新托福阅读复习材料美国科学文摘精选Word格式.docx
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新托福阅读复习材料美国科学文摘精选Word格式.docx
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upperatmospheremaydelayglobalozonerecovery.
NASAresearchershavefoundthatanincreaseinwatervaporinthe
stratosphere,stemmingpartiallyfromgreenhousegases,maydelayozone
recoveryandincreasetherateofclimatechange.
Tocheckonthelong-termstratosphericcoolingandozonedepletion,NASAput
datafromsatellitesandotherremotesensorsintoitsGISSglobalclimate
model.Itwasthefirststudytolinkgreenhousegasestoincreasedozone
depletionoverpopulatedareas.
Waterandozone.Climatemodelsshowcoolerstratospherictemperatureshappen
whenthereismorewatervaporpresent.Watervaporalsoleadstothe
breakdownofozonemolecules.
Thestratosphereisthedrylayeroftheatmosphereabovethetroposphere,
wheretemperaturesincreasewithheight.
Accordingtosatellitedata,upperatmospherictemperaturesaroundtheworld-
ataltitudesof20to35mileshigh--havecooledbetween5.4and10.8
degreesFahrenheitoverrecentdecades.
Drivingforces.NASAfoundtwodrivingforcesbehindthechangein
stratosphericmoisture:
Increasedemissionsofthegreenhousegasmethanearetransformedintowater
inthestratosphere,accountingforaboutathirdoftheobservedincrease
inmoisturethere.
Morewateristransportedfromtheloweratmosphere.Warmerairholdsmore
watervaporthancolderair,sotheamountofwatervaporinthelower
atmosphereincreasesasitiswarmedbythegreenhouseeffect.Greenhouse
gases,suchascarbondioxideandmethane,mayenhancethetransportof
waterintothestratosphere.
Theincreasedtransportofwatervaportothestratosphereseemslikelyto
havebeeninducedbyhumanactivities.
Ozonedestruction.Risinggreenhousegasemissionsaccountforallorpartof
thewatervaporincrease,whichcausesstratosphericozonedestruction.
Whenmorewatervaporworksitswayintothestratosphere,thewatermolecules
canbebrokendown,releasingreactivemoleculesthatcandestroyozone.If
thetrendofincreasingstratosphericwatervaporcontinues,itcouldincrease
futureglobalwarmingandimpedeozonestratosphericrecovery.
Theimpactonglobalwarmingcomesaboutbecausebothwatervaporandozone
aregreenhousegases,whichtrapheatleavingtheEarth.Whentheychange,the
Earth'
senergybalancechangestoo,alteringthesurfaceclimate.
Warmerground.Increasedwatervaporinthestratospheremakesitwarmeron
thegroundbytrappingheat,whiletheozonelossmakesitcolderonthe
ground.
Watervaporhasamuchlargereffect,sothatoverallthechangesincrease
globalwarming.
AlthoughozonedepletioncoolstheEarth'
ssurface,repairingstratospheric
ozoneisimportanttoblockharmfulultravioletradiation.Othergreenhouse
gasemissionsalsoneedtobereduced.
UARSsatellite.NASAcombinedsevenyearsofdatafromtheUpperAtmosphere
ResearchSatellite(UARS)HalogenOccultationExperiment(HALOE)withdata
collectedonthegroundtopaintacompletepictureoftheupperatmosphere.
NASA'
sHALOEwasaboardtheUARSspacecraftwhenitwaslaunchedSeptember12,
1991aspartoftheEarthScienceEnterpriseProgram.Thespacecraft'
smission
atlaunchwastoimproveunderstandingofstratosphericozonedepletionby
analyzingverticalprofilesofozone,hydrogenchloride,hydrogenfluoride,
methane,watervapor,nitricoxide,nitrogendioxide,andaerosols.
Fourteenyearsoflowerstratosphericmeasurementshaverevealedlarge
increasesinwatervapor.Thoughsomeolderstudiesconflictwithlower
stratosphericobservationsofwatervaportrends,newstudiesagreewiththe
increases,showingtheyhavebeentakingplaceformorethanfourdecades.
WhatIsAnOzoneHole?
Ozonemoleculesaremadeupofthreeatomsofoxygen.Theycompriseathin
layeroftheatmospherethatabsorbsharmfulultravioletradiationfromthe
Sun.
Mostatmosphericozoneisfoundbetweenapproximatelysixmilesand18miles
abovetheEarth'
ssurface.
Anozone"
hole"
iswhatscientistscallan"
ozonedepletionarea"
ofinthat
regionofEarth'
satmosphere.
Reallybighole.Thelargest-everozoneholewasdetectedonSeptember6,
2000,bytheTotalOzoneMappingSpectrometer(TOMS)aboardaNASAsatellite
knownasEarthProbe(TOMS-EP).
TheAntarcticozoneholeisthreetimeslargerthantheentirelandmassof
theUnitedStates,makingitthelargestsuchareaeverobserved.
Theholehadexpandedtoarecordsizeof11millionsquaremiles.The
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