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Snowflake

March 06, 2023

For other uses, see Snowflake (disambiguation).

A snowflake is a single ice crystal that has achieved a sufficient size, and may have amalgamated with others, which falls through the Earth's atmosphere as snow.[1][2][3] Each flake nucleates around a dust particle in supersaturated air masses by attracting supercooled cloud water droplets, which freeze and accrete in crystal form. Complex shapes emerge as the flake moves through differing temperature and humidity zones in the atmosphere, such that individual snowflakes differ in detail from one another, but may be categorized in eight broad classifications and at least 80 individual variants. The main constituent shapes for ice crystals, from which combinations may occur, are needle, column, plate, and rime. Snow appears white in color despite being made of clear ice. This is due to diffuse reflection of the whole spectrum of light by the small crystal facets of the snowflakes.[4]

Freshly fallen snowflakes
Macro photography of natural snowflake

Formation

See also: Snow science
 
Naturally formed snowflakes differ from one another through happenstance of formation. The characteristic six branches is related with the crystal structure of ice.[5]

Snowflakes nucleate around mineral or organic particles in moisture-saturated, subfreezing air masses. They grow by net accretion to the incipient crystals in hexagonal formations. The cohesive forces are primarily electrostatic.

Nucleus

In warmer clouds, an aerosol particle or "ice nucleus" must be present in (or in contact with) the droplet to act as a nucleus. The particles that make ice nuclei are very rare compared to nuclei upon which liquid cloud droplets form; however, it is not understood what makes them efficient. Clays, desert dust, and biological particles may be effective,[6] although to what extent is unclear. Artificial nuclei include particles of silver iodide and dry ice, and these are used to stimulate precipitation in cloud seeding.[7] Experiments show that "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than −35 °C (−31 °F).[8]

Growth

 
Scanning electron microscope image of rime frost on both ends of a "capped column" snowflake.

Once a water droplet has frozen as an ice nucleus, it grows in a supersaturated environment—wherein liquid moisture coexists with ice beyond its equilibrium point at temperatures below the freezing. The droplet then grows by deposition 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 micrometers or millimeters in size at the expense of the water droplets. This process is known as the Wegener–Bergeron–Findeisen process. The corresponding depletion of water vapor causes the droplets to evaporate, meaning that 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 usually the type of ice particle that falls to the ground.[9] Guinness World Records lists the world's largest aggregated snowflakes as those of January 1887 at Fort Keogh, Montana, which were claimed to be 15 inches (38 cm) wide—well outside the normally documented range of aggregated flakes of three or four inches in width. Single crystals the size of a dime (17.91 mm in diameter) have been observed.[3] Snowflakes encapsulated in rime form balls known as graupel.

Appearance

Color

 
Snow crystals in strong direct sunlight act like small prisms

Although ice by itself is clear, snow usually appears white in color due to diffuse reflection of the whole spectrum of light by the scattering of light by the small crystal facets of the snowflakes of which it is comprised.[4]

Shape

The shape of the snowflake is determined broadly by the temperature and humidity at which it is formed.[9] Rarely, at a temperature of around −2 °C (28 °F), snowflakes can form in threefold symmetry — triangular snowflakes.[10] Most snow particles are irregular in form, despite their common depiction as symmetrical. It is unlikely that any two snowflakes are alike due to the estimated 1019 (10 quintillion) water molecules which make up a typical snowflake,[11] which grow 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.[12] Snowflakes that look identical, but may vary at the molecular level, have been grown under controlled conditions.[13]

Although snowflakes are never perfectly symmetrical, the growth of a non-aggregated snowflake often approximates six-fold radial symmetry, arising from the hexagonal crystalline structure of ice.[14] At that stage, the snowflake has the shape of a minute hexagon. The six "arms" of the snowflake, or dendrites, then grow independently from each of the corners of the hexagon, while either side of each arm grows independently. The microenvironment in which the snowflake grows changes dynamically as the snowflake falls through the cloud and tiny changes in temperature and humidity affect the way in which water molecules attach to the snowflake. Since the micro-environment (and its changes) are very nearly identical around the snowflake, each arm tends to grow in nearly the same way. However, being in the same micro-environment does not guarantee that each arm grows the same; indeed, for some crystal forms it does not because the underlying crystal growth mechanism also affects how fast each surface region of a crystal grows.[15] Empirical studies suggest less than 0.1% of snowflakes exhibit the ideal six-fold symmetric shape.[16] Very occasionally twelve branched snowflakes are observed; they maintain the six-fold symmetry.[17]

Classification

See also: Classifications of snow
 
An early classification of snowflakes by Israel Perkins Warren.[18]

Snowflakes form in a wide variety of intricate shapes, leading to the notion that "no two are alike". Although nearly-identical snowflakes have been made in laboratory, they are very unlikely to be found in nature.[19][11][20][21] Initial attempts to find identical snowflakes by photographing thousands of them with a microscope from 1885 onward by Wilson Alwyn Bentley found the wide variety of snowflakes we know about today.

Ukichiro Nakaya developed a crystal morphology diagram, relating crystal shape to the temperature and moisture conditions under which they formed, which is summarized in the following table:[22]

Crystal structure morphology as a function of temperature and water saturation
Temperature range Saturation range (g/m3) Types of snow crystal

below saturation

Types of snow crystal

above saturation

0 °C (32 °F) to −3.5 °C (26 °F) 0.0 to 0.5 Solid plates Thin plates

Dendrites

−3.5 °C (26 °F) to −10 °C (14 °F) 0.5 to 1.2 Solid prisms

Hollow prisms

Hollow prisms

Needles

−10 °C (14 °F) to −22 °C (−8 °F) 1.2 to 1.2 Thin plates

Solid plates

Sectored plates

Dendrites

−22 °C (−8 °F) to −40 °C (−40 °F) 0.0 to 0.4 Thin plates

Solid plates

Columns

Prisms

 
Wilson Bentley micrograph showing two classes of snowflake, plate and column. Missing is an example of a needle.

The shape of a snowflake is determined primarily by the temperature and humidity at which it is formed.[9] Freezing air down to −3 °C (27 °F) promotes planar crystals (thin and flat). In colder air down to −8 °C (18 °F), the crystals form as hollow columns, prisms or needles. In air as cold as −22 °C (−8 °F), shapes become plate-like again, often with branched or dendritic features. At temperatures below −22 °C (−8 °F), the crystals become plate-like or columnar, depending on the degree of saturation. As Nakaya discovered, shape is also a function of whether the prevalent moisture is above or below saturation. Forms below the saturation line trend more towards solid and compact. Crystals formed in supersaturated air trend more towards lacy, delicate and ornate. Many more complex growth patterns also form such as side-planes, bullet-rosettes and also planar types depending on the conditions and ice nuclei.[23][24][25] If a crystal has started forming in a column growth regime, at around −5 °C (23 °F), 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".[9]

Magono and Lee devised a classification of freshly formed snow crystals that includes 80 distinct shapes. They are listed in the following main categories (with symbol):[26]

  • Needle crystal (N) – Subdivided into: Simple and combination of needles
  • Columnar crystal (C) – Subdivided into: Simple and combination of columns
  • Plate crystal (P) – Subdivided into: Regular crystal in one plane, plane crystal with extensions, crystal with irregular number of branches, crystal with 12 branches, malformed crystal, radiating assemblage of plane branches
  • Combination of columnar and plate crystals (CP) – Subdivided into: Column with plane crystal at both ends, bullet with plane crystals, plane crystal with spatial extensions at ends
  • Columnar crystal with extended side planes (S) – Subdivided into: Side planes, scalelike side planes, combination of side planes, bullets, and columns
  • Rimed crystal (R) – Subdivided into: Rimed crystal, densely rimed crystal, graupellike crystal, graupel
  • Irregular snow crystal (I) – Subdivided into: Ice particle, rimed particle, broken piece from a crystal, miscellaneous
  • Germ of snow crystal (G) – Subdivided into: Minute column, germ of skeleton form, minute hexagonal plate, minute stellar crystal, minute assemblage of plates, irregular germ

They documented each with micrographs.

The International Classification for Seasonal Snow on the Ground describes snow crystal classification, once it is deposited on the ground, that include grain shape and grain size. The system also characterizes the snowpack, as the individual crystals metamorphize and coalesce.[27]

Use as a symbol

 
Snowflake in the coat of arms of Lumijoki

The snowflake is often a traditional seasonal image or motif used around the Christmas season, especially in Europe and North America. As a Christian celebration, Christmas celebrates the incarnation of Jesus, who according to Christian belief atones for the sins of humanity; so, in European and North American Christmas traditions, snowflakes symbolize purity.[28][29] Snowflakes are also traditionally associated with the "White Christmas" weather that often occurs during Christmastide.[29] During this period, it is quite popular to make paper snowflakes by folding a piece of paper several times, cutting out a pattern with scissors and then unfolding it.[30][31] The Book of Isaiah refers to the atonement of sins causing them to appear "white as snow" before God (cf. Isaiah 1:18);[29]

Snowflakes are also often used as symbols representing winter or cold conditions. For example, snow tires which enhance traction during harsh winter driving conditions are labelled with a snowflake on the mountain symbol.[32] A stylized snowflake has been part of the emblem of the 1968 Winter Olympics, 1972 Winter Olympics, 1984 Winter Olympics, 1988 Winter Olympics, 1998 Winter Olympics and 2002 Winter Olympics.[33][34]

 
The three grades in the Order of Canada (Companion, Officer and Member, respectively) .

A six pointed stylized hexagonal snowflake used for the Order of Canada (a national honor system ) has come to symbolize Canadians northern heritage and diversity.[35]

In heraldry, the snowflake is a stylized charge. Three different snowflake symbols are encoded in Unicode: "snowflake" at U+2744 (❄); "tight trifoliate snowflake" at U+2745 (❅); and "heavy chevron snowflake" at U+2746 (❆).

Gallery

A selection of photographs taken by Wilson Bentley (1865–1931):

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See also

References

  1. ^ Knight, C.; Knight, N. (1973). Snow crystals. Scientific American, vol. 228, no. 1, pp. 100–107.
  2. ^ Hobbs, P.V. 1974. Ice Physics. Oxford: Clarendon Press.
  3. ^ a b Broad, William J. (2007-03-20). "Giant Snowflakes as Big as Frisbees? Could Be". The New York Times. from the original on 2011-11-04. Retrieved 2009-07-12.
  4. ^ a b Lawson, Jennifer E. (2001). "Chapter 5: The Colors of Light". Hands-on Science: Light, Physical Science (matter). Portage & Main Press. p. 39. ISBN 978-1-894110-63-1. from the original on 2014-01-01. Retrieved 2009-06-28.
  5. ^ Physics of Ice, V. F. Petrenko, R. W. Whitworth, Oxford University Press, 1999, ISBN 9780198518945
  6. ^ Christner, Brent Q.; Morris, Cindy E.; Foreman, Christine M.; Cai, Rongman & Sands, David C. (2007). "Ubiquity of Biological Ice Nucleators in Snowfall". Science. 319 (5867): 1214. Bibcode:2008Sci...319.1214C. CiteSeerX 10.1.1.395.4918. doi:10.1126/science.1149757. PMID 18309078. S2CID 39398426.
  7. ^ "Meteorology Glossary: Cloud seeding". American Meteorological Society. 26 January 2012. from the original on 22 December 2015. Retrieved 2016-01-05.
  8. ^ Basil John Mason (1971). Physics of Clouds. Clarendon. ISBN 978-0-19-851603-3.
  9. ^ a b c d M. Klesius (2007). "The Mystery of Snowflakes". National Geographic. 211 (1): 20. ISSN 0027-9358.
  10. ^ Libbrecht, Kenneth G. (2006-09-11). "Guide to Snowflakes". California Institute of Technology. from the original on 2009-07-10. Retrieved 2009-06-28.
  11. ^ a b John Roach (2007-02-13). ""No Two Snowflakes the Same" Likely True, Research Reveals". National Geographic News. from the original on 2010-01-09. Retrieved 2009-07-14.
  12. ^ Libbrecht, Kenneth (Winter 2004–2005). "Snowflake Science" (PDF). American Educator. (PDF) from the original on 2010-09-17. Retrieved 2010-10-19.
  13. ^ Olsen, Erik (16 February 2018). "Meet the scientist who makes identical snowflakes". Quartz. Retrieved 16 February 2018.
  14. ^ Nelson, Jon (15 March 2011). "The Six-fold Nature of Snow". The Story of Snow. from the original on 9 December 2017.
  15. ^ Nelson, Jon (17 March 2005). "Branch Growth and Sidebranching in Snow Crystals" (PDF). Story of Snow. (PDF) from the original on 5 January 2015.
  16. ^ Bohannon, John (10 April 2013). "ScienceShot: The True Shape of Snowflakes". ScienceNOW. American Association for the Advancement of Science. from the original on 29 October 2016. Retrieved 5 January 2016.
  17. ^ Smalley, I.J. (1963). "Symmetry of Snow Crystals". Nature. 198 (4885): 1080–1081. Bibcode:1963Natur.198.1080S. doi:10.1038/1981080b0. S2CID 4186179.
  18. ^ Warren, Israel Perkins (1863). Snowflakes: a chapter from the book of nature. Boston: American Tract Society. p. 164. Retrieved 2016-11-25.
  19. ^ Kenneth G. Libbrecht. "Identical-Twin Snowflakes".
  20. ^ Jon Nelson (2008-09-26). "Origin of diversity in falling snow" (PDF). Atmospheric Chemistry and Physics. 8 (18): 5669–5682. Bibcode:2008ACP.....8.5669N. doi:10.5194/acp-8-5669-2008. (PDF) from the original on 2011-11-20. Retrieved 2011-08-30.
  21. ^ Libbrecht, Kenneth (Winter 2004–2005). (PDF). American Educator. Archived from the original (PDF) on 2008-11-28. Retrieved 2009-07-14.
  22. ^ Bishop, Michael P.; Björnsson, Helgi; Haeberli, Wilfried; Oerlemans, Johannes; Shroder, John F.; Tranter, Martyn (2011). Singh, Vijay P.; Singh, Pratap; Haritashya, Umesh K. (eds.). Encyclopedia of Snow, Ice and Glaciers. Springer Science & Business Media. p. 1253. ISBN 978-90-481-2641-5.
  23. ^ Matthew Bailey; John Hallett (2004). "Growth rates and habits of ice crystals between −20 and −70C". Journal of the Atmospheric Sciences. 61 (5): 514–544. Bibcode:2004JAtS...61..514B. doi:10.1175/1520-0469(2004)061<0514:GRAHOI>2.0.CO;2.
  24. ^ Kenneth G. Libbrecht (2006-10-23). "A Snowflake Primer". California Institute of Technology. from the original on 2009-07-10. Retrieved 2009-06-28.
  25. ^ Kenneth G. Libbrecht (January–February 2007). "The Formation of Snow Crystals". American Scientist. 95 (1): 52–59. doi:10.1511/2007.63.52.
  26. ^ Magono, Choji; Lee, Chung Woo (1966). "Meteorological Classification of Natural Snow Crystals". Journal of the Faculty of Science. 7 (Geophysics ed.). Hokkaido. 3 (4): 321–335. hdl:2115/8672.
  27. ^ Fierz, C.; Armstrong, R.L.; Durand, Y.; Etchevers, P.; Greene, E.; et al. (2009), The International Classification for Seasonal Snow on the Ground (PDF), IHP-VII Technical Documents in Hydrology, vol. 83, Paris: UNESCO, p. 80, (PDF) from the original on 2016-09-29, retrieved 2016-11-25
  28. ^ Wallach, Jennifer Jensen; Swindall, Lindsey R.; Wise, Michael D. (12 February 2016). The Routledge History of American Foodways. Routledge. p. 223. ISBN 978-1-317-97522-9.
  29. ^ a b c Mosteller, Angie (2008). Christmas. Itasca Books. p. 147. ISBN 978-1-60791-008-4.
  30. ^ for detailed instructions see for example this page 2012-01-08 at the Wayback Machine
  31. ^ Other instructions and pictures of paper snowflakes 2013-02-08 at the Wayback Machine
  32. ^ Gilles, Tim (2004). Automotive chassis. Cengage Learning. p. 271. ISBN 978-1-4018-5630-4.
  33. ^ "More About Sapporo 1972: The Emblem". International Olympic Committee. from the original on 2016-02-09. Retrieved 2016-01-05.
  34. ^ "Olympic Games Salt Lake City 2002 – The emblem". International Olympic Committee. 2009. from the original on 2009-03-25. Retrieved 2009-07-15.
  35. ^ "Canadian Honours > Order of Canada > Levels and Insignia". The Governor General of Canada. 2002.

Further reading

External links

 
Wikimedia Commons has media related to Snowflakes.

March 06, 2023
snowflake, other, uses, disambiguation, snowflake, single, crystal, that, achieved, sufficient, size, have, amalgamated, with, others, which, falls, through, earth, atmosphere, snow, each, flake, nucleates, around, dust, particle, supersaturated, masses, attra. For other uses see Snowflake disambiguation A snowflake is a single ice crystal that has achieved a sufficient size and may have amalgamated with others which falls through the Earth s atmosphere as snow 1 2 3 Each flake nucleates around a dust particle in supersaturated air masses by attracting supercooled cloud water droplets which freeze and accrete in crystal form Complex shapes emerge as the flake moves through differing temperature and humidity zones in the atmosphere such that individual snowflakes differ in detail from one another but may be categorized in eight broad classifications and at least 80 individual variants The main constituent shapes for ice crystals from which combinations may occur are needle column plate and rime Snow appears white in color despite being made of clear ice This is due to diffuse reflection of the whole spectrum of light by the small crystal facets of the snowflakes 4 Freshly fallen snowflakes Macro photography of natural snowflake Contents 1 Formation 1 1 Nucleus 1 2 Growth 1 3 Appearance 1 3 1 Color 1 3 2 Shape 2 Classification 3 Use as a symbol 4 Gallery 5 See also 6 References 7 Further reading 8 External linksFormation EditSee also Snow science Naturally formed snowflakes differ from one another through happenstance of formation The characteristic six branches is related with the crystal structure of ice 5 Snowflakes nucleate around mineral or organic particles in moisture saturated subfreezing air masses They grow by net accretion to the incipient crystals in hexagonal formations The cohesive forces are primarily electrostatic Nucleus Edit In warmer clouds an aerosol particle or ice nucleus must be present in or in contact with the droplet to act as a nucleus The particles that make ice nuclei are very rare compared to nuclei upon which liquid cloud droplets form however it is not understood what makes them efficient Clays desert dust and biological particles may be effective 6 although to what extent is unclear Artificial nuclei include particles of silver iodide and dry ice and these are used to stimulate precipitation in cloud seeding 7 Experiments show that homogeneous nucleation of cloud droplets only occurs at temperatures lower than 35 C 31 F 8 Growth Edit Scanning electron microscope image of rime frost on both ends of a capped column snowflake Once a water droplet has frozen as an ice nucleus it grows in a supersaturated environment wherein liquid moisture coexists with ice beyond its equilibrium point at temperatures below the freezing The droplet then grows by deposition 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 micrometers or millimeters in size at the expense of the water droplets This process is known as the Wegener Bergeron Findeisen process The corresponding depletion of water vapor causes the droplets to evaporate meaning that 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 usually the type of ice particle that falls to the ground 9 Guinness World Records lists the world s largest aggregated snowflakes as those of January 1887 at Fort Keogh Montana which were claimed to be 15 inches 38 cm wide well outside the normally documented range of aggregated flakes of three or four inches in width Single crystals the size of a dime 17 91 mm in diameter have been observed 3 Snowflakes encapsulated in rime form balls known as graupel Appearance Edit Color Edit Snow crystals in strong direct sunlight act like small prisms Although ice by itself is clear snow usually appears white in color due to diffuse reflection of the whole spectrum of light by the scattering of light by the small crystal facets of the snowflakes of which it is comprised 4 Shape Edit The shape of the snowflake is determined broadly by the temperature and humidity at which it is formed 9 Rarely at a temperature of around 2 C 28 F snowflakes can form in threefold symmetry triangular snowflakes 10 Most snow particles are irregular in form despite their common depiction as symmetrical It is unlikely that any two snowflakes are alike due to the estimated 1019 10 quintillion water molecules which make up a typical snowflake 11 which grow 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 12 Snowflakes that look identical but may vary at the molecular level have been grown under controlled conditions 13 Although snowflakes are never perfectly symmetrical the growth of a non aggregated snowflake often approximates six fold radial symmetry arising from the hexagonal crystalline structure of ice 14 At that stage the snowflake has the shape of a minute hexagon The six arms of the snowflake or dendrites then grow independently from each of the corners of the hexagon while either side of each arm grows independently The microenvironment in which the snowflake grows changes dynamically as the snowflake falls through the cloud and tiny changes in temperature and humidity affect the way in which water molecules attach to the snowflake Since the micro environment and its changes are very nearly identical around the snowflake each arm tends to grow in nearly the same way However being in the same micro environment does not guarantee that each arm grows the same indeed for some crystal forms it does not because the underlying crystal growth mechanism also affects how fast each surface region of a crystal grows 15 Empirical studies suggest less than 0 1 of snowflakes exhibit the ideal six fold symmetric shape 16 Very occasionally twelve branched snowflakes are observed they maintain the six fold symmetry 17 Classification EditSee also Classifications of snow An early classification of snowflakes by Israel Perkins Warren 18 Snowflakes form in a wide variety of intricate shapes leading to the notion that no two are alike Although nearly identical snowflakes have been made in laboratory they are very unlikely to be found in nature 19 11 20 21 Initial attempts to find identical snowflakes by photographing thousands of them with a microscope from 1885 onward by Wilson Alwyn Bentley found the wide variety of snowflakes we know about today Ukichiro Nakaya developed a crystal morphology diagram relating crystal shape to the temperature and moisture conditions under which they formed which is summarized in the following table 22 Crystal structure morphology as a function of temperature and water saturation Temperature range Saturation range g m3 Types of snow crystal below saturation Types of snow crystal above saturation0 C 32 F to 3 5 C 26 F 0 0 to 0 5 Solid plates Thin plates Dendrites 3 5 C 26 F to 10 C 14 F 0 5 to 1 2 Solid prisms Hollow prisms Hollow prisms Needles 10 C 14 F to 22 C 8 F 1 2 to 1 2 Thin plates Solid plates Sectored plates Dendrites 22 C 8 F to 40 C 40 F 0 0 to 0 4 Thin plates Solid plates Columns Prisms Wilson Bentley micrograph showing two classes of snowflake plate and column Missing is an example of a needle The shape of a snowflake is determined primarily by the temperature and humidity at which it is formed 9 Freezing air down to 3 C 27 F promotes planar crystals thin and flat In colder air down to 8 C 18 F the crystals form as hollow columns prisms or needles In air as cold as 22 C 8 F shapes become plate like again often with branched or dendritic features At temperatures below 22 C 8 F the crystals become plate like or columnar depending on the degree of saturation As Nakaya discovered shape is also a function of whether the prevalent moisture is above or below saturation Forms below the saturation line trend more towards solid and compact Crystals formed in supersaturated air trend more towards lacy delicate and ornate Many more complex growth patterns also form such as side planes bullet rosettes and also planar types depending on the conditions and ice nuclei 23 24 25 If a crystal has started forming in a column growth regime at around 5 C 23 F 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 9 Magono and Lee devised a classification of freshly formed snow crystals that includes 80 distinct shapes They are listed in the following main categories with symbol 26 Needle crystal N Subdivided into Simple and combination of needles Columnar crystal C Subdivided into Simple and combination of columns Plate crystal P Subdivided into Regular crystal in one plane plane crystal with extensions crystal with irregular number of branches crystal with 12 branches malformed crystal radiating assemblage of plane branches Combination of columnar and plate crystals CP Subdivided into Column with plane crystal at both ends bullet with plane crystals plane crystal with spatial extensions at ends Columnar crystal with extended side planes S Subdivided into Side planes scalelike side planes combination of side planes bullets and columns Rimed crystal R Subdivided into Rimed crystal densely rimed crystal graupellike crystal graupel Irregular snow crystal I Subdivided into Ice particle rimed particle broken piece from a crystal miscellaneous Germ of snow crystal G Subdivided into Minute column germ of skeleton form minute hexagonal plate minute stellar crystal minute assemblage of plates irregular germThey documented each with micrographs The International Classification for Seasonal Snow on the Ground describes snow crystal classification once it is deposited on the ground that include grain shape and grain size The system also characterizes the snowpack as the individual crystals metamorphize and coalesce 27 Use as a symbol Edit Snowflake in the coat of arms of Lumijoki The snowflake is often a traditional seasonal image or motif used around the Christmas season especially in Europe and North America As a Christian celebration Christmas celebrates the incarnation of Jesus who according to Christian belief atones for the sins of humanity so in European and North American Christmas traditions snowflakes symbolize purity 28 29 Snowflakes are also traditionally associated with the White Christmas weather that often occurs during Christmastide 29 During this period it is quite popular to make paper snowflakes by folding a piece of paper several times cutting out a pattern with scissors and then unfolding it 30 31 The Book of Isaiah refers to the atonement of sins causing them to appear white as snow before God cf Isaiah 1 18 29 Snowflakes are also often used as symbols representing winter or cold conditions For example snow tires which enhance traction during harsh winter driving conditions are labelled with a snowflake on the mountain symbol 32 A stylized snowflake has been part of the emblem of the 1968 Winter Olympics 1972 Winter Olympics 1984 Winter Olympics 1988 Winter Olympics 1998 Winter Olympics and 2002 Winter Olympics 33 34 The three grades in the Order of Canada Companion Officer and Member respectively A six pointed stylized hexagonal snowflake used for the Order of Canada a national honor system has come to symbolize Canadians northern heritage and diversity 35 In heraldry the snowflake is a stylized charge Three different snowflake symbols are encoded in Unicode snowflake at U 2744 tight trifoliate snowflake at U 2745 and heavy chevron snowflake at U 2746 Gallery EditA selection of photographs taken by Wilson Bentley 1865 1931 See also EditKoch snowflake Mathematical curve resembling a snowflake Sekka Zusetsu Guide to snowflake forms written in Japan in the 19th century Selburose An eight pointed floral design that may be mistaken for a snowflake Timeline of snowflake researchReferences Edit Knight C Knight N 1973 Snow crystals Scientific American vol 228 no 1 pp 100 107 Hobbs P V 1974 Ice Physics Oxford Clarendon Press a b Broad William J 2007 03 20 Giant Snowflakes as Big as Frisbees Could Be The New York Times Archived from the original on 2011 11 04 Retrieved 2009 07 12 a b Lawson Jennifer E 2001 Chapter 5 The Colors of Light Hands on Science Light Physical Science matter Portage amp Main Press p 39 ISBN 978 1 894110 63 1 Archived from the original on 2014 01 01 Retrieved 2009 06 28 Physics of Ice V F Petrenko R W Whitworth Oxford University Press 1999 ISBN 9780198518945 Christner Brent Q Morris Cindy E Foreman Christine M Cai Rongman amp Sands David C 2007 Ubiquity of Biological Ice Nucleators in Snowfall Science 319 5867 1214 Bibcode 2008Sci 319 1214C CiteSeerX 10 1 1 395 4918 doi 10 1126 science 1149757 PMID 18309078 S2CID 39398426 Meteorology Glossary Cloud seeding American Meteorological Society 26 January 2012 Archived from the original on 22 December 2015 Retrieved 2016 01 05 Basil John Mason 1971 Physics of Clouds Clarendon ISBN 978 0 19 851603 3 a b c d M Klesius 2007 The Mystery of Snowflakes National Geographic 211 1 20 ISSN 0027 9358 Libbrecht Kenneth G 2006 09 11 Guide to Snowflakes California Institute of Technology Archived from the original on 2009 07 10 Retrieved 2009 06 28 a b John Roach 2007 02 13 No Two Snowflakes the Same Likely True Research Reveals National Geographic News Archived from the original on 2010 01 09 Retrieved 2009 07 14 Libbrecht Kenneth Winter 2004 2005 Snowflake Science PDF American Educator Archived PDF from the original on 2010 09 17 Retrieved 2010 10 19 Olsen Erik 16 February 2018 Meet the scientist who makes identical snowflakes Quartz Retrieved 16 February 2018 Nelson Jon 15 March 2011 The Six fold Nature of Snow The Story of Snow Archived from the original on 9 December 2017 Nelson Jon 17 March 2005 Branch Growth and Sidebranching in Snow Crystals PDF Story of Snow Archived PDF from the original on 5 January 2015 Bohannon John 10 April 2013 ScienceShot The True Shape of Snowflakes ScienceNOW American Association for the Advancement of Science Archived from the original on 29 October 2016 Retrieved 5 January 2016 Smalley I J 1963 Symmetry of Snow Crystals Nature 198 4885 1080 1081 Bibcode 1963Natur 198 1080S doi 10 1038 1981080b0 S2CID 4186179 Warren Israel Perkins 1863 Snowflakes a chapter from the book of nature Boston American Tract Society p 164 Retrieved 2016 11 25 Kenneth G Libbrecht Identical Twin Snowflakes Jon Nelson 2008 09 26 Origin of diversity in falling snow PDF Atmospheric Chemistry and Physics 8 18 5669 5682 Bibcode 2008ACP 8 5669N doi 10 5194 acp 8 5669 2008 Archived PDF from the original on 2011 11 20 Retrieved 2011 08 30 Libbrecht Kenneth Winter 2004 2005 Snowflake Science PDF American Educator Archived from the original PDF on 2008 11 28 Retrieved 2009 07 14 Bishop Michael P Bjornsson Helgi Haeberli Wilfried Oerlemans Johannes Shroder John F Tranter Martyn 2011 Singh Vijay P Singh Pratap Haritashya Umesh K eds Encyclopedia of Snow Ice and Glaciers Springer Science amp Business Media p 1253 ISBN 978 90 481 2641 5 Matthew Bailey John Hallett 2004 Growth rates and habits of ice crystals between 20 and 70C Journal of the Atmospheric Sciences 61 5 514 544 Bibcode 2004JAtS 61 514B doi 10 1175 1520 0469 2004 061 lt 0514 GRAHOI gt 2 0 CO 2 Kenneth G Libbrecht 2006 10 23 A Snowflake Primer California Institute of Technology Archived from the original on 2009 07 10 Retrieved 2009 06 28 Kenneth G Libbrecht January February 2007 The Formation of Snow Crystals American Scientist 95 1 52 59 doi 10 1511 2007 63 52 Magono Choji Lee Chung Woo 1966 Meteorological Classification of Natural Snow Crystals Journal of the Faculty of Science 7 Geophysics ed Hokkaido 3 4 321 335 hdl 2115 8672 Fierz C Armstrong R L Durand Y Etchevers P Greene E et al 2009 The International Classification for Seasonal Snow on the Ground PDF IHP VII Technical Documents in Hydrology vol 83 Paris UNESCO p 80 archived PDF from the original on 2016 09 29 retrieved 2016 11 25 Wallach Jennifer Jensen Swindall Lindsey R Wise Michael D 12 February 2016 The Routledge History of American Foodways Routledge p 223 ISBN 978 1 317 97522 9 a b c Mosteller Angie 2008 Christmas Itasca Books p 147 ISBN 978 1 60791 008 4 for detailed instructions see for example this page Archived 2012 01 08 at the Wayback Machine Other instructions and pictures of paper snowflakes Archived 2013 02 08 at the Wayback Machine Gilles Tim 2004 Automotive chassis Cengage Learning p 271 ISBN 978 1 4018 5630 4 More About Sapporo 1972 The Emblem International Olympic Committee Archived from the original on 2016 02 09 Retrieved 2016 01 05 Olympic Games Salt Lake City 2002 The emblem International Olympic Committee 2009 Archived from the original on 2009 03 25 Retrieved 2009 07 15 Canadian Honours gt Order of Canada gt Levels and Insignia The Governor General of Canada 2002 Further reading EditKenneth G Libbrecht 2006 Ken Libbrecht s Field Guide to Snowflakes Voyageur Press ISBN 978 0 7603 2645 9 External links Edit Wikimedia Commons has media related to Snowflakes California Institute of Technology professor Kenneth G Libbrecht information on the parameters of snowflake formation Overview Online guide to snowflakes and ice crystals Interview with video Retrieved from https en wikipedia org w index php title Snowflake amp oldid 1141574608 Use as a symbol, wikipedia, wiki, book, books, library,

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