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Yourwebbrowser(Safari7)isoutofdate.Formoresecurity,comfortand thebestexperienceonthissite: Updateyourbrowser Ignore FROST Forthecompleteencyclopedicentrywithmediaresources,visit: http://www.nationalgeographic.org/encyclopedia/frost/ Frostiswatervapor,orwateringasform,thatbecomessolid.Frostusually formsonobjectslikecars,windows,andplantsthatareoutsideinairthatis saturated,orfilled,withmoisture.Areasthathavealotoffogoftenhaveheavy frosts. Frostformswhenanoutsidesurfacecoolspastthedewpoint.Thedewpointis thepointwheretheairgetssocold,thewatervaporintheatmosphereturns intoliquid.Thisliquidfreezes.Ifitgetscoldenough,littlebitsofice,orfrost, form.Theiceisarrangedintheformoficecrystals. Frostismostcommoninlow-lyingareas.Warmairrises,andcoolairsinks— coolairisdenserthanwarmair.Thatmeansthereareusuallymorewater moleculesincoolairthaninwarmair.Ascoolaircollectsinvalleys,frostforms. Frostusuallyformsatnight,whentheairtemperatureiscooler.Oncethesun risesandwarmstheairaroundthefrostedobject,frostmeltsquickly. TypesofFrost Therearedifferenttypesoffrost.Themostcommonareradiationfrost(also calledhoarfrost),advectionfrost,windowfrost,andrime. Radiationfrostisfrostintheformoftinyicecrystalsthatusuallyshowsupon thegroundorexposedobjectsoutside.Hoarfrostalsoformsinrefrigeratorsand freezers. 1of6 Advectionfrostisacollectionofsmallicespikes.Advectionfrostformswhena coldwindblowsoverthebranchesoftrees,poles,andothersurfaces. Windowfrostformswhenaglasswindowisexposedtocoldairoutsideand moistairinside.Windowfrostisfamiliartowinterresidentsofcoldclimates. Indoorheatandcoldoutdoortemperaturesformthistypeoffrost.Windowfrost wasmuchmorecommonbeforepeoplebeganusingdouble-panedwindows. Rimeisfrostthatformsquickly,usuallyinverycold,wetclimates.Rimealso formsinwindyweather.Rimesometimeslookslikesolidice.Shipstraveling throughcoldplacesliketheArcticOceanoftenendupwithrimecoveringat leastpartoftheexposedpartoftheship. FrostandPeople Frostcanseverelydamagecrops.Itcandestroyplantsorfruits.Plantswiththin skins,suchastomatoes,soy,orzucchini,canberuined.Iffrostisbadenough, potatoeswillfreezeintheground.Farmershavehadentirefieldsdestroyedin justafewfrostynights. Farmerstypicallyconsultalmanacsandmapstopredictfrost.Mapsand informationfromalmanacs(suchaspreviousdaysoffrost)tellfarmerswhat areasusuallyreceivefrost,howoftenitoccurs,andhowlongitlasts.These toolsarereliablebutarenotalwaysaccurate. Althoughfarmersstillrelyontheweather,manyspraytheircropstoreduce frostdamage.Thissprayusuallycontainsageneticallymodifiedorganism (GMO),anorganismwhosegeneshavebeenalteredbypeople.TheGMOthat reducesfrostdamagetocropsiscalledice-minusbacteria.Ice-minusbacteria makeitdifficultforicecrystalstoform.Ice-minusbacteriadonodamagetothe plant. Manyfarmersalsoprotecttheircropsbyusingtheselectiveinvertedsink(SIS) 2of6 method.Theselectiveinvertedsinkisalargefanthatdrawscold,moistairup intoachimney.Thechimneyexpelsthecoldairfarabovethecrops.This protectscropsfromfrostwithoutsprayingthem. Sturdierplantsarenotdestroyedbyfrost,butfrostwillstopthemfromgrowing. Evergreentrees,suchaspineandspruce,willstopgrowingduringafrost,but theywon'tdie. Roadscanalsobedamagedbyfrost.Frostyroadsareslipperyand,exposedto theheatfromcars,quicklybecomewet.Manydrivershavetroublenavigating frostyorwetroads. Vocabulary Term accurate Partof Definition Speech adjectiveexact. advectionfrost noun icecrystalsshapedlikespikesthatformfromacold wind. air noun layerofgasessurroundingEarth. almanac noun Antarctic noun ArcticOcean noun climate noun crop noun delicate adjectivefragileoreasilydamaged. dense havingpartsormoleculesthatarepackedclosely adjective together. annualpublicationcontainingacalendar,astronomical information,andweatherforecasts. regionatEarth'sextremesouth,encompassedbythe AntarcticCircle. oneofEarth'sfouroceans,borderedbyAsia,Europe, andNorthAmerica. allweatherconditionsforagivenlocationovera periodoftime. agriculturalproduce. 3of6 Term Partof Definition Speech temperatureatwhichwaterintheaircondensesto dewpoint noun evergreen noun treethatdoesnotloseitsleaves. expel verb toejectorforceout. farmer noun personwhocultivateslandandraisescrops. fog noun cloudsatgroundlevel. freeze noun frost noun frostflower noun fruit noun formwaterdropletsonobjectsneartheground. weatherpatternoftemperaturesbelow0degrees Celsius(32degreesFahrenheit). thincoatoficecoveringobjectswhenthedewpointis belowfreezing. icecrystalsthatformfrommoisturereleasedbya plantstemortree. ediblepartofaplantthatgrowsfromaflower. stateofmatterwithnofixedshapethatwillfillany gas noun containeruniformly.Gasmoleculesareinconstant, randommotion. gene noun genetically modified noun organism(GMO) partofDNAthatisthebasicunitofheredity. livingthingwhosegenes(DNA)havebeenalteredfor aspecificpurpose. brittle,transparentsubstancemadefrommeltedand glass noun hoarfrost noun ice noun waterinitssolidform. icecrystal noun solidicearrangedinprecisemolecularform. noun organismthatmakesitdifficultforfrosttoform. ice-minus bacteria map noun fusedmineralssuchassilica. icecrystalsthatformaswatervapornearobjects becomessolid.Alsocalledradiationfrost. symbolicrepresentationofselectedcharacteristicsof aplace,usuallydrawnonaflatsurface. 4of6 Term Partof Definition Speech moisture noun molecule noun mountain noun pane noun pine noun typeofevergreentreewithneedle-shapedleaves. potato noun plantnativetotheAmericas. predict verb toknowtheoutcomeofasituationinadvance. radiationfrost noun refrigerator noun reliable adjectivedependableorconsistent. rhyme noun rime noun icecrystalsthatforminwet,windyconditions. sailor noun personwhoworksaboardaship. noun (1772-1834)Englishpoet. SamuelTaylor Coleridge saturate verb selective invertedsink noun (SIS) wetness. smallestphysicalunitofasubstance,consistingoftwo ormoreatomslinkedtogether. landmassthatformsastectonicplatesinteractwith eachother. sheetofglassorothermaterialplacedinaframefor awindow. icecrystalsthatformaswatervapornearobjects becomessolid.Alsocalledhoarfrost. spacewithartificiallyloweredtemperature. wordthathasthesameendingsoundasanother word. tofillonesubstancewithasmuchofanother substanceasitcantake. methodofpreventingorreducingfrostdamageto cropsbyfanningcold,moistairupachimney. soy noun beans,orfruit,ofthesoybeanplant,nativetoAsia. spruce noun coniferous,orcone-bearing,tree. temperature noun degreeofhotnessorcoldnessmeasuredbya thermometerwithanumericalscale. 5of6 Term Partof Definition Speech tomato noun vapor noun plantandfruitnativetotheAmericas.Alsoconsidered avegetable. visibleliquidsuspendedintheair,suchasfog. stateoftheatmosphere,includingtemperature, weather noun atmosphericpressure,wind,humidity,precipitation, andcloudiness. movementofair(fromahighpressurezonetoalow wind noun pressurezone)causedbytheunevenheatingofthe Earthbythesun. icecrystalsthatformwhenawindowisexposedto windowfrost noun freezingtemperaturesononesideandmoistairon theother. zucchini noun typeofvegetable(squash).Alsocalledacourgette. Articles&Profiles SnowCrystals.com:GuidetoFrost Audio&Video NationalGeographicMusic:ChrisNormanEnsemble,IntheFieldofFrostand Snow Maps NOAA:Freeze/FrostMaps ©1996–2017NationalGeographicSociety.Allrightsreserved. 6of6