigan's Upper Peninsula receives each winter...

 in mid-February, during which a large Snow Sculpture Contest
Snow sculpture
Snow sculpture is a sculpture form comparable to sand sculpture or ice sculpture in that most of it is now practiced outdoors, and often in full view of spectators, thus giving it kinship to performance art in the eyes of some. The materials and the tools differ widely, but often include hand...

 takes place between various clubs, fraternities, and organizations in the community and the university. Each year there is a central theme, and prizes are awarded based on creativity. Snowball softball tournaments are held in snowy areas, usually using a bright orange softball for visibility, and burlap sacks filled with snow for the bases.

Damage




When heavy, wet snow with a snow-water equivalent (SWE) ratio of between 6:1 and 12:1 (in extreme cases, as heavy as 4:1) and a weight in excess of 10 pounds per square foot (~50 kg/m2) piles onto trees or electricity lines – particularly if the trees have full leaves or are not adapted to snow – significant damage may occur on a scale usually associated with hurricanes. An avalanche can occur upon a sudden thermal or mechanical impact upon snow that has accumulated on a mountain, which causes the snow to rush downhill en masse. Preceding an avalanche is a phenomenon known as an avalanche wind caused by the approaching avalanche itself, which adds to its destructive potential. Large amounts of snow which accumulate on top of man-made structures can lead to structural failure. During snowmelt, acidic precipitation which previously fell into the snow pack is released, which harms marine life.

Design of structures considering snow load


The design of all structures and buildings use the ground snow load to some extent by professional engineers and designers. In North America, the northern states will be designed to accommodate the live load design contributed by the ground snow load in a pounds per square foot (PSF) loading analysis. This load is typically the governing design factor on roofs and structural elements exposed to the effects of snow. Closer to the Equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

, the snow load becomes less of a factor and snow may or may not be the governing factor. Ground snow in North America is provided by the American Society of Civil Engineers (ASCE7-latest edition) for most jurisdictions.

Extraterrestrial snow


Very light snow is known to occur at high latitudes on Mars. A "snow" of hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

s is also theorized to occur on Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...

's moon Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....

.

While there is little or no water on Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, there is a phenomenon which is quite similar to snow. The Magellan probe
Magellan probe
The Magellan spacecraft, also referred to as the Venus Radar Mapper, was a 1,035-kilogram robotic space probe launched by NASA on May 4, 1989, to map the surface of Venus using Synthetic Aperture Radar and measure the planetary gravity...

 imaged a highly reflective substance at the tops of Venus's highest mountain peaks which bore a strong resemblance to terrestrial snow. This substance arguably formed from a similar process to snow, albeit at a far higher temperature. Too volatile to condense on the surface, it rose in gas form to cooler higher elevations, where it then fell as precipitation. The identity of this substance is not known with certainty, but speculation has ranged from elemental tellurium to lead sulfide (galena
Galena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...

).

See also


  • 2007 Siberian orange snow
    2007 Siberian orange snow
    The 2007 Siberian orange snow was an anomalous phenomenon that occurred on Friday, February 2, 2007 when an orange-tinted snow fell across an area of in Omsk Oblast, Siberian Federal District, Russia, as well as into the neighbouring oblasts of Tomsk and Tyumen...

  • Alberta clipper
    Alberta clipper
    An Alberta clipper is a fast moving low pressure area which generally affects the central provinces of Canada and parts of the Upper Midwest and Great Lakes regions of the United States. Most clippers occur between December and February, but can also occur occasionally in the month of November...

  • Animal tracks
    Animal tracks
    Animal tracks are the imprints left behind in soil, snow, mud, or other ground surfaces that an animal walk across. Animal tracks are used by hunters in tracking their prey and by naturalists to identify animals living in a given area....

  • Black ice
    Black ice
    Black ice, sometimes called glare ice or clear ice, refers to a thin coating of glazed ice on a surface.While not truly black, it is virtually transparent, allowing black asphalt/macadam roadways to be seen through it, hence the term "black ice"...

  • Cold wave
    Cold wave
    A cold wave is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24 hour period requiring substantially increased protection to agriculture, industry, commerce, and...

  • Eskimo words for snow
    Eskimo words for snow
    The "Eskimo words for snow" claim is a widespread misconception alleging that Eskimos have an unusually large number of words for snow. In fact, the Eskimo–Aleut languages have about the same number of distinct word roots referring to snow as English does...

  • Frost
    Frost
    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. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...

  • Grit bin
    Grit bin
    A grit bin or salt bin is an item of street furniture, commonly found in countries where freezing temperatures and snowfall occur, which holds a mixture of salt and grit which is spread over roads if they have snow or ice on them...

  • Heikki Lunta
    Heikki Lunta
    Heikki Lunta is the embodiment of the Finnish snow god character, who originated in the mythology of the Upper Peninsula of Michigan.The character of Heikki Lunta is a product of the heavy Finnish-American presence in Michigan's Upper Peninsula combined with a tremendous annual...

  • Igloo
    Igloo
    An igloo or snowhouse is a type of shelter built of snow, originally built by the Inuit....

  • Knickerbocker Storm
    Knickerbocker Storm
    The Knickerbocker Storm was a blizzard that occurred on January 27–28, 1922 in the upper South and middle Atlantic United States. The storm took its name from the resulting collapse of the Knickerbocker Theatre in Washington, D.C. shortly after 9 p.m...

  • Quinzhee
    Quinzhee
    A quinzhee or quinzee is a shelter made by hollowing out a pile of settled snow. This is in contrast to an igloo, which is made from blocks of hard snow...

  • Snow cave
    Snow cave
    A snow cave is a shelter constructed in snow by certain animals in the wild, human mountain climbers, winter recreational enthusiasts, and winter survivalists. It has thermal properties similar to an Igloo and is particularly effective at providing protection from wind as well as low temperatures...

  • Snow farming
    Snow farming
    Snow farming is the use of obstacles, equipment and knowledge about management of snow in order to strategically manipulate snow coverage. Often this is done for the purpose of skiing or even preventing snow drift in certain areas like roads...

  • Snowbelt
    Snowbelt
    Snowbelt is a term describing of a number of regions near the Great Lakes in North America where heavy snowfall in the form of lake-effect snow is particularly common. Snowbelts are typically found downwind of the lakes, principally off the eastern and southern shores...

  • The wrong type of snow
  • Timeline of snowflake research
    Timeline of snowflake research
    The hexagonal snowflake, a crystalline formation of ice, has intrigued people throughout history. This is a chronology of interest and research into snowflakes...

  • Ukichiro Nakaya
    Ukichiro Nakaya
    was a Japanese physicist and science essayist known for his work in glaciology and low-temperature sciences. He is credited with making the first artificial snowflakes.-Life and research:...



External links