Snow and Ski Forecasts
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Wikipedia-Article "Snow"
- For other uses, see Snow (disambiguation).
Snow is precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes. Since it is composed of small rough particles it is a granular material. It has an open and therefore soft structure, unless packed by external pressure.
Snow is commonly formed when water vapor undergoes deposition high in the atmosphere at a temperature of less than 0°C (32°F), and then falls to the ground.
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Types
- Flurries
- A very short snow storm, with a moderate to light amount of snow.
- Sleet
- Snow which has partially thawed while falling.
- Soft hail
- If this re-freezes on further descent, the resulting small icy pellets or granules of snow are called soft hail.
- Freezing rain
- A rainstorm, where the rain and ground are sufficiently cold that the raindrops freeze on impact. This can cover trees in a uniform layer of very clear, shiny ice, a beautiful phenomenon.
- Snow storm
- A long storm of relatively heavy snow.
- Snow squall
- A brief, very intense snowstorm.
- Blizzard
- A long-lasting snow storm with intense snowfall and usually high winds. Particularly severe storms can create whiteout conditions where visibility is reduced to less than 1 m.
- Snowdrifts
- Large piles of snow that occur near walls and curbs, as the wind tends to push the snow up toward the vertical surfaces.
- Ground blizzard
- Occurs when a strong wind drives already fallen snow to create drifts and whiteouts.
- Packing snow
- Snow that is at or near the melting point, so that it can easily be packed into snowballs and hurled at other people or objects.
- Slush
- Snow that has been melting for some time, to the point that it has become large, very cold puddles with chunks of snow and ice floating in them.
- Hail
- Many-layered ice balls, ranging from "popcorn" sized, to "nickel", "golf ball", "baseball" and "softball" sized hail.
- Hailstorm
- A storm of hail. If the hail is sufficiently large, it can cause damage to cars or even people.
- Artificial snow
- Snow can be also manufactured using snow cannons, which actually create tiny granules more like soft hail (this is sometimes called "grits" by those in the southern U.S. for its likeness to the texture of the food). In recent years, snow cannons have been produced that create more natural looking snow, but these machines are prohibitively expensive.
Occurrence
The probability of snowfall varies with season, location, and other geographic factors such as latitude and elevation. In the latitudinal area closer to the equator, there is a lesser chance of snowfall, 35° N and 40°S are often quoted as a rough delimiter. The western coasts of the major continents remain devoid of snow to much higher latitudes.
As temperature decreases with altitude, high mountains, even near the Equator, have permanent snow cover on their upper portions. Examples include Mount Kilimanjaro in Tanzania and the Tropical Andes in South America; however, the only snow actually to appear on the Equator is at the 4,690 m altitude of the southern slope of Volcán Cayambe in Ecuador (Google Earth images). Conversely, many regions of the Arctic and Antarctic receive very little precipitation and therefore experience little snow despite the bitter cold (below a certain temperature, air essentially loses its ability to retain water vapor).
Although the density of fresh snow widely varies, a general guideline is that the depth of snowfall is 10 times that of a rainfall containing an equivalent mass of water.
Substantial snowfall can, at times, even disrupt the infrastructure and services of a region that is accustomed to such weather. Automotive traffic may be greatly inhibited or may be stifled entirely. Basic infrastructures such as electricity, telephone lines, and gas supply can also be shut down. This can lead to a "snow day", which is a day on which the school or other services are cancelled due to unusually heavy snowfall. In areas that normally have very little snow, this may occur even with light accumulation — something often ridiculed by those people accustomed to colder climates, where streets would remain passable given the same amount of snow.
The highest seasonally cumulative precipitation of snow ever measured was on Mount Baker, Washington, U.S.A during the 1998–1999 season. Mount Baker received a staggering 28.96 meters (1,140 in) of snow, thus surpassing the previous record holder, Mount Rainier, Washington, U.S.A which during the 1971–1972 season received 28.5 meters (1,122 in) of snow.
See also: List of Countries receiving snowfall
Recreation
Forms of recreation dependent on snow:
- Many winter sports, such as skiing, snowmobiling, snowshoeing and snowboarding
- Playing with a sled or riding in a sleigh
- Building a snowman or snow fort
- Throwing snowballs mutually in a snowball fight or at others to tease them. (Humans seem to be the only animal that throw their snowballs. Pygmy chimpanzees have been known to carry snowballs around, but never to throw them.)
Where snow is scarce but the temperature is low enough, snow cannons may be used to produce an adequate amount for such sports.
The world´s biggest snowcastle is built in Kemi, Finland, every winter.
Geometry
A snowflake always has six lines of symmetry, which arises from the hexagonal crystal structure of ordinary ice (known as ice Ih) along its 'basal' plane.
There are, broadly, two possible explanations for the symmetry of snowflakes. Firstly, there could be communication (information transfer) between the arms, such that growth in each arm affects the growth in each other arm. Surface tension or phonons are among the ways that such communication could occur. The other explanation, which appears to be the prevalent view, is that the arms of a snowflake grow independently in an environment that is believed to be rapidly varying in temperature, humidity and so on. This environment is believed to be relatively spatially homogenous on the scale of a single flake, leading to the arms growing to a high level of visual similarity by responding in identical ways to identical conditions, much in the same way that unrelated trees respond to environmental changes by growing near-identical sets of tree rings. The difference in the environment in scales larger than a snowflake leads to the observed lack of correlation between the shapes of different snowflakes.
However, the concept that no two snowflakes are alike is incorrect; it is entirely possible, but unlikely, that a pair of snowflakes may be visually identical if their environments were similar enough, either because they grew very near one another, or simply by chance. The American Meteorological Society has reported that matching snow crystals were discovered by Nancy Knight of the National Center for Atmospheric Research. The crystals were not flakes in the usual sense but rather hollow hexagonal prisms.
- High-resolution gallery
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Media
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Snowing (info) |
| The video shows it snowing in a residential neighborhood | |
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See also
- Avalanche
- Sleigh
- Skiing
- Snow sculpture
- Snowball
- Snowboard
- Snowman
- Snow cannon
- Frost
- Snowshoe
- Snow removal
- Igloo
- Grit bin
- Lake effect snow
- List of countries receiving snowfall
- Eskimo words for snow
External links
