Мраз — разлика између измена
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Ред 1:
{{Short description|Облагање или таложење леда}}{{рут}}
[[Датотека:Frost on black pipes.jpg|мини|десно|250px|Мраз на кабловима.]]
'''Мраз''' је појавни облик воде када се она смрзне у виду [[кристал]]а [[лед]]а који приањају уз [[Грана (ботаника)|гранчице]], влати [[трава|траве]] или рецимо [[прозор]]е. Мраз је бео јер кристали леда садрже [[ваздух]]. '''[[Иње]]''' и '''[[слана]]''' су у [[природа|природи]] појаве сличне овој.<ref>Група аутора, 1976. Популарна енциклопедија. БИГЗ: Београд.</ref><ref>Стојановић, В. Публикација: Вода - извор живота, моћ, изазов. Март 2005. НИП „Дечја кућа“ д. о. о. Горњи Милановац. {{ISBN|978-86-85371-02-8}}.</ref>▼
[[Датотека:Saint-Amant 16 Gelée blanche 2008.jpg|thumb|250px|A patch of grass showing crystalline frost in the below-freezing shade (blue, lower right); frost in the warming but still below freezing strip most recently exposed to sunlight (white, center); and a frost-free region: here, the previous frost has melted from a more prolonged exposure to sunlight (green, upper left.)]]
▲'''Мраз''' је појавни облик воде када се она смрзне у виду [[кристал]]а [[лед]]а који приањају уз [[Грана (ботаника)|гранчице]], влати [[трава|траве]] или рецимо [[прозор]]е.<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/frost|title=Frost – Definition of frost by Merriam-Webster|work=merriam-webster.com|url-status=live|archive-url=https://web.archive.org/web/20150511025533/http://www.merriam-webster.com/dictionary/frost|archive-date=2015-05-11}}</ref><ref>{{cite web |url=http://www.weatherquestions.com/What_causes_frost.htm |title=What causes frost? |access-date=2007-12-05 |url-status=live |archive-url=https://web.archive.org/web/20071210230539/http://www.weatherquestions.com/What_causes_frost.htm |archive-date=2007-12-10 }}</ref> Мраз је бео јер кристали леда садрже [[ваздух]]. '''[[Иње]]''' и '''[[слана]]''' су у [[природа|природи]] појаве сличне овој.<ref>Група аутора, 1976. Популарна енциклопедија. БИГЗ: Београд.</ref><ref>Стојановић, В. Публикација: Вода - извор живота, моћ, изазов. Март 2005. НИП „Дечја кућа“ д. о. о. Горњи Милановац. {{ISBN|978-86-85371-02-8}}.</ref> In [[temperate climate]]s, it most commonly appears on surfaces near the ground as fragile white [[crystals]]; in cold climates, it occurs in a greater variety of forms.<ref name="Oliver2005">{{cite book|author=John E. Oliver|title=The Encyclopedia of World Climatology|url=https://books.google.com/books?id=-mwbAsxpRr0C&pg=PA382|date=1 January 2005|publisher=[[Springer Science & Business Media]]|isbn=978-1-4020-3264-6|pages=382–|url-status=live|archive-url=https://web.archive.org/web/20160508153444/https://books.google.com/books?id=-mwbAsxpRr0C&pg=PA382|archive-date=8 May 2016}}</ref> The propagation of crystal formation occurs by the process of [[nucleation]].
== Типови ==
===Hoar frost===
[[File:Frostweb.jpg|thumb|left|250px|A [[spider web]] covered in air hoar frost]]
[[File:HoarFrost.jpg|thumb|250px|Hoar frost on the snow]]
[[File:LightLTSEM.jpg|thumb|десно|250px|Depth hoar, [[micrograph|imaged]] with [[optical microscope|optical]] (left) and [[scanning electron microscope|scanning electron]] (right) [[microscopy]]]]
'''Hoar frost''', also '''hoarfrost''', '''radiation frost''', or '''pruina''', refers to white ice crystals deposited on the ground or loosely attached to exposed objects, such as wires or leaves.<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/hoar%20frost|title=Hoarfrost – Definition of hoarfrost by Merriam-Webster|work=merriam-webster.com|url-status=live|archive-url=https://web.archive.org/web/20150219065328/http://www.merriam-webster.com/dictionary/hoar%20frost|archive-date=2015-02-19}}</ref> They form on cold, clear nights when conditions are such that [[radiative cooling#Nocturnal surface cooling|heat radiates]] out to the open air faster than it can be replaced from nearby sources, such as wind or warm objects. Under suitable circumstances, objects cool to below the [[dew point#Frost point|frost point]]<ref name="RohliRohli2013">{{cite book|author1=Louisiana State University Baton Rouge Robert V. Rohli|author2=Robert V. Rohli|author3=Anthony J. Vega|title=Climatology|url=https://books.google.com/books?id=AxWEAgAAQBAJ&pg=PA381|date=13 December 2013|publisher=[[Jones & Bartlett Publishers]]|isbn=978-1-284-05427-9|pages=381–|url-status=live|archive-url=https://web.archive.org/web/20160519122238/https://books.google.com/books?id=AxWEAgAAQBAJ&pg=PA381|archive-date=19 May 2016}}</ref> of the surrounding air, well below the freezing point of water. Such freezing may be promoted by effects such as '''flood frost''' or '''frost pocket'''.<ref>{{cite web|url=http://www.weatheronline.co.uk/reports/wxfacts/Frost-hollow.htm|title=Weather Facts: Frost hollow – Weather UK – weatheronline.co.uk|work=weatheronline.co.uk|url-status=live|archive-url=https://web.archive.org/web/20130212022607/http://www.weatheronline.co.uk/reports/wxfacts/Frost-hollow.htm|archive-date=2013-02-12}}</ref> These occur when ground-level radiation losses cool air until it flows downhill and accumulates in pockets of very cold air in valleys and hollows. Hoar frost may freeze in such low-lying cold air even when the air temperature a few feet above ground is well above freezing.
When surface hoar covers sloping snowbanks, the layer of frost crystals may create an [[avalanche]] risk; when heavy layers of new snow cover the frosty surface, furry crystals standing out from the old snow hold off the falling flakes, forming a layer of voids that prevents the new snow layers from bonding strongly to the old snow beneath. Ideal conditions for hoarfrost to form on snow are cold, clear nights, with very light, cold air currents conveying humidity at the right rate for growth of frost crystals. Wind that is too strong or warm destroys the furry crystals, and thereby may permit a stronger bond between the old and new snow layers. However, if the winds are strong enough and cold enough to lay the crystals flat and dry, carpeting the snow with cold, loose crystals without removing or destroying them or letting them warm up and become sticky, then the frost interface between the snow layers may still present an avalanche danger, because the texture of the frost crystals differs from the snow texture, and the dry crystals will not stick to fresh snow. Such conditions still prevent a strong bond between the snow layers.<ref name="McClungSchaerer2006">{{cite book|author1=David McClung|author2=Peter A. Schaerer|title=The Avalanche Handbook|url=https://books.google.com/books?id=0Bpscs7Gqb8C&pg=PA72|year=2006|publisher=[[The Mountaineers Books]]|isbn=978-0-89886-809-8|pages=72–|url-status=live|archive-url=https://web.archive.org/web/20160506012123/https://books.google.com/books?id=0Bpscs7Gqb8C&pg=PA72|archive-date=2016-05-06}}</ref>
== Настанак ==
Линија 7 ⟶ 21:
== Последице ==
[[Датотека:WindowFrost121609.jpg|мини|left|250px|Мраз на прозору]]
С обзиром да лед заузима већу [[запремина|запремину]] од воде, а биљке, као и сва жива бића, садрже воду у својим [[Ћелија (биологија)|ћелијама]], ширење леда ће проузроковати цепање и разарање ћелија и одумирање ткива. Такође, мржњење воде у ћелијама ће спречити нормално одвијање [[физиологија|физиолошких]] процеса. Дакле, ова појава је негативна за биљке, а може бити веома штетна и за [[човек]]а. Изложеност мразу може да проузрукује [[промрзлина|промрзлине]], посебно изложених делова као што су [[нос]] и [[прст]]и. Промрзлине вишег степена могу спречити [[крв]] да нормално циркулише, што доводи до одумирања [[Ткиво (биологија)|ткива]] у појединим деловима, а у тежим случајевима и до [[смрт]]и.<ref name="оксфорд"/>
Линија 14 ⟶ 28:
== Пољопривреда ==
Како би се спречила опасност од мраза, обрадиво земљиште се залива што доводи до стварања танке [[магла|измаглице]] изнад површине [[тло|земљишта]]. Ова измаглица спречава нагло хлађење земљишта и самим тим, појаву мраза.<ref name="оксфорд"/>
== Утицај на биљке ==
===Damage===
[[File:Feuilles-avec-glace-leaves-with-ice-1.jpg|лево|250px|thumb|Frost on the grass of a public park in November]]
[[File:Geography of Ohio - DPLA - aaba7b3295ff6973b6fd1e23e33cde14 (page 31) (cropped).jpg|thumb|right|250px|Map of average first killing frost in Ohio from "Geography of Ohio," 1923]]
Many plants can be damaged or killed by freezing temperatures or frost. This varies with the type of plant, the tissue exposed, and how low temperatures get; a "light frost" of {{convert|-2|to|0|C|F}} damages fewer types of plants than a "hard frost" below {{convert|-2|C|F}}.<ref name="BI_Frost">{{cite web |url=http://www.botanicalinterests.com/articles/view/26/Frost-Tolerance-of-Vegetables |title=Frost Tolerance of Vegetables |publisher=Botanical Interests |access-date=Nov 12, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131113010216/http://www.botanicalinterests.com/articles/view/26/Frost-Tolerance-of-Vegetables |archive-date=2013-11-13 }}</ref>
Plants likely to be damaged even by a light frost include vines—such as beans, grapes, squashes, melons—along with [[nightshade]]s such as tomatoes, eggplants, and peppers. Plants that may tolerate (or even benefit from) frosts include:<ref>{{cite web |url=http://www.grow-it-organically.com/fall-vegetables.html |title=Fall vegetables vs. Summer vegetables |url-status=live |archive-url=https://web.archive.org/web/20131113011159/http://www.grow-it-organically.com/fall-vegetables.html |archive-date=2013-11-13 }}</ref>
*root vegetables (e.g. beets, carrots, parsnips, onions)
*leafy greens (e.g. lettuces, spinach, chard, cucumber<ref name="JHR_2-2013">{{Citation|url=http://www.degruyter.com/view/j/johr.2013.21.issue-2/johr-2013-0031/johr-2013-0031.xml?format=INT|last=Klosinska|first=Urszula|date=27 February 2014|publisher=de Gruyter|access-date=2014-02-28|title=Low temperature seed germination of cucumber: genetic basis of the tolerance trait|journal=Journal of Horticultural Research|volume=21|issue=2|pages=125–130|display-authors=etal|url-status=live|archive-url=https://web.archive.org/web/20140611011158/http://www.degruyter.com/view/j/johr.2013.21.issue-2/johr-2013-0031/johr-2013-0031.xml?format=INT|archive-date=11 June 2014|doi=10.2478/johr-2013-0031|doi-access=free}}</ref>)
*[[cruciferous vegetables]] (e.g. cabbages, cauliflower, bok choy, broccoli, Brussels sprouts, radishes, kale, collard, mustard, turnips, rutabagas)
Certain [[bacterium|bacteria]], notably ''[[Pseudomonas syringae]]'', are particularly effective at triggering frost formation, raising the nucleation temperature to about {{convert|-2|C|F}}.<ref>{{cite journal |vauthors=Maki LR, Galyan EL, Chang-Chien MM, Caldwell DR |title=Ice Nucleation Induced by Pseudomonas syringae |journal=Applied Microbiology |volume=28 |issue=3 |year=1974 |pages=456–459 |pmid=4371331 |pmc=186742 |doi=10.1128/aem.28.3.456-459.1974}}</ref> Bacteria lacking ice [[nucleation]]-active proteins ([[ice-minus bacteria]]) result in greatly reduced frost damage.<ref>{{cite journal
|last= Lindow |first= Stephen E. |author-link= Steven E. Lindow |author2=Deane C. Arny |author3=Christen D. Upper |title= Bacterial Ice Nucleation: A Factor in Frost Injury to Plants
|journal= Plant Physiology
|volume= 70
|issue= 4
|pages= 1084–1089
|date= October 1982
|pmid= 16662618
|doi= 10.1104/pp.70.4.1084
|pmc= 1065830}}</ref>
===Protection methods===
[[File:Winterschutz.jpg|thumb|лево|250px|[[Roses]] with protection against frost - [[Volksgarten, Vienna]]]]
[[File:CuritibaFrostGeada.jpg|thumb|right|250px|[[Curitiba]] ([[Southern Brazil]]) is the coldest of [[Brazil]]'s [[state capital]]s; the [[greenhouse]] of the [[Botanical Garden of Curitiba]] protects sensitive plants.]]
Typical measures to prevent frost or reduce its severity include one or more of:
*deploying powerful blowers to simulate wind, thereby preventing the formation of accumulations of cold air. There are variations on this theme. One variety is the wind machine, an engine-driven propeller mounted on a vertical pole that blows air almost horizontally. Wind machines were introduced as a method for frost protection in California during the 1920s, but they were not widely accepted until the 1940s and 1950s. Now, they are commonly used in many parts of the world.<ref>wind machine references: http://www.fao.org/3/y7223e/y7223e0d.htm ; https://extension.psu.edu/orchard-frost-protection-with-wind-machines ; http://www.omafra.gov.on.ca/english/engineer/facts/10-045.htm ;</ref> Another is the [[selective inverted sink]],<ref>[http://www.rolexawards.com/laureates/laureate-20-guarga.html Selective Inverted Sink] {{webarchive|url=https://web.archive.org/web/20060318212517/http://www.rolexawards.com/laureates/laureate-20-guarga.html |date=2006-03-18}} Rolex Awards site (won award in ''Technology and Innovation'' category) 1998.</ref> a device which prevents frost by drawing cold air from the ground and blowing it up through a chimney. It was originally developed to prevent frost damage to [[citrus]] fruits in [[Uruguay]]. In New Zealand, [[helicopter]]s are used in similar fashion, especially in the [[vineyard]] regions such as [[Marlborough Region|Marlborough]]. By dragging down warmer air from the [[Inversion (meteorology)|inversion layers]], and preventing the ponding of colder air on the ground, the low-flying helicopters prevent damage to the fruit buds. As the operations are conducted at night, and have in the past involved up to 130 aircraft per night in one region, safety rules are strict.<ref>''Helicopters Fight Frost'' – ''Vector'', [[Civil Aviation Authority of New Zealand]], September/ October 2008, Page 8-9</ref> Although not a dedicated method, [[wind turbine]]s have similar (small) effect of vertically mixing air layers of different temperature.<ref name="Nature-2010.12.23">[http://www.nature.com/nature/journal/v468/n7327/full/4681001a.html Turbines and turbulence] {{webarchive|url=https://web.archive.org/web/20111201212633/http://www.nature.com/nature/journal/v468/n7327/full/4681001a.html |date=2011-12-01}}, ''[[Nature (journal)]]'', 468, 1001, 23 December 2010, DOI:10.1038/4681001a, published online 22 December 2010.</ref><ref name="Roy+Traiteur">Somnath Baidya Roy and Justin J. Traiteur. [http://www.pnas.org/content/early/2010/10/12/1000493107.abstract Impacts of wind farms on surface air temperatures], Proceedings of the National Academy of Sciences, Vol. 107, No. 42, October 19, 2010, p. 17,899.</ref><ref name="ScienceDaily-2005">[https://www.sciencedaily.com/videos/2005/1012-wind_farms_impacting_weather.htm Wind farms impacting weather] {{webarchive|url=https://web.archive.org/web/20100906101845/https://www.sciencedaily.com/videos/2005/1012-wind_farms_impacting_weather.htm |date=2010-09-06}}, Science Daily.</ref>
*For high-value crops, farmers may [[tree wrap|wrap trees]] and cover crops.
*Heating to slow the drop in temperature is not practical except for high-value crops grown over small areas.
*Production of smoke to reduce cooling by radiation
*Spraying crops with a layer of water releases latent heat, preventing harmful freezing of the tissues of the plants that it coats.
Such measures need to be applied with discretion, because they may do more harm than good; for example, spraying crops with water can cause damage if the plants become overburdened with ice. An effective, '''low cost''' method for small crop farms and plant nurseries, exploits the [[enthalpy of fusion|latent heat of freezing]]. A pulsed irrigation timer<ref name=Nurseries/> delivers water through existing overhead sprinklers at a low volumes to combat frosts down to {{convert|-5|C|F}}.<ref name=Nurseries>{{cite web|title=A practical method of frost protection|url=http://plantsale.com.au/Articles/FrostProtection|access-date=31 October 2011|url-status=live|archive-url=https://web.archive.org/web/20120320075831/http://www.plantsale.com.au/Articles/FrostProtection/|archive-date=20 March 2012}}</ref><ref name=SmallCrops>{{cite web|last=Selders|first=Arthur W.|title=Frost protection with sprinkler irrigation|url=http://www.wvu.edu/~agexten/hortcult/fruits/om101.pdf|publisher=West Virginia university|access-date=31 October 2011|url-status=dead|archive-url=https://web.archive.org/web/20111114032130/http://www.wvu.edu/~agexten/hortcult/fruits/om101.pdf|archive-date=14 November 2011}}</ref> If the water freezes, it gives off its latent heat, preventing the temperature of the foliage from falling much below zero.<ref name=SmallCrops/>
== Занимљивост ==
Линија 30 ⟶ 78:
* [https://web.archive.org/web/20070810172555/http://amsglossary.allenpress.com/glossary/search?id=hoarfrost1 American Meteorological Society, ''Glossary of Meteorology'' - Hoarfrost]
* [http://www.islandnet.com/~see/weather/whys/frost.htm The Weather Doctor - Weather Whys - Frost]
* [https://www.bbc.com/weather/features/41763562 How much do you know about frost?] – ''BBC''
* [http://glossary.ametsoc.org/wiki/Frost American Meteorological Society, ''Glossary of Meteorology'' – Hoarfrost]
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