Editing Snow (section)

==Effects on civilization==
Snow routinely affects civilization in four major areas: transportation, agriculture, structures, and sports. Most transportation modes are impeded by snow on the travel surface. Agriculture often relies on snow as a source of seasonal moisture. Structures may fail under snow loads. Humans find a wide variety of recreational activities in snowy landscapes. It also affects the conduct of warfare.

===Transportation===
{{See also|Snowplow}}
Snow affects the rights of way of highways, airfields and railroads. The [[snowplow]] is common to all workers, though roadways take anti-icing chemicals to prevent bonding of ice and airfields may not; railroads rely on abrasives for track traction.

====Highway====
[[File:Cars covered in Snow on Lake Shore Drive Chicago Feb 2 2011 storm.JPG|thumb|Traffic stranded in a [[2011 Groundhog Day blizzard|2011 Chicago snowstorm]].]]
[[File:Snowy Higddhway 4012.jpg|thumb|Reduced visibility on [[Ontario Highway 401]] in Toronto due to a [[snowsquall]].]]
In the late 20th century, an estimated $2 billion was spent annually in North America on roadway winter maintenance, owing to snow and other winter weather events, according to a 1994 report by Kuemmel. The study surveyed the practices of jurisdictions within 44 US states and nine Canadian provinces. It assessed the policies, practices, and equipment used for winter maintenance. It found similar practices and progress to be prevalent in Europe.<ref name = Kuemmel/>

The dominant effect of snow on vehicle contact with the road is diminished friction. This can be improved with the use of [[snow tire]]s, which have a tread designed to compact snow in a manner that enhances traction. The key to maintaining a roadway that can accommodate traffic during and after a snow event is an effective anti-icing program that employs both chemicals and [[Snowplow|plowing]].<ref name = Kuemmel>{{cite book|url=https://books.google.com/books?id=I3gxuwTE5_MC&pg=PA10|title=Managing roadway snow and ice control operations|author=David A. Kuemmel|page=10|isbn=978-0-309-05666-3|publisher=Transportation Research Board|year=1994|access-date=July 8, 2009}}</ref> The [[Federal Highway Administration]] ''Manual of Practice for an Effective Anti-icing Program'' emphasizes "anti-icing" procedures that prevent the bonding of snow and ice to the road. Key aspects of the practice include: understanding anti-icing in light of the level of service to be achieved on a given roadway, the climatic conditions to be encountered, and the different roles of deicing, anti-icing, and abrasive materials and applications, and employing anti-icing "toolboxes", one for operations, one for decision-making and another for personnel. The elements to the toolboxes are:<ref name=FHWA>
{{cite web
 |url         = https://www.fhwa.dot.gov/reports/mopeap/mop0296a.htm#eapappa2
 |title       = Manual of Practice for an Effective Anti-icing Program: A Guide For Highway Winter Maintenance Personnel
 |last1        = Ketcham
 |first1       = Stephen A.
 |last2       = Minsk
 |first2      = L. David
 |display-authors=2
 |author3=Robert R. Blackburn
 |author4=Edward J. Fleege
 |date        = June 1995
 |website     = [[Federal Highway Administration|Federal Highway Administration (FHWA)]]
 |publisher   = FHWA
 |access-date = December 1, 2016
 |quote       = Highway anti-icing is the snow and ice control practice of preventing the formation or development of bonded snow and ice by timely applications of a chemical freezing-point depressant.
 |url-status=live
 |archive-url  = https://web.archive.org/web/20161201084330/http://www.fhwa.dot.gov/reports/mopeap/mop0296a.htm#eapappa2
 |archive-date = December 1, 2016
 |df          = mdy-all
}}</ref>
* ''Operations'' – Addresses the application of solid and liquid chemicals, using various techniques, including prewetting of chloride-salts. It also addresses plowing capability, including types of snowplows and blades used.
* ''Decision-making'' – Combines weather forecast information with road information to assess the upcoming needs for application of assets and the evaluation of treatment effectiveness with operations underway.
* ''Personnel'' – Addresses training and deployment of staff to effectively execute the anti-icing program, using the appropriate materials, equipment and procedures.
The manual offers matrices that address different types of snow and the rate of snowfall to tailor applications appropriately and efficiently.

[[Snow fence]]s, constructed upwind of roadways control snow drifting by causing windblown, drifting snow to accumulate in a desired place. They are also used on railways. Additionally, farmers and ranchers use snow fences to create drifts in basins for a ready supply of water in the spring.<ref>{{Citation| first1 =R| last1 =Jairell| first2 =R| last2 =Schmidt| title =Snow Management and Windbreaks| contribution =133| series =Range Beef Cow Symposium| year =1999| pages =12| publisher =[[University of Nebraska–Lincoln]]| url =http://www1.foragebeef.ca/$Foragebeef/frgebeef.nsf/all/frg4952/$FILE/snow_mgmt.pdf| url-status=live| archive-url =https://web.archive.org/web/20160507023359/http://www1.foragebeef.ca/$Foragebeef/frgebeef.nsf/all/frg4952/$FILE/snow_mgmt.pdf| archive-date =May 7, 2016| df =mdy-all}}</ref><ref>{{cite journal|url=https://www.sciencedaily.com/releases/2009/01/090129113327.htm|title='SnowMan' Software Helps Keep Snow Drifts Off The Road|date=February 6, 2009|journal=ScienceDaily|access-date=July 12, 2009|url-status=live|archive-url=https://web.archive.org/web/20090416122409/https://www.sciencedaily.com/releases/2009/01/090129113327.htm|archive-date=April 16, 2009|df=mdy-all}}</ref>

====Aviation====
{{See also|Ice protection system}}
[[File:2008 aircraft deicing at gate.jpg|thumb|right|Deicing an aircraft during a snow event]]
In order to keep airports open during winter storms, runways and taxiways require snow removal. Unlike roadways, where chloride chemical treatment is common to prevent snow from bonding to the pavement surface, such chemicals are typically banned from airports because of their strong corrosive effect on aluminum aircraft. Consequently, mechanical brushes are often used to complement the action of snow plows. Given the width of runways on airfields that handle large aircraft, vehicles with large plow blades, an echelon of plow vehicles or [[rotary snowplow]]s are used to clear snow on runways and taxiways. Terminal aprons may require {{convert|6|ha}} or more to be cleared.<ref name=Vinson>
{{Citation
 |first1            = Becker
 |last1             = John C.
 |first2           = David C.
 |last2            = Esch
 |editor-last      = Vinson
 |editor-first     = Ted S.
 |editor2-last     = Rooney
 |editor2-first    = James W.
 |editor3-last     = Haas
 |editor3-first    = Wilbur H.
 |title            = Roads and Airfields in Cold Regions: A State of the Practice Report
 |contribution     = Road and airfield maintenance
 |series           = CERF Reports
 |year             = 1996
 |page             = 252
 |publisher        = ASCE Publications
 |url              = https://books.google.com/books?id=VfO8QuV0q0sC&pg=PA252
 |isbn             = 978-0-7844-7412-9
 }}</ref>

Properly equipped aircraft are able to fly through snowstorms under [[instrument flight rules]]. Prior to takeoff, they require [[deicing fluid]] during snowstorms to prevent accumulation and freezing of snow and other precipitation on wings and fuselages, which may compromise the safety of the aircraft and its occupants.<ref>Transport Canada, Ottawa, ON (2016). [http://www.tc.gc.ca/eng/civilaviation/publications/tp14052-chapter8-312.htm "TP 14052. Guidelines for Aircraft Ground-Icing Operations. Chapter 8. Fluids."] {{webarchive|url=https://web.archive.org/web/20140527220255/http://www.tc.gc.ca/eng/civilaviation/publications/tp14052-chapter8-312.htm |date=May 27, 2014 }} Retrieved May 14, 2016.</ref> In flight, aircraft rely on a variety of mechanisms to avoid rime and other types of icing in clouds,<ref>
{{cite web
 | url = http://www.airspacemag.com/how-things-work/electro-mechanical-deicing-6660440/
 | title = Electro-mechanical deicing
 | last = Wright
 | first = Tim
 | date = March 2004
 | website = Air & Space Magazine
 | publisher = Smithsonian
 | access-date = February 20, 2017
 }}</ref> these include pulsing [[deicing boot|pneumatic boots]], electro-thermal areas that generate heat, and fluid deicers that bleed onto the surface.<ref>{{cite web
 |url         = https://www.aopa.org/-/media/files/aopa/home/pilot-resources/asi/safety-advisors/sa22.pdf?la=en
 |title       = Aircraft Deicing and Anti-icing Equipment
 |last        = Ells
 |first       = Steve
 |date        = 2004
 |website     = Safety Advisor – Weather No. 2
 |publisher   = Aircraft Owners and Pilots Association
 |access-date = December 1, 2016
 |quote       = Anti-icing equipment is turned on before entering icing conditions and is designed to prevent ice from forming. Deicing equipment is designed to remove ice after it begins to accumulate on the airframe.
 |url-status=live
 |archive-url  = https://web.archive.org/web/20161203000432/https://www.aopa.org/-/media/files/aopa/home/pilot-resources/asi/safety-advisors/sa22.pdf?la=en
 |archive-date = December 3, 2016
 |df          = mdy-all
}}</ref>

====Rail====
Railroads have traditionally employed two types of snow plows for clearing track: the [[wedge plow]], which casts snow to both sides, and the [[rotary snowplow]], which is suited for addressing heavy snowfall and casting snow far to one side or the other. Prior to the invention of the rotary snowplow ca. 1865, it required multiple [[locomotive]]s to drive a wedge plow through deep snow. After clearing the track with such plows, a "flanger" is used to clear snow from between the rails that are below the reach of the other types of plows. Where icing may affect the steel-to-steel contact of locomotive wheels on track, abrasives (typically sand) have been used to provide traction on steeper uphills.<ref>
{{cite book
 | last = Bianculli
 | first = Anthony J.
 | title = The American Railroad in the Nineteenth Century – Cars
 | publisher = University of Delaware Press
 | series = Trains and Technology
 | volume = 2
 | date = 2001
 | location = Dover
 | page = 170
 | url = https://books.google.com/books?id=2fh0H0USx-0C&pg=PA170
 | access-date = December 2, 2016
 | isbn = 978-0-87413-730-9 }}</ref>

Railroads employ [[snow shed]]s—structures that cover the track—to prevent the accumulation of heavy snow or avalanches to cover tracks in snowy mountainous areas, such as the [[Alps]] and the [[Rocky Mountains]].<ref>{{cite web
 |url         = http://www.fao.org/docrep/x5376e/x5376e04.htm
 |title       = Avalanche and torrent control in the Spanish Pyrenees
 |last        = FAO
 |first       = Staff
 |website     = National Forests Organization of Spain
 |publisher   = Patrimonio Forestal del Estado
 |access-date = December 1, 2016
 |url-status=live
 |archive-url  = https://web.archive.org/web/20150924140432/http://www.fao.org/docrep/x5376e/x5376e04.htm
 |archive-date = September 24, 2015
 |df          = mdy-all
}}</ref>
<gallery caption="Snowplows for different transportation modes" mode="packed" heights="150px">
File:TowPLow front view2.JPG|Trucks plowing snow on a highway in [[Missouri]]
File:Winter Operations @ Brussels Airport January 2013 (8387468508).jpg|Airport snow-clearing operations include plowing and brushing
File:RhB ABe 8-12 Allegra mit Spurpflug bei Ospizio Bernina.jpg|Swiss low-profile, train-mounted snowplow
</gallery>

====Construction====
Snow can be compacted to form a [[snow road]] and be part of a [[Winter road|winter road route]] for vehicles to access isolated communities or construction projects during the winter.<ref name = Abele>Abele, G., 1990. Snow roads and runways, U.S. Army Cold Regions Research and Engineering Laboratory, Monograph 90-3, Washington, D.C.</ref> Snow can also be used to provide the supporting structure and surface for a runway, as with the [[Phoenix Airfield]] in Antarctica. The snow-compacted runway is designed to withstand approximately 60 wheeled flights of heavy-lift military aircraft a year.<ref name="usap4212">{{cite web| url=http://www.usap.gov/News/contentHandler.cfm?id=4212| title=A New Runway for McMurdo Station is Named| publisher=National Science Foundation| date=7 April 2016| url-status=live| archive-url=https://web.archive.org/web/20160423090553/http://www.usap.gov/News/contentHandler.cfm?id=4212| archive-date=April 23, 2016| df=mdy-all}}</ref>

===Agriculture===
[[File:Indus.A2002274.0610.1km.jpg|thumb|Satellite view of the [[Indus River Basin]], showing snow in the mountain ranges—including the Himalayas—which feed the Indus river and its tributaries, and agricultural areas in eastern [[Pakistan]] and northwestern [[India]] that draw on them for irrigation.]]
Snowfall can be beneficial to agriculture by serving as a [[thermal insulation|thermal insulator]], conserving the heat of the Earth and protecting [[agriculture|crops]] 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, both directly and via runoff through streams and rivers, which supply irrigation canals.<ref name = Snowenclyclopedia/> The following are examples of rivers that rely on meltwater from glaciers or seasonal snowpack as an important part of their flow on which irrigation depends: the [[Ganges]], many of whose tributaries rise in the [[Himalayas]] and which provide much irrigation in northeast [[India]],<ref>{{cite book
 |first1      = C. R.
 |last1       = Krishna Murti
 |others      = Gaṅgā Pariyojanā Nideśālaya; India Environment Research Committee
 |title       = The Ganga, a scientific study
 |date        = 1991
 |publisher   = Northern Book Centre
 |isbn        = 978-8172110215
 |df          = mdy-all
|oclc       = 853267663
 }}</ref> the [[Indus River]], which rises in [[Tibet]]<ref>[[Alice Albinia|Albinia, Alice]]. (2008) ''Empires of the Indus: The Story of a River''. First American Edition (20101) W. W. Norton & Company, New York. {{ISBN|978-0-393-33860-7}}.</ref> and provides irrigation water to [[Pakistan]] from rapidly retreating Tibetan glaciers,<ref>{{cite web |url=https://www.google.com/hostednews/afp/article/ALeqM5g1eE4Xw3njaW1MKpJRYOch4hOdLQ |title=Global warming benefits to Tibet: Chinese official. Reported 18 August 2009 |date=August 17, 2009 |access-date=December 4, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20100123192540/https://www.google.com/hostednews/afp/article/ALeqM5g1eE4Xw3njaW1MKpJRYOch4hOdLQ |archive-date=January 23, 2010 |df=mdy-all }}</ref> and the [[Colorado River]], which receives much of its water from seasonal snowpack in the [[Rocky Mountains]]<ref name="USGSrivers">{{cite web|url=http://pubs.usgs.gov/of/1987/ofr87-242/|author=Kammerer, J.C.|title=Largest Rivers in the United States|publisher=U.S. Geological Survey|date=May 1990|access-date=July 2, 2010|url-status=live|archive-url=https://web.archive.org/web/20170129040848/https://pubs.usgs.gov/of/1987/ofr87-242/|archive-date=January 29, 2017|df=mdy-all}}</ref> and provides irrigation water to some {{convert|4|e6acre|e6ha|abbr=off}}.<ref>{{cite web|url=http://www.usbr.gov/newsroom/newsrelease/detail.cfm?RecordID=38043|title=Salazar Awards $20.1 Million to Four Western Colorado Irrigation Districts to Improve Irrigation Systems, Reduce Salinity in Colorado River|publisher=U.S. Bureau of Reclamation|date=October 21, 2011|access-date=March 17, 2012|url-status=dead|archive-url=https://web.archive.org/web/20111030103029/http://www.usbr.gov/newsroom/newsrelease/detail.cfm?RecordID=38043|archive-date=October 30, 2011|df=mdy-all}}</ref>

===Structures===
[[File:Snow in Grindelwald.jpg|thumb|right|Extreme snow accumulation on building roofs]]
Snow is an important consideration for loads on structures. To address these, European countries employ ''Eurocode 1: Actions on structures - Part 1-3: General actions - Snow loads''.<ref name=Eurocode1>
{{Citation
 | author = Joint European Commission
 | title = General actions - Snow loads
 | journal = Eurocode 1
 | volume = EN 1991-1-3:2003
 | issue = Actions on structures - Part 1–3
 | year = 2003
 | url = http://eurocodes.jrc.ec.europa.eu/showpage.php?id=131 }}</ref> In North America, ASCE ''Minimum Design Loads for Buildings and Other Structures'' gives guidance on snow loads.<ref name=ASCE7>
{{Citation
 |author      = Committee on Minimum Design Loads for Buildings
 |title       = Minimum Design Loads for Buildings and Other Structures
 |issue       = ASCE 7–10
 |pages       = 636
 |year        = 2013
 |url         = https://law.resource.org/pub/us/cfr/ibr/003/asce.7.2002.pdf
 |publisher   = American Society of Civil Engineers
 |access-date = December 2, 2016
 |isbn        = 9780784413227
 |url-status=live
 |archive-url  = https://web.archive.org/web/20161011024914/https://law.resource.org/pub/us/cfr/ibr/003/asce.7.2002.pdf
 |archive-date = October 11, 2016
 |df          = mdy-all
}}</ref> Both standards employ methods that translate maximum expected ground snow loads onto design loads for roofs.

====Roofs====
[[File:Ice dam and roof leakage.jpg|thumb|right|Icings resulting from meltwater at the bottom of the snow pack on the roof, flowing and refreezing at the eave as icicles and from leaking into the wall via an ice dam.]]
Snow loads and icings are two principal issues for roofs. Snow loads are related to the climate in which a structure is sited. Icings are usually a result of the building or structure generating heat that melts the snow that is on it.

''Snow loads'' – The ''Minimum Design Loads for Buildings and Other Structures'' gives guidance on how to translate the following factors into roof snow loads:<ref name = ASCE7/>
* Ground snow loads
* Exposure of the roof
* Thermal properties of the roof
* Shape of the roof
* Drifting
* Importance of the building
It gives tables for ground snow loads by region and a methodology for computing ground snow loads that may vary with elevation from nearby, measured values. The ''Eurocode 1'' uses similar methodologies, starting with ground snow loads that are tabulated for portions of Europe.<ref name=Eurocode1/>

''Icings'' – Roofs must also be designed to avoid [[Ice dam (roof)|ice dams]], which result from meltwater running under the snow on the roof and freezing at the eave. Ice dams on roofs form when accumulated snow on a sloping roof melts and flows down the roof, under the insulating blanket of snow, until it reaches below freezing temperature air, typically at the [[eaves]]. When the meltwater reaches the freezing air, ice accumulates, forming a dam, and snow that melts later cannot drain properly through the dam.<ref name="Paul" >Paul Fisette, "Preventing Ice Dams", ''Roofing, flashing & waterproofing''. Newtown, CT: Taunton Press, 2005. 54.</ref> Ice dams may result in [[Water damage|damaged]] building materials or in damage or injury when the ice dam falls off or from attempts to remove ice dams. The melting results from heat passing through the roof under the highly insulating layer of snow.<ref>{{citation| url=http://www.state.mn.us/portal/mn/jsp/content.do?test=y&id=-536881350&subchannel=-536881511&sc2=null&sc3=null&contentid=536884951&contenttype=EDITORIAL&programid=536886479&agency=Commerce|title=Ice Dams|publisher=Minnesota Department of Commerce|archive-url=https://web.archive.org/web/20070824154322/http://www.state.mn.us/portal/mn/jsp/content.do?test=y&id=-536881350&subchannel=-536881511&sc2=null&sc3=null&contentid=536884951&contenttype=EDITORIAL&programid=536886479&agency=Commerce| archive-date=August 24, 2007}}</ref><ref name="Hansen" >
{{Citation
 | first1 = I.
 | last1 = MacKinley
 | first2 = R.
 | last2 = Flood
 | first3 = A.
 | last3 = Heidrich
 | editor-last = Hjorth-Hansen
 | editor-first = E.
 | editor2-last = Holand
 | editor2-first = I.
 | editor3-last = Loset
 | editor3-first = S.
 | editor4-last = Norem
 | editor4-first = H.
 | contribution = Roof design in regions of snow and cold
 | isbn = 9789058091482
 | title = Snow Engineering 2000: Recent Advances and Developments
 | year = 2000
 | pages = 470
 | place = Rotterdam
 | publisher = CRC Press
 | url = https://books.google.com/books?id=EjGsPSoYHOIC
}}</ref>

====Utility lines====
In areas with trees, utility distribution lines on poles are less susceptible to snow loads than they are subject to damage from trees falling on them, felled by heavy, wet snow.<ref>
{{cite web
 |url         = https://www.progress-energy.com/carolinas/home/safety-information/storm-safety-tips/outages.page?
 |title       = Storms & Outages
 |last        = Technical staff
 |date        = 2015
 |publisher   = Duke Energy
 |access-date = December 6, 2016
 |quote       = Both snow and ice cause power outages primarily by weighing down tree limbs and power lines, causing them to break
 |url-status=dead
 |archive-url  = https://web.archive.org/web/20161220104742/https://www.progress-energy.com/carolinas/home/safety-information/storm-safety-tips/outages.page
 |archive-date = December 20, 2016
 |df          = mdy-all
}}</ref> Elsewhere, snow can accrete on power lines as "sleeves" of rime ice. Engineers design for such loads, which are measured in kg/m (lb/ft) and power companies have forecasting systems that anticipate types of weather that may cause such accretions. Rime ice may be removed manually or by creating a sufficient short circuit in the affected segment of power lines to melt the accretions.<ref>{{Citation
 | last = Farzaneh
 | first = Masoud
 | title = Atmospheric Icing of Power Networks
 | publisher = Springer Science & Business Media
 | year = 2008
 | page = 141
 | url = https://books.google.com/books?id=Ufg-AAAAQBAJ&pg=PA141
 | isbn = 9781402085314 }}</ref><ref>{{Citation
 |last1            = Bonelli
 |first1           = P.
 |last2           = Lacavalla
 |first2          = M.
 |display-authors = etal <!--P. Marcacci, G. Mariani, and G. Stella-->
 |title           = Wet snow hazard for power lines: a forecast and alert system applied in Italy
 |journal         = Natural Hazards and Earth System Sciences
 |volume          = 11
 |issue           = 9
 |year            = 2011
 |pages           = 2419–2431
 |doi             = 10.5194/nhess-11-2419-2011
 |bibcode         = 2011NHESS..11.2419B
 |s2cid = 15569449
 |df              = mdy-all
|doi-access= free
 }}</ref>

===Sports and recreation===
[[File:Ski Famille - Family Ski Holidays.jpg|thumb|Alpine skiing]]
{{Main|Winter sport}}
Snow figures into many winter sports and forms of recreation, including [[skiing]] and [[sledding]]. Common examples include [[cross-country skiing]], [[Alpine skiing]], [[snowboarding]], [[snowshoe]]ing, and [[Snowmobile|snowmobiling]]. The design of the equipment used, e.g. skis and snowboards, typically relies on the bearing strength of snow and contends with the [[coefficient of friction]] bearing on snow.

Skiing is by far the largest form of winter recreation. As of 1994, of the estimated 65–75 million skiers worldwide, there were approximately 55 million who engaged in [[Alpine skiing]], the rest engaged in [[cross-country skiing]]. Approximately 30 million skiers (of all kinds) were in Europe, 15 million in the US, and 14 million in Japan. As of 1996, there were reportedly 4,500 ski areas, operating 26,000 ski lifts and enjoying 390 million skier visits per year. The preponderant region for downhill skiing was Europe, followed by Japan and the US.<ref>
{{cite book
 | last = Hudson
 | first = Simon
 | title = Snow Business: A Study of the International Ski Industry
 | publisher = Cengage Learning EMEA
 | series = Tourism (Cassell)
 | date = 2000
 | pages = 180
 | url = https://books.google.com/books?id=tGRLt8tG-kMC&pg=PA27
 | isbn = 9780304704712}}</ref>

Increasingly, ski resorts are relying on [[snowmaking]], the production of snow by forcing water and pressurized air through a [[Snowmaking#Snowmaking guns|snow gun]] on ski slopes.<ref>{{US patent reference|number=2676471|inventor=W. M. Pierce Jr.|title=Method for Making and Distributing Snow|issue-date=December 14, 1950}}</ref> Snowmaking is mainly used to supplement natural snow at [[ski resort]]s.<ref>[http://news.bbc.co.uk/onthisday/hi/dates/stories/march/25/newsid_2786000/2786871.stm On This Day: March 25] {{webarchive|url=https://web.archive.org/web/20110412010130/http://news.bbc.co.uk/onthisday/hi/dates/stories/march/25/newsid_2786000/2786871.stm |date=April 12, 2011 }}, [[BBC News]], accessed December 20, 2006. "The first artificial snow was made two years later, in 1952, at Grossinger's resort in New York, USA. "</ref> This allows them to improve the reliability of their snow cover and to extend their ski seasons from late autumn to early spring. The production of snow requires low temperatures. The threshold temperature for snowmaking increases as humidity decreases. [[Wet-bulb temperature]] is used as a metric since it takes air temperature and relative humidity into account. Snowmaking is a relatively expensive process in its energy consumption, thereby limiting its use.<ref>{{citation|url=http://bachler.cms1.ch/Portals/41/docs/energy_usage_for_snowmaking.pdf|title=Energy usage for snowmaking|author=Jörgen Rogstam|author2=Mattias Dahlberg|name-list-style=amp|date=April 1, 2011|url-status=live|archive-url=https://web.archive.org/web/20140201200900/http://bachler.cms1.ch/Portals/41/docs/energy_usage_for_snowmaking.pdf|archive-date=February 1, 2014|df=mdy-all}}</ref>

[[Ski wax]] enhances the ability of a ski (or other runner) to slide over snow by reducing its coefficient of friction, which depends on both the properties of the snow and the ski to result in an optimum amount of lubrication from melting the snow by friction with the ski—too little and the ski interacts with solid snow crystals, too much and capillary attraction of meltwater retards the ski. Before a ski can slide, it must overcome the maximum value static friction. Kinetic (or dynamic) friction occurs when the ski is moving over the snow.<ref name="Bhavikatti">{{cite book
| url = https://books.google.com/books?id=4wkLl4NvmWAC&pg=PA112
| title = Engineering Mechanics
| last = Bhavikatti
| first = S. S.
|author2=K. G. Rajashekarappa
| page = 112
| access-date = October 21, 2007
| publisher = New Age International
| isbn = 978-81-224-0617-7
| year = 1994}}</ref>

===Warfare===
{{main|Cold-weather warfare}}
{{see also|Ski warfare}}
Snow affects warfare conducted in winter, alpine environments or at high latitudes. The main factors are ''impaired visibility'' for acquiring targets during falling snow, ''enhanced visibility'' of targets against snowy backgrounds for targeting, and mobility for both [[Mechanized infantry|mechanized]] and [[infantry]] troops. Snowfall can severely inhibit the [[Military logistics|logistics of supplying troops]], as well. Snow can also provide cover and fortification against small-arms fire.<ref name=chew>{{cite journal
 |last        = Chew
 |first       = Allen F.
 |title       = Fighting the Russians in Winter: Three Case Studies
 |journal     = Leavenworth Papers
 |issue       = 5
 |place       = Fort Leavenworth, Kansas
 |date        = December 1981
 |url         = http://www.cgsc.edu/carl/download/csipubs/chew.pdf
 |issn        = 0195-3451
 |access-date = December 10, 2016
 |url-status=dead
 |archive-url  = https://web.archive.org/web/20111013030919/http://cgsc.edu/carl/download/csipubs/chew.pdf
 |archive-date = October 13, 2011
 |df          = mdy-all
}}</ref> Noted [[winter warfare]] campaigns where snow and other factors affected the operations include:
* The [[French invasion of Russia]], where poor traction conditions for ill-shod horses made it difficult for supply wagons to keep up with troops.<ref>{{cite news |url=https://www.bbc.co.uk/news/magazine-16929522 |title=Napoleon's failure: For the want of a winter horseshoe |work=BBC News magazine |author=Professor Saul David |date=February 9, 2012 |access-date=February 9, 2012 |url-status=live |archive-url=https://web.archive.org/web/20120209074411/http://www.bbc.co.uk/news/magazine-16929522 |archive-date=February 9, 2012 |df=mdy-all }}</ref> That campaign was also strongly affected by cold, whereby the retreating army reached [[Neman River]] in December 1812 with only 10,000 of the 420,000 that had set out to invade [[Russia]] in June of the same year.<ref name="The Wordsworth Pocket Encyclopedia p. 17">The Wordsworth Pocket Encyclopedia, p. 17, Hertfordshire 1993.</ref>
* The [[Winter War]], an attempt by the [[Soviet Union]] to take territory in [[Finland]] in late 1939 demonstrated superior winter tactics of the [[Finnish Army]], regarding over-snow mobility, [[camouflage]], and use of the terrain.<ref name="Clemmesen">{{cite book |editor1-last=Clemmesen |editor1-first=Michael H. |editor2-last=Faulkner |editor2-first=Marcus |title=Northern European Overture to War, 1939–1941: From Memel to Barbarossa| year=2013 |publisher=Brill |page=76 |isbn=978-90-04-24908-0}}</ref>
* The [[Battle of the Bulge]], a German counteroffensive during [[World War II]], starting December 16, 1944, was marked by heavy snowstorms that hampered allied air support for ground troops, but also impaired German attempts to supply their front lines.<ref>{{citation |last=Parker |first=Danny S. |title=Battle of the Bulge: Hitler's Ardennes Offensive, 1944–1945 |publisher=Combined Books |year=1991 |isbn=978-0-938289-04-3}}</ref> On the Eastern Front with the Nazi invasion of Russia in 1941, [[Operation Barbarossa]], both Russian and German soldiers had to endure terrible conditions during the [[Russian winter]]. While use of [[ski infantry]] was common in the Red Army, Germany formed only [[1st Ski Division (Germany)|one division]] for movement on skis.<ref name="Clemmesen"/>
* The [[Korean War]] which lasted from June 25, 1950, until an armistice on July 27, 1953, began when [[North Korea]] invaded [[South Korea]]. Much of the fighting occurred during winter conditions, involving snow,<ref>{{cite book
| last = Halberstam
| first = David
| author-link = David Halberstam
| year = 2007
| title = The Coldest Winter: America and the Korean War
| publisher = Hyperion
| location = New York
| isbn = 978-1-4013-0052-4
| title-link = The Coldest Winter: America and the Korean War
}}</ref> notably during the [[Battle of Chosin Reservoir]], which was a stark example of cold affecting military operations, especially vehicles and weapons.<ref>
{{cite book
 | last = Tilstra
 | first = Russell C.
 | title = The Battle Rifle: Development and Use Since World War II
 | publisher = McFarland
 | date = 2014
 | page = 28
 | url = https://books.google.com/books?id=_a0zAwAAQBAJ&pg=PA28
 | isbn = 978-1-4766-1564-6 }}</ref>
<gallery caption="Military operations in snow" mode="packed" heights="150px">
File:Night Bivouac of Great Army.jpg|Bivouac of [[Napoleon]]'s [[Grande Armée]], during the winter retreat from [[Moscow]]
File:Finn ski troops.jpg|Finnish ski troops during the invasion of [[Finland]] by the [[Soviet Union]]
File:Army vehicles on a road in Belgium.jpg|Army vehicles coping with snow during the [[Battle of the Bulge]] of [[World War II]]
File:Cold Response DV dag.jpg|Norwegian military preparations during the 2009 [[Cold Response]] exercise
File:Navy Seals Winter warfare at Mammoth Mountain, California, in December 2014.jpg|[[United States Navy SEALs]] training for winter warfare at [[Mammoth Mountain]], [[California]]
</gallery>