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WindisthemovementofaircausedbytheunevenheatingoftheEarthbythe
sun.Itdoesnothavemuchsubstance—youcannotseeitorholdit—butyoucan
feelitsforce.Itcandryyourclothesinsummerandchillyoutothebonein
winter.Itisstrongenoughtocarrysailingshipsacrosstheoceanandriphuge
treesfromtheground.Itisthegreatequalizeroftheatmosphere,transporting
heat,moisture,pollutants,anddustgreatdistancesaroundtheglobe.
Landforms,processes,andimpactsofwindarecalledAeolianlandforms,
processes,andimpacts.
Differencesinatmosphericpressuregeneratewinds.AttheEquator,thesun
warmsthewaterandlandmorethanitdoestherestoftheglobe.Warm
equatorialairriseshigherintotheatmosphereandmigratestowardthepoles.
Thisisalow-pressuresystem.Atthesametime,cooler,denserairmovesover
Earth’ssurfacetowardtheEquatortoreplacetheheatedair.Thisisahighpressuresystem.Windsgenerallyblowfromhigh-pressureareastolowpressureareas.
Theboundarybetweenthesetwoareasiscalledafront.Thecomplex
relationshipsbetweenfrontscausedifferenttypesofwindandweather
patterns.
Prevailingwindsarewindsthatblowfromasingledirectionoveraspecificarea
oftheEarth.Areaswhereprevailingwindsmeetarecalledconvergencezones.
Generally,prevailingwindsbloweast-westratherthannorth-south.This
happensbecauseEarth’srotationgenerateswhatisknownastheCoriolis
effect.TheCorioliseffectmakeswindsystemstwistcounter-clockwiseinthe
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NorthernHemisphereandclockwiseintheSouthernHemisphere.
TheCorioliseffectcausessomewindstotravelalongtheedgesofthehighpressureandlow-pressuresystems.Thesearecalledgeostrophicwinds.In
1857,DutchmeteorologistChristophBuysBallotformulatedalawabout
geostrophicwinds:WhenyoustandwithyourbacktothewindintheNorthern
Hemisphere,lowpressureisalwaystoyourleft.(IntheSouthernHemisphere,
low-pressuresystemswillbeonyourright.)
WindZones
TheEarthcontainsfivemajorwindzones:polareasterlies,westerlies,horse
latitudes,tradewinds,andthedoldrums.
PolarEasterlies
Polareasterliesaredry,coldprevailingwindsthatblowfromtheeast.They
emanatefromthepolarhighs,areasofhighpressurearoundtheNorthand
SouthPoles.Polareasterliesflowtolow-pressureareasinsub-polarregions.
Westerlies
Westerliesareprevailingwindsthatblowfromthewestatmidlatitudes.They
arefedbypolareasterliesandwindsfromthehigh-pressurehorselatitudes,
whichsandwichthemoneitherside.Westerliesarestrongestinthewinter,
whenpressureoverthepoleislow,andweakestinsummer,whenthepolar
highcreatesstrongerpolareasterlies.
Thestrongestwesterliesblowthroughthe“RoaringForties,”awindzone
between40and50degreeslatitudeintheSouthernHemisphere.Throughout
theRoaringForties,therearefewlandmassestoslowwinds.ThetipofSouth
AmericaandAustralia,aswellastheislandsofNewZealand,aretheonlylarge
landmassestopenetratetheRoaringForties.ThewesterliesoftheRoaring
FortieswereveryimportanttosailorsduringtheAgeofExploration,when
explorersandtradersfromEuropeandwesternAsiausedthestrongwindsto
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reachthespicemarketsofSoutheastAsiaandAustralia.
Westerlieshaveanenormousimpactonoceancurrents,especiallyinthe
SouthernHemisphere.Drivenbywesterlies,thepowerfulAntarcticCircumpolar
Current(ACC)rushesaroundthecontinent(fromwesttoeast)atabout4
kilometersperhour(2.5milesperhour).Infact,anothernamefortheAntarctic
CircumpolarCurrentistheWestWindDrift.TheACCisthelargestocean
currentintheworld,andisresponsiblefortransportingenormousvolumesof
cold,nutrient-richwatertotheocean,creatinghealthymarineecosystemsand
foodwebs.
HorseLatitudes
Thehorselatitudesareanarrowzoneofwarm,dryclimatesbetweenwesterlies
andthetradewinds.Horselatitudesareabout30and35degreesnorthand
south.Manydeserts,fromtherainlessAtacamaofSouthAmericatothearid
KalahariofAfrica,arepartofthehorselatitudes.
Theprevailingwindsatthehorselatitudesvary,butareusuallylight.Even
strongwindsareoftenshortinduration.
TradeWinds
Tradewindsarethepowerfulprevailingwindsthatblowfromtheeastacross
thetropics.Tradewindsaregenerallyverypredictable.Theyhavebeen
instrumentalinthehistoryofexploration,communication,andtrade.Ships
reliedontradewindstoestablishquick,reliableroutesacrossthevastAtlantic
and,later,PacificOceans.Eventoday,shippingdependsontradewindsandthe
oceancurrentstheydrive.
In1947,NorwegianexplorerThorHyerdahlandasmallcrewusedtradewinds
totravelfromthecoastofPerutothecoralreefsofFrenchPolynesia,more
than6,920kilometers(4,300miles),inasail-poweredraft.Theexpedition,
namedaftertheraft(Kon-Tiki)aimedtoprovethatancientmarinerscouldhave
usedpredictabletradewindstoexplorewidestretchesofthePacific.
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Tradewindsthatformoverland(calledcontinentaltradewinds)arewarmer
anddrierthanthosethatformovertheocean(maritimetradewinds).The
relationshipbetweencontinentalandmaritimetradewindscanbeviolent.
Mosttropicalstorms,includinghurricanes,cyclones,andtyphoons,developas
tradewinds.Differencesinairpressureovertheoceancausethesestormsto
develop.Asthedense,moistwindsofthestormencounterthedrierwindsof
thecoast,thestormcanincreaseinintensity.
Strongtradewindsareassociatedwithalackofprecipitation,whileweaktrade
windscarryrainfallfarinland.Themostfamousrainpatternintheworld,the
SoutheastAsianmonsoon,isaseasonal,moisture-ladentradewind.
Besidesshipsandrainfall,tradewindscanalsocarryparticlesofdustandsand
forthousandsofkilometers.ParticlesfromSaharansandandduststormscan
blowacrossislandsintheCaribbeanSeaandtheU.S.stateofFlorida,more
than8,047kilometers(5,000miles)away.
Duststormsinthetropicscanbedevastatingforthelocalcommunity.Valuable
topsoilisblownawayandvisibilitycandroptoalmostzero.Acrosstheocean,
dustmakestheskyhazy.Theseduststormsareoftenassociatedwithdry,lowpressureareasandalackoftropicalstorms.
Doldrums
Theplacewheretradewindsofthetwohemispheresmeetiscalledthe
intertropicalconvergencezone(ITCZ).TheareaaroundtheITCZiscalledthe
doldrums.Prevailingwindsinthedoldrumsareveryweak,andtheweatheris
unusuallycalm.
TheITCZstraddlestheEquator.Infact,thelow-pressuredoldrumsarecreated
asthesunheatstheequatorialregionandcausesairmassestoriseandtravel
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northandsouth.(Thiswarm,low-pressureequatorialwinddescendsagain
aroundthehorselatitudes.Someequatorialairmassesreturntothedoldrums
astradewinds,whileotherscirculateintheotherdirectionaswesterlies.)
Althoughmonsoonsimpacttropicalaswellasequatorialregions,thewinditself
iscreatedastheITCZmovesslightlyawayfromtheEquatoreachseason.This
changeinthedoldrumsdisturbstheusualairpressure,creatingthemoistureladenSoutheastAsianmonsoon.
ResultsofWind
Windtravelingatdifferentspeeds,differentaltitudes,andoverwaterorland
cancausedifferenttypesofpatternsandstorms.
JetStreams
Jetstreamsaregeostrophicwindsthatformneartheboundariesofairmasses
withdifferenttemperaturesandhumidity.TherotationoftheEarthandits
unevenheatingbythesunalsocontributetotheformationofhigh-altitudejet
streams.
Thesestrong,fastwindsintheupperatmospherecanblow480kph(298mph).
Jetstreamsblowthroughalayeroftheatmospherecalledthestratosphere,at
altitudesof8to14kilometers(5to9miles)aboveEarth’ssurface.
Thereislittleturbulenceinthestratosphere,whichiswhycommercialairline
pilotsliketoflyinthislayer.Ridingwithjetstreamssavestimeandfuel.Have
youeverheardsomeonetalkaboutaheadwindortailwindwhentheyare
talkingaboutairplanes?Thesearejetstreams.Iftheyarebehindtheplane,
pushingitforward,theyarecalledtailwinds.Theycanhelpyougettoyour
destinationmorequickly.Ifthewindsareinfrontoftheplane,pushingitback,
theyarecalledheadwinds.Strongheadwindscancauseflightdelays.
Hurricane
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Ahurricaneisagiant,spiralingtropicalstormthatcanpackwindspeedsofover
257kph(160mph)andunleashmorethan9trillionliters(2.4trilliongallons)of
rain.ThesesametropicalstormsareknownashurricanesintheAtlanticOcean,
cyclonesinthenorthernIndianOcean,andtyphoonsinthewesternPacific
Ocean.
Thesetropicalstormshaveaspiralshape.Thespiral(swirlingcounter-clockwise
intheNorthernHemisphereandclockwiseintheSouthernHemisphere)
developsasahigh-pressureareatwistsaroundalow-pressurearea.
TheAtlanticOcean’shurricaneseasonpeaksfrommid-AugusttolateOctober
andaveragesfivetosixhurricanesperyear.
Windconditionsthatcanleadtohurricanesarecalledtropicaldisturbances.
Theybegininwarmoceanwaterswhenthesurfacetemperaturesareatleast
26.6degreesCelsius(80degreesFahrenheit).Ifthedisturbancelastsformore
than24hoursandgetstospeedsof61kph(38mph),itbecomesknownasa
tropicaldepression.
Whenatropicaldepressionspeedsupto63-117kph(39-73mph),itisknownas
atropicalstorm,andisgivenaname.Meteorologistsnamethestormsin
alphabeticalorder,andalternatewithfemaleandmalenames.
Whenastormreaches119kph(74mph),itbecomesahurricaneandisrated
from1to5inseverityontheSaffirSimpsonscale.ACategory5hurricaneisthe
strongeststormpossibleontheSaffir-Simpsonscale.WindsofaCategory5
blowat252kph(157mph).
Hurricanesspinaroundalow-pressure(warm)centerknownasthe“eye.”
Sinkingairinsidetheeyemakesitverycalm.Theeyeissurroundedbyaviolent
circular“eyewall.”Thisiswherethestorm’sstrongestwindsandrainare.
HurricaneEthel,thestrongesthurricaneinrecordedhistory,roaredacrossthe
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GulfofMexicoinSeptember1960.Windsweresustainedat260kph(160mph).
However,HurricaneEthelquicklydissipated.Althoughitswindsultimatelyblew
asfarnorthastheU.S.statesofOhioandKentucky,bythetimeithitthe
coastlineoftheU.S.statesofLouisianaandMississippi,thestormsurgewas
onlyabout1.5meters(5feet).OnlyonepersondiedasaresultofHurricane
Ethel,anddamagetobuildingsandboatswaslimitedtolessthan$2million.
Hurricanesbringdestructiontocoastalecosystemsandcommunities.Whena
hurricanereachesland,itoftenproduceswavesthatcanreach6meters(20
feet)highandbepushedbyhighwinds161kilometers(100miles)inland.These
stormsurgesareextremelydangerousandcause90percentofallhurricane
deaths.
ThedeadliesthurricaneonrecordistheGreatHurricaneof1780.Although
sophisticatedmeteorologicalequipmentwasnotavailableatthattime,winds
mayhavereached320kph(200mph)asthehurricanehitBarbadosandother
islandsintheCaribbeanSea.Thismayhavebeenenoughtostripthebarkfrom
trees.Morethan20,000peoplediedasaresultofthehurricaneasitmadeits
wayacrossBarbados,St.Lucia,Martinique,Dominica,Guadeloupe,Dominican
Republic,Bahamas,TurksandCaicos,andBermuda.Althoughitdecreasedin
intensity,thehurricanewastrackedthroughtheU.S.stateofFloridabefore
dissipatingintheCanadianprovinceofNewfoundland.
Hurricanescanbedestructiveinotherways.Highwindscancreatetornadoes.
Heavyrainscontributetofloodsandlandslides,whichmayoccurmany
kilometersinland.Damagetohomes,businesses,schools,hospitals,roads,and
transportationsystemscandevastatecommunitiesandentireregions.
HurricaneKatrina,whichblewthroughtheGulfofMexicoandintothesouthern
U.S.in2005,isthemostexpensivehurricaneinrecordedhistory.Damageto
buildings,vehicles,roads,andshippingfacilitiesisestimatedatabout$133.8
billion(adjustedforinflation).NewOrleans,Louisiana,wasalmostcompletely
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devastatedbyHurricaneKatrina.NewOrleans,aswellasMobile,Alabama,and
Gulfport,Mississippi,tookyearstorecoverfromthedamagedonetotheir
structuresandinfrastructure.
Thebestdefenseagainstahurricaneisanaccurateforecastthatgivespeople
timetogetoutofitsway.TheNationalHurricaneCenterissueshurricane
watchesforstormsthatmayendangercommunities,andhurricanewarnings
forstormsthatwillreachlandwithin24hours.
Cyclones
CyclonesblowthroughtheIndianOceaninthesamewayhurricanesblow
acrosstheAtlantic.Cyclonesblowinwithairmassesfromtheeast,oftenthe
SouthChinaSea,orthesouth.
Themostpowerfulanddevastatingcycloneinrecordedhistorywasthe1970
BholaCyclone.LikeHurricaneKatrina,theBholaCyclonewasaCategory3
storm.Itswindswereabout185kph(115mph)asitmadelandfallalongthe
coastoftheBayofBengal,inwhatistodayBangladesh.Morethan300,000
peopledied,andmorethanamillionweremadehomeless.Cyclonewinds
devastatedfishingvillages,andstormsurgesdrownedcrops.Economicdamage
fromtheBholaCyclonewasmorethan$479million,adjustedforinflation.
Typhoon
TyphoonsaretropicalstormsthatdevelopoverthenorthwestPacificOcean.
Theirformationisidenticaltohurricanesandcyclones.Typhoonsformas
equatorialwindsandblowwestwardbeforeturningnorthandmergingwith
westerliesaroundthemid-latitudes.
TyphoonscanimpactawideareaoftheeasternPacific.Theislandsofthe
Philippines,China,Vietnam,andJapanarethemostaffected.However,
typhoonshavealsobeenrecordedasfarastheU.S.statesofHawaiiandeven
Alaska.
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Typhoonsareoftenassociatedwithextremelyheavyrainfall.Thewettest
typhooneverrecordedwasTyphoonMorakotin2009.Morakotdevastatedthe
entireislandofTaiwan,withwindsofabout140kph(85mph).Stormsurgesand
floodscausedbythosewinds,however,causedthemostdamage.Morethan
277centimeters(109inches)ofraindrenchedTaiwan,leadingto461deaths
and$6.2billionindamage.
Nor’eastersandBlizzards
Anor'easterisastrongwinterstormcombiningheavysnowfall,strongwinds,
andverycoldtemperatures.ItblowsfromthenortheastalongtheEastCoastof
theU.S.andCanada.Astrongnor’easteriscalledablizzard.
TheU.S.WeatherServicecallsastormablizzardwhenthestormhaswind
speedsofmorethan56kph(35mph)andlowvisibility.(Visibilityisthedistance
thatapersoncansee—blizzards,likefog,makevisibilitydifficultandatasklike
drivingdangerous.)Thestormmustgoonforaprolongedperiodoftimetobe
classifiedasablizzard,usuallyafewhours.
Blizzardscanisolateandparalyzeareasfordays,especiallyiftheareararely
hassnowfallanddoesnothavetheequipmenttoclearitfromthestreets.
TheGreatBlizzardof1888wasperhapstheworstinU.S.recordedhistory.
Windsofupto72kph(45mph)whippedtheEastCoastfromChesapeakeBay
toasfarnorthasNovaScotia,Canada.Morethan147centimeters(58inches)
ofsnowfellacrosstheregion,causingfreezingtemperaturesandmassive
floodingasthesnowmelted.TheGreatBlizzardresultedin400deathsand$1.2
billionindamage.
Monsoon
Amonsoonisaseasonalchangeintheprevailingwindsystemofanarea.They
alwaysblowfromcold,high-pressureregions.Monsoonsarepartofayearlong
cycleofunevenheatingandcoolingoftropicalandmid-latitudecoastalregions.
MonsoonsarepartoftheclimateofAustralia,SoutheastAsia,andinthe
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southwesternregionofNorthAmerica.
Theairoverlandisheatedandcooledmorequicklythantheairovertheocean.
Duringsummer,thismeanswarmland-airrises,creatingaspaceforthecool
andmoistairfromtheocean.Asthelandheatsthemoistair,itrises,cools,
condenses,andfallsbacktoEarthasrain.Duringthewinter,landcoolsmore
quicklythantheocean.Thewarmairovertheoceanrises,allowingcoolland-air
toflowin.
Mostwintermonsoonsarecoolanddry,whilesummermonsoonsarewarmand
moist.Asia’swintermonsoonsbringcool,dryairfromtheHimalayamountains.
Thefamoussummermonsoon,ontheotherhand,developsovertheIndian
Ocean,absorbingtremendousamountsofmoisture.Summermonsoonsbring
warmthandprecipitationtoIndia,SriLanka,Bangladesh,andMyanmar.
ThesummermonsoonisessentialforthehealthandeconomiesoftheIndian
subcontinent.Aquifersarefilled,allowingwaterfordrinking,hygiene,industry,
andirrigation.
Tornado
Atornado,alsocalledatwister,isaviolentlyrotatingfunnelofair.Tornadoes
canoccurindividuallyorinmultiples,astwospinningvortexesofairrotating
aroundeachother.Tornadoescanoccuraswaterspoutsorlandspouts,spinning
fromhundredsofmetersintheairtoconnectthelandorwaterwithclouds
above.Althoughdestructivetornadoescanoccuratanytimeofday,mostof
themoccurbetween4and9p.m.localtime.
Tornadoesoftenoccurduringintensethunderstormscalledsupercells.A
supercellisathunderstormwithapowerful,rotatingupdraft.(Adraftissimplya
verticalmovementofair.)Thispowerfulupdraftiscalledamesocyclone.
Amesocyclonecontainsrotatingdraftsofair1to10kilometers(1to6miles)in
theatmosphere.Whenrainfallincreasesinthesupercell,raincandragthe
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mesocyclonesdownwithittotheground.Thisdowndraftisatornado.
Dependingonthetemperatureandmoistureoftheair,atornadocanlastafew
minutesoroveranhour.However,coolwinds(calledrearflankdowndrafts)
eventuallywraparoundthetornadoandcutoffthesupplyofwarmairthat
feedsit.Thetornadothinsoutintothe“rope-like”stageanddissipatesafew
minuteslater.
Mosttornadoeshavewindspeedsoflessthan177kph(110mph),andare
about76meters(250feet)across.Theycantravelforseveralkilometers
beforedissipating.However,themostpowerfultornadoescanhavewind
speedsofmorethan482kph(300mph)andbemorethan3kilometers(2
miles)across.Thesetornadoescantravelacrossthegroundfordozensof
kilometersandthroughseveralstates.
Theseviolentstormsoccuraroundtheworld,buttheUnitedStatesisamajor
hotspotwithaboutathousandtornadoeseveryyear."TornadoAlley,"aregion
thatincludeseasternSouthDakota,southernMinnesota,Nebraska,Kansas,
Oklahoma,northernTexas,andeasternColorado,ishometothemostpowerful
anddestructiveofthesestorms.
ThemostextremetornadoeverrecordedoccurredonMarch18,1925.This
“Tri-StateTornado”spedfor338kilometers(219miles)throughMissouri,
Illinois,andIndiana.Thetornadodestroyedlocalcommunications,making
warningsforthenexttownnearlyimpossible.TheTri-StateTornadokilled695
peoplein3.5hours.
Thebestprotectionagainstatornadoisearlywarning.Inareaswhere
tornadoesarecommon,manycommunitieshavetornadowarningsystems.In
Minnesota,forexample,talltowersthroughoutneighborhoodssoundanalarmif
atornadoisnear.
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MeasuringWinds
Windisoftenmeasuredintermsofwindshear.Windshearisadifferencein
windspeedanddirectionoverasetdistanceintheatmosphere.Windshearis
measuredbothhorizontallyandvertically.Windshearismeasuredinmeters
persecondtimeskilometersofheight.Undernormalconditions,thewinds
movemuchfasterhigherintheatmosphere,creatinghighwindshearinhigh
altitudes.
Engineersmustconsideranarea’saveragewindshearwhenconstructing
buildings.Windshearishighernearthecoast,forexample.Skyscrapersmust
accountforthisincreasedwindbyhavingastrongerfoundationorbeing
engineeredtosafely“sway”withthewind.
Theamountofforcethatwindisgeneratingismeasuredaccordingtothe
Beaufortscale.ThescaleisnamedforSirFrancisBeaufort,whoestablisheda
systemfordescribingwindforcein1805fortheBritishRoyalNavy.The
Beaufortscalehas17levelsofwindforce.“0”describesconditionsthatareso
calmthatsmokerisesvertically.“12”describesahurricane,and“13-17”are
reservedonlyfortropicaltyphoons,themostpowerfulandpotentially
destructivewindsystems.
Ananemometerisadeviceformeasuringwindspeed.Anemometersareused
withtornadodatacollectors,whichmeasurethevelocity,precipitation,and
pressureoftornadoes.
Tornadoes’strengthismeasuredaccordingtotheFujitascale.Thescalehassix
categoriesthatdesignateincreasingdamage.Afterthetornadohaspassed,
meteorologistsandengineersdeterminethetornado’sstrengthbasedonits
windspeed,width,anddamagetovegetationandhuman-builtstructures.In
2007,theEnhancedFujitaScalewasestablishedintheU.S.;itprovidesmore
specificeffectsofthetornadotodetermineitsdestructivepower.TheEnhanced
FujitaScalehas28categories,withthestrongestcatalogingdamageto
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hardwoodandsoftwoodtrees.
HurricanesaremeasuredusingtheSaffir-Simpsonscale.Inadditiontotropical
depressionsandtropicalstorms,therearefivecategoriesofhurricanes.The
mostpowerful,Category5,ismeasuredbywindswhippingat252kph(157
mph).Tropicalcyclonesandtyphoonsareoftenmeasuredusingotherscales,
suchasJapan’sTropicalCycloneIntensityScale,whichmeasuresatyphoonas
windsat118kph(73mph).
ImpactonClimate
Windisamajorfactorindeterminingweatherandclimate.Windcarriesheat,
moisture,pollutants,andpollentonewareas.
Manydailyweatherpatternsdependonwind.Acoastalregion,forinstance,
undergoeschangesinwinddirectiondaily.Thesunheatsthelandmorequickly
thanthewater.Warmairabovethelandrises,andcoolerairabovethewater
movesinovertheland,creatinganinlandbreeze.Coastalcommunitiesare
usuallymuchcoolerthantheirinlandneighbors.SanFranciscoisacoastalcity
in“sunnyCalifornia,”andyettheauthorMarkTwainnoticedthat“thecoldest
winterIeverspentwasasummerinSanFrancisco!”
Windaffectstheclimateofamountainousareadifferently.Rainshadowsare
createdaswindinteractswithamountainrange.Aswindapproachesa
mountain,itbringsmoisturewithit,whichcondensesasrainandother
precipitationbeforecomingoverthecrestofthemountain.Ontheothersideof
themountain,dry“downslopewinds”canspeedthroughmountainpassesat
nearly160kph(100mph).Oneofthemostfamiliarofthesedownslopewindsis
theFöhn.Föhnwinds—nicknamed“snow-eaters”—developasairdescendsover
theAlps,creatingawarmerclimateincentralEurope.
Windsalsohelpdriveoceansurfacecurrentsaroundtheworld.TheAntarctic
CircumpolarCurrenttransportscold,nutrient-richwateraroundAntarctica.The
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GulfStreambringswarmwaterfromtheGulfofMexicouptheEastCoastof
NorthAmericaandacrosstheAtlantictoNorthernEurope.DuetotheGulf
Stream,NorthernEuropeenjoysamuchwarmer,milderclimatethanother
areasatsimilarlatitudes,suchastheU.S.stateofAlaska.
ImpactonEcology
Windhasthepowertomoveparticlesofearth—usuallydustorsand—ingreat
quantities,andoverfardistances.DustfromtheSaharacrossestheAtlanticto
createhazysunsetsintheCaribbean.
Windstransportvolcanicashanddebrisforthousandsofkilometers.Winds
carriedashfromthe2010eruptionofEyjafjallajökull,avolcanoinIceland,asfar
westasGreenlandandasfareastasGreatBritain.Themassive1883eruption
ofKrakatoa,anislandvolcanoinIndonesia,hadevenmoredramatic
atmosphericresults.Windscarriedvolcanicashanddebrishighinthe
atmosphereacrosstheglobe.Europeenduredyearsofcold,dampsummers
andpinksunsets.
Wind’sabilitytomoveearthcanerodethelandscape.Insomecases,thistakes
placesinthedesert,assanddunesmigrateandchangeshapeovertime.The
windcanalsopickupmassiveamountsofsandand“sandblast”rockformations
intostunningsculptures.TheAltiplanoregionofSouthAmericahasdramatically
shapedventifacts—rockscarvedbythewind-drivensandandice.
Thewind’spowertoerodethelandcanbedetrimentaltoagriculture.Loess,a
sedimentthatcandevelopintooneoftherichestsoilsforfarming,iseasily
sweptupbywind.Evenwhenfarmerstakeprecautionstoprotectit,thewind
canerodeupto2.5kilogramsofloesspersquaremeter(1.6poundpersquare
foot)everyyear.
ThemostfamousexampleofthisdevastatingwindstormisprobablytheDust
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Bowlof1930sNorthAmerica.DustBowlstormscouldreducevisibilitytoafew
feet,andearnednameslike"BlackBlizzards."Millionsoffarmers,especially
thoseintheU.S.statesofOklahoma,Arkansas,andTexas,losttheirlandwhen
theywereunabletoharvestanycrops.
Howeverdevastatingtotheeconomy,windisanimportantwayplantsdisperse
seeds.Thisformofseeddispersaliscalledanemochory.Plantsthatrelyon
anemochoryproducehundredsandeventhousandsofseeds.Seedsarecarried
bythewindtodistantornearbyplaces,increasingthespreadoftheplant’s
genetics.Someofthemostfamiliarseedsdispersedbythewindarethoseof
thefuzzydandelion.
WindEnergy
Windhasbeenusedasasourceofenergyformorethanathousandyears—it
haspushedshipsaroundtheglobeandbeencapturedinwindmillstopump
water;ithasturnedgiantstonestogrindgrains,makepaper,sawlogs,and
crushore.Today,mostwindenergyisusedtogenerateelectricityforhomes,
businesses,hospitals,schools,andindustry.
Windisarenewableresourcethatdoesnotdirectlycausepollution.Wind
energyisharnessedthroughpowerfulturbines.Windturbineshaveatalltubular
towerwithtwoorthreepropeller-likebladesrotatingatthetop.Whenthewind
turnstheblades,thebladesturnageneratorandcreateelectricity.
Often,windturbinesarecollectedinwindyareasinarraysknownaswindfarms.
Manywindfarmshavebeenestablishedonmountains,invalleys,andoffshore,
astheairfromtheoceaninteractswithland-air.
Somepeoplethinkwindturbinesareuglyandcomplainaboutthenoisethey
make.Theslowlyrotatingbladescanalsokillbirdsandbats—butnotnearlyas
manyascars,powerlines,andhigh-risebuildings.
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Theeconomicdrawbacktowindfarms,however,isthewinditself.Ifit'snot
blowing,there'snoelectricitygenerated.
Still,useofwindenergyhasmorethanquadrupledbetween2000and2006.
Germanyhasthemostinstalledwindenergycapacity,followedbySpain,the
UnitedStates,India,andDenmark.Developmentisalsogrowingquicklyin
FranceandChina.
Industryexpertspredictthatifthispaceofgrowthcontinues,by2050,one-third
oftheworld’selectricityneedscouldbemetbywind.
Vocabulary
Term
aeolian
landform
Ageof
Exploration
airmass
Partof
Definition
Speech
noun
noun
noun
geographicfeaturecreatedbywind.
(1400s-1800s)periodduringwhichEuropeanstraveled
theworldbyoceaninsearchoftrade.
alargevolumeofairthatismostlyconsistent,
horizontally,intemperatureandhumidity.
anemochory noun
processofseedsbeingdispersedbythewind.
anemometer noun
adevicethatmeasureswindspeed.
Antarctic
mostpowerfulsurfaceoceancurrentintheworld,which
Circumpolar noun
rotatesclockwisearoundthecontinentofAntarctica.Also
Current(ACC)
calledtheWestWindDrift.
aquifer
noun
atmosphere
noun
Beaufort
scale
noun
anundergroundlayerofrockorearthwhichholds
groundwater.
layersofgasessurroundingaplanetorothercelestial
body.
scalemeasuringwindforces,generallyfrom0to12.
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Term
Partof
blizzard
noun
climate
noun
condense
verb
convergence
zone
Definition
Speech
noun
stormwithhighwinds,intensecold,heavysnow,andlittle
rain.
allweatherconditionsforagivenlocationoveraperiod
oftime.
toturnfromgastoliquid.
areawhereprevailingwindsfromdifferentareasmeet
andinteract.
theresultofEarth'srotationonweatherpatternsand
Corioliseffectnoun
oceancurrents.TheCorioliseffectmakesstormsswirl
clockwiseintheSouthernhemisphereand
counterclockwiseintheNorthernHemisphere.
current
noun
steady,predictableflowoffluidwithinalargerbodyof
thatfluid.
weathersystemthatrotatesaroundacenteroflow
cyclone
noun
pressureandincludesthunderstormsandrain.Usually,
hurricanesrefertocyclonesthatformovertheAtlantic
Ocean.
detrimental
adjectiveharmful.
devastate
verb
todestroy.
dissipate
verb
toscatteranddisappear.
doldrums
noun
draft
noun
dune
noun
dust
noun
electricity
noun
emanate
verb
areasofcalmwindsnorthoftheEquatorinthePacific,
Atlantic,andIndianOceans.
verticallymovingaircurrent.
amoundorridgeofloosesandthathasbeendeposited
bywind.
tiny,dryparticlesofmaterialsolidenoughforwindto
carry.
setofphysicalphenomenaassociatedwiththepresence
andflowofelectriccharge.
tooriginateorproceedfromasource.
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Term
Partof
Definition
Speech
personwhoplansthebuildingofthings,suchas
engineer
noun
structures(constructionengineer)orsubstances
(chemicalengineer).
erode
verb
towearaway.
eyewall
noun
ringofthunderstormsthatsurroundsahurricane'seye.
forecast
verb
topredict,especiallytheweather.
front
noun
Fujitascale
noun
geostrophic
wind
noun
boundarybetweenairmassesofdifferenttemperatures
andhumidities.
scalethatmeasurestheintensityoftornadoes,fromF0
(weakest)toF5(strongest).
aircurrentthattravelsalongtheedgeofahigh-pressure
andlow-pressuresystem.
warmcurrentthatstartsintheGulfofMexicoandtravels
GulfStream
noun
alongtheeasterncoastoftheU.S.andCanadabefore
crossingtheNorthAtlanticOcean.
headwind
high-pressure
system
noun
usuallyslowingitdown.
weatherpatterncharacterizedbyhighairpressure,
noun
usuallyasaresultofcooling.High-pressuresystemsare
usuallyassociatedwithclearweather.
horselatitudenoun
humidity
windblowingintheoppositedirectionofamovingobject,
noun
parallelsbetween30and35degreesnorthandsouthof
theequatorthatexperienceverylittleprecipitation.
amountofwatervaporintheair.
tropicalstormwithwindspeedsofatleast119kilometers
hurricane
noun
(74miles)perhour.Hurricanesarethesamethingas
typhoons,butusuallylocatedintheAtlanticOcean
region.
hygiene
noun
scienceandmethodsofkeepingcleanandhealthy.
industry
noun
activitythatproducesgoodsandservices.
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Term
Partof
Definition
Speech
infrastructurenoun
Intertropical
Convergence noun
Zone(ITCZ)
structuresandfacilitiesnecessaryforthefunctioningofa
society,suchasroads.
beltoflow-pressureaircurrentsthatcircletheEarthat
theEquator.AlsoknownastheMonsoonZone.
irrigation
noun
wateringland,usuallyforagriculture,byartificialmeans.
jetstream
noun
windsspeedingthroughtheupperatmosphere.
loess
noun
windblownsoilorsilt.
low-pressure
system
weatherpatterncharacterizedbylowairpressure,
noun
usuallyasaresultofwarming.Low-pressuresystemsare
oftenassociatedwithstorms.
mesocyclone noun
meteorologistnoun
rotatingshaftofrapidlyrisingairwithinastorm.
personwhostudiespatternsandchangesinEarth's
atmosphere.
areabetweentheTropicofCancerandtheArcticCircle
midlatitude
noun
inthenorth,andbetweentheTropicofCapricornandthe
AntarcticCircleinthesouth.Alsocalledatemperate
zone.
seasonalchangeinthedirectionoftheprevailingwinds
monsoon
noun
ofaregion.Monsoonusuallyreferstothewindsofthe
IndianOceanandSouthAsia,whichoftenbringheavy
rains.
strong,cold,relativelydrywindblowingfromthe
nor'easter
noun
polar
plural
cold,dryprevailingwindsthatblowfromthepolarhighs
easterlies
noun
tolow-pressuresystemsinthewesterlies.
northeastdowntheEastCoastofNorthAmerica.
consistenthigh-pressuresystemaroundtheNorthor
polarhigh
noun
SouthPole.
pollution
noun
introductionofharmfulmaterialsintotheenvironment.
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Term
Partof
precipitation noun
predictable
prevailing
wind
resource
allformsinwhichwaterfallstoEarthfromthe
atmosphere.
adjectiveregularorabletobeforecasted.
noun
rainshadow noun
renewable
Definition
Speech
noun
windthatblowsfromonedirection.
drylandonthesideofamountainfacingawayfrom
prevailingwinds.
resourcethatcanreplenishitselfatasimilarratetoits
usebypeople.
rotation
noun
object'scompleteturnarounditsownaxis.
route
noun
pathorway.
Saffir
Simpson
noun
scale
systemthatclassifieshurricanestrength,fromCategory
1(weakest)toCategory5(strongest).
seed
noun
partofaplantfromwhichanewplantgrows.
shipping
noun
transportationofgoods,usuallybylargeboat.
stormsurge
noun
abnormalriseinsealevelaccompanyingahurricaneor
otherintensestorm.Alsocalledastormtide.
levelofEarth'satmosphere,extendingfrom10
stratosphere noun
kilometers(6miles)to50kilometers(31miles)abovethe
surfaceoftheEarth.
supercell
tailwind
noun
noun
topsoil
noun
tornado
noun
thunderstormwithastrong,rotatingupdraft
(mesocyclone)inthemiddle.
windcomingfromdirectlybehindamovingobject,
speedingitup.
themostvaluable,upperlayerofsoil,wheremost
nutrientsarefound.
aviolentlyrotatingcolumnofairthatformsatthe
bottomofacloudandtouchestheground.
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Term
Partof
Definition
Speech
windsthatblowtowardtheEquator,fromnortheastto
tradewind
noun
southwestintheNorthernHemisphereandfrom
southeasttonorthwestintheSouthernHemisphere.
tropical
depression
tropical
storm
tropics
turbine
noun
tropicalstormwithmaximumsustainedwindsnearthe
surfaceoflessthan63kilometers(39miles)perhour.
weatherpatternofswirlingwindsoveracenteroflow
noun
pressureabovewarmoceanwaters.Tropicalstormsare
lesspowerfulthancyclonesandhurricanes.
plural
noun
noun
regiongenerallylocatedbetweentheTropicofCancer
(231/2degreesnorthoftheEquator)andtheTropicof
Capricorn(231/2degreessouthoftheEquator).
machinethatcapturestheenergyofamovingfluid,such
asairorwater.
tropicalstormwithwindspeedsofatleast74miles(119
typhoon
noun
kilometers)perhour.Typhoonsarethesamethingas
hurricanes,butusuallylocatedinthePacificorIndian
Oceanregion.
velocity
noun
ventifact
noun
measurementoftherateanddirectionofchangeinthe
positionofanobject.
rockthathasbeenshapedbywind-drivensand,dust,or
iceparticles.
volcanicash noun
fragmentsoflavalessthan2millimetersacross.
vortex
noun
columnofrotatingfluid,suchasair(wind)orwater.
waterspout
noun
weather
pattern
Westerlies
columnofrotatingcloud-filledwindthatdescendstoan
oceanorlake.
repeatingorpredictablechangesintheEarth's
noun
atmosphere,suchaswinds,precipitation,and
temperatures.
plural
noun
windsblowingfromthewestacrossthemid-latitudes.
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Term
Partof
Definition
Speech
movementofair(fromahighpressurezonetoalow
wind
noun
pressurezone)causedbytheunevenheatingofthe
Earthbythesun.
windenergy noun
windfarm
noun
windmill
noun
windshear
noun
kineticenergyproducedbythemovementofair,ableto
beconvertedtomechanicalpower.
areawithalargegroupofwindturbines,usedto
generateelectricpower.
instrumentthatgeneratespowerfromtheforceofwind
rotatinglargeblades.
differenceinwindspeedanddirectionoverasetdistance
intheatmosphere.
Articles&Profiles
NationalGeographicEnvironment:WindPower
NationalGeographicScience:Wind
NationalWeatherService:OriginofWind
Interactives
NationalGeographicEnvironment:HarnessthePowerofWind
©1996–2017NationalGeographicSociety.Allrightsreserved.
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