Snow

For other use, see snow (disambiguation).

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Snow, a form of precipitation, is a crystalline form of water ice, consisting of a multitude of snowflakes. Since it is composed of small rough particles, it has an open and therefore soft structure, unless packed by external pressure. It is commonly formed when water vapor sublimates high in the atmosphere and then falls to the ground.

Snow fall varies by time and location, including geographic latitude, elevation and other factors which affect weather in general. In Southern latitudes, there is less chance of snow fall. Some mountains, even at or near the equator have permanent snow cover on their top.

Huge snow fall sometimes disrupts the social system of a modern city even in regions which are accustomed to them. Traffic may become jagged or even completely stop. Basic infrastructures such as supply of electrocity can be shut down. Snowday is a special sudden holiday due to that huge snow fall so that it becomes hard to commute to workplaces or attend schools.

Forms of recreation depending on snow:

• many winter sports
• playing with a sled
• making a stretch of snow icy to slide on
• building a snowman
• throwing snowballs mutually in a snowball fight or to others to tease them.

Where snow is scarce but the temperature low enough, snow cannons[?] may be used to produce an adequate amount for such sports.

Snow may be used as a construction material in, for example, Inuit snowhouses.

A snowflake is an aggregate of ice crystals that falls from a cloud.

The concept that no two snowflakes are alike is incorrect: in a volume of snow two feet square by ten inches deep there are roughly one million flakes, and so statistically many snowflakes must be visually identical. 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.

See also: snowman, sled, sleigh, ski, snowboard, frost, snowshoe, igloo, eskimo, Greenland.

External Links

• National Science Digital Library - Snowflake (http://www.nsdl.arm.gov/Library/glossary.shtml#snowflake)