气象科技英语翻译资料.docx
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气象科技英语翻译资料.docx
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气象科技英语翻译资料
Likeafishintheocean,manisconfinedtoaveryshallowlayerofatmosphere.ThegaseousenvelopeoftheEarthisphysicallyinhomogeneousinboththeverticalandhorizontaldirections,althoughthehorizontalinhomogeneityismuchlessmarkedthantheverticalinhomogeneity.
Variouscriteriahavebeendevisedfordividingtheatmosphereintolayers.Thisdivisioncanbebasedonthenatureoftheverticaltemperatureprofile,onthegaseouscompositionoftheairatdifferentaltitudes,andtheeffectoftheatmosphereonaircraftatdifferentaltitudes,etc.Thedivisionbasedonthevariationoftheairtemperaturewithaltitudeisusedmostcommonlyinthemeteorologicalliterature.
AccordingtoapublicationoftheagrologicalcommissionoftheWorldMeteorologicalOrganization(WMO)in1961,theEarth’satmosphere,isdividedintofivemainlayers:
thetroposphere,thestratosphere,themesosphere,thethermosphereandtheexosphere.Theselayersareboundedbyfourthintransitionregions:
thetropospause,thestratospause,themesospause,thethermospause.
ThetroposphereisthelowerlayeroftheatmospherebetweentheEarth’ssurfaceandthetropopause.Thetemperaturedropswithincreasingheightinthetroposphere,atameanrateof6.5℃perkilometer(lapserate).Theupperboundaryofthetroposphereliesataheightofapproximately8to12kminthepolarandtropospherecontainsabout75%ofthetotalmassofatmosphericair,whileinthetropicsitcontainsabout90%.Thetropoauseisanintermediatelayerinwhicheitheratemperatureinversionoranisothermaltemperaturedistributionisobserved.
Thestratosphereistheatmosphericlayerabovethetroposphere.Inthestratospherethetemperatureeitherincreaseswithheightorremainsnearlyconstant.Inthelowerpartofthestratosphere(uptoapproximately20kmabovetheEarth’ssurface)thetemperatureispracticallyconstant(about-56℃).Whilefurtherupthetemperatureincreaseswithaltitudeatarateofabout1℃/kmatheightsof20to30kmandabout2.8℃/kmataltitudesfrom32to47km.Underthestandardconditionsthetemperatureatthe47kmlevelisnormally-2.5℃.
ThisincreaseintemperaturewithheightisduetotheabsorptionofUVsolarradiationbyozonemolecules.Itshouldbenotedthatabout99%ofthetotalmassofatmosphericairisconcentratedinthetroposphereandstratosphere,whichextenduptoanlatitudeof30or35km.Thestratopauseisanintermediatelayerbetweenthestratosphereandthemesosphere(inthealtituderegionfrom47to52km),inwhichthetemperatureremainsconstantatabout0℃.
Thethermosphereistheatmosphericlayerabovethemesopause.Thetemperatureinthislayerincreaseswithincreasingaltitude,reachingabout2000℃atabout450km,themeanheightoftheupperboundaryofthethermosphere.ThetemperatureincreaseinthislayerismainlycausedbytheabsorptionofUVsolarradiationbyoxygenmolecules,whichdissociateasaresultofthis.
Theexosphereisthefurthestoutandtheleaststudiedpartoftheupperatmosphere.Itislocatedabove450kmaltitude.Theairdensityintheexosphereissolowthatatomsandmoleculescanescapefromitintointerplanetaryspace.
Finally,alongwiththeabovedivisionoftheatmosphere,wewillalsomakeuseofadivisionbasedontheextentofatmosphericinteractionwiththeEarth’ssurface.Accordingtothisprincipe,theatmosphereisusuallydividedintoasocalledboundarylayer(sometimesalsocalledthefrictionlayer)andthefreeatmosphere.Theatmosphericboundarylayer(upto1or1.5km)isinfluencedconsiderablybytheEarth’ssurfaceandbyeddy-viscosityforces.Atthesametime,wecanneglect,asafirstapproximation,theinfluenceofeddy-viscosityforcesinthefreeatmosphere.
Ofalltheaboveatmosphericlayers,onlythetroposphere(especiallyitsboundarylayer)ischaracterizedbyamarkedinstabilityoftheverticaldistributionofthemeteorologicalparameters.Itisinthislayerthatbothtemperatureinversionsandsuperadiabatictemperaturevariationswithheightareobserved.
TheEarth’satmosphereisamixtureofgasesandaerosols,thelatterbeingthenamegiventoasystemcomprisedofsmallliquidandsolidparticlesdistributedintheair.
Airisnotaspecificgas:
rather,itisamixtureofmanygases.Someofthem,suchasnitrogen,oxygen,argon,neon,andsoon,mayberegardedaspermanentatmosphericcomponentsthatremaininfixedproportionstothetotalgasvolume.Otherconstituentssuchaswatervapor,carbondioxide,andozonevaryinquantityfromplacetoplaceandformtimetotime.
Theprincipalsourcesofnitrogen,themostabundantconstituentofair,aredecayingfromagriculturaldebris,animalmatter,andvolcaniceruption.Ontheothersideoftheledger,nitrogenisremovedfromtheatmospherebybiologicalprocessesinvolvingplantsandsealife.
Toalesserextent,lightningandhightemperaturecombustionprocessesconvertnitrogengastonitrogencompoundsthatarewashedoutoftheatmospherebyrainorsnow.Thedestructionofnitrogenisintheatmospheresinbalancewithproduction.
Oxygen,agascrucialtolifeonEarth,hasanaverageresidencetimeintheatmosphereofabout3000years.Itisproducedbyvegetationthat,inthephotosyntheticgrowthprocess,takesupcarbondioxideandreleasesoxygen.Itisremovedfromtheatmospherebyhumansandanimals,whoserespiratorysystemsarejustthereverseofthoseoftheplantcommunities.Weinhaleoxygenandexhalecarbondioxide.
Oxygendissolvesinthelakes,riversandoceans,whereitservestomaintainmarineorganisms.Itisalsoconsumedintheprocessofdecayoforganicmatterandinchemicalreactionswithmanyothersubstances.Forexample,therustingofsteelinvolvesitsoxidation.
Fromthehumanpointofview,thescarce,highlyvariablegasesareofgreatimportance.Themassofwatervapor,thatis,H2Oinagaseousstate,intheatmosphereisrelativelysmallandisaddedtoandremovedfromtheatmosphererelativelyfast.Asaresult,theaverageresidencetimeofwatervaporisonly11days.Watervaporisthesourceofrainandsnow,withoutwhichwecouldnotsurvive.
Fromcommonexperiencesitiswellknownthatthewatervaporcontentofairvariesagreatdeal.Inadesertregiontheconcentrationofwatervaporcanbesolowastorepresentonlyatinyfractionoftheairvolume.Attheotherextreme,inhot,moistairnearsealevel,sayoveranequatorialocean,watervapormayaccountforasmuchasperhaps5percentoftheairvolume.
Therearelargevariationsofatmosphericwatervaporfromplacetoplaceandfromtimetotime,butthetotalquantityovertheentireEarthisvirtuallyconstant.Thesamecannotbesaidaboutcarbondioxide(co2).Theconcentrationofthissparsebutimportantgashasbeenincreasingforthelasthundredyearsorso.
Carbondioxideisaddedtotheatmospherebythedecayofplantmaterialandhumusinthesoil,andbytheburningoffossilfuels:
coal,oil,andgas.Theprincipalsinksofco2aretheoceansandplantlifethatusesco2inphotosynthesis.
Inthemiddle1980s,atmosphericchemistswerestilldebatingabouttheeffectsonatmosphericco2ofburning,harvestingandclearingofforests.Theoceanstakeuplargeamountsofco2,abouthalftheamountreleasedbyfossilfuelcombustion.Itisexpectedthatthisfractionwilldiminishwiththepassingdecadeswhereasthetotalmassofco2releasedwillincrease,atleastthroughtheearlypartofthenextcentury.
Duringthe1980satmosphericco2wasaccumulatingatarateofabout1partpermillion(ppm)ofairperyear,butitisexpectedtoincreasemorerapidlyindecadestocome.In1983itaveragedabout340ppmofair.
Ozone(o3),anotherimportant,highlyvariablegas,occursmostlyatupperaltitudes,butitisalsofoundinurbanlocalitieshavingagreatdealofindustryandautomotivetrafficandageneroussupplyofsunshine.IncitiessuchasLosAngeles,ozoneconcentrationmaybemorethan0.1ppminextremecases.Mostatmosphericozoneconcentrationsoftenexceed1.0ppmandmaybelargeas10ppm.
Theyvarygreatlywithlatitude,season,timeofday,andweatherpatterns.Thehigh-altitudeozonelayerismaintainedbyphotochemicalreactions.Theozonelayerisimportantbecause,byabsorbingUVradiationintheupperatmosphere,itreducestheamountreachingthesurfaceoftheEarth,exposuretoincreaseddosesofultravioletrayswouldcausemoreseveresunburnsandincreasetheriskofskincancers.
BiologistsindicatethatasubstantialincreaseinUVradiationcouldalsoaffectothercomponentsofthebiosphere.
Certaingages,iftheyexistinsufficientlyhighconcentrations,canbetoxictopeople,animalandplantlife.Forexample,whenozoneoccursinhighconcentrations,itistoxictobiologicalorganisms.Thisdoesnothappenoften,butinheavilypollutedlocalitiessuchasLosAngeles,ozonenearthegroundsometimesissufficientlyabundanttocauseleafdamagetocertainplantspecies.
Verylargequantitiesofpotentiallyhazardousgasesareintroducedintotheatmosphereasaresultofhumanactivities.Airpollutantsareemittedfromfurnaces,factories,refineries,andengines,particularlyautomobileengines.
Allthesethingsandotherslikethemburnfossilfuels:
coal,oil,gasoline,andkerosene.Intheprocesstheyemitgasesandsmokeparticlesthatmayspendagreatdealoftimeintheatmospherereactingwithothersubstancesandcausingtheformationoftoxiccompounds.
Themostwidespreadandpotentiallyhazardousgaseouspollutantsarecarbonmonoxide,sulfurdioxide,nitrogenoxide,andhydrocarbons.Thelastofthesecompoundscomesfromvaporizedgasolineandotherpet
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