中國(guó)地質(zhì)大學(xué)武漢環(huán)境化學(xué)03Atmosphericradiationandparticle課件

ChapterthreeClimate:RadiationBalanceAlbedo:ParticlesandClouds(星體)反照率1.Climate:RadiationBalanceWeatherandClimateFactorsaffectingtheearth’sclimateSolarirradiation:SolarconstantRadiationBudgetAlbedoTheincomingsolarenergyperunitareaattheearth’ssurfaceSpectraldistributionofsolarandterrestrialradiationBalancingincomingandoutgoingenergyfortheEarth-AtmospheresystemWeatherandClimateWeatheristheconditionoftheatmosphereintermsoftemperature,humidity,windsandprecipitation.Climateisdefinedastheaverageweatherovervarioustimeperiodsrangingfromafewweekstodecadestogeologicaltimescales.

Whetherandclimateareultimatelydeterminedbylocation,topography,andtheexchangeofradiantenergybetweentheSun,Earth,andspace.Solarirradiation:SolarconstantSolarconstant:TheamountofsolarenergyreceivedperunitofareaoutsidetheEarth’satmosphere,normaltothedirectionofpropagationofthelight.RadiationBudgetTheEarth'sclimatesystemconstantlytriestomaintainabalancebetweentheenergyfromtheSunthatisabsorbedbytheEarth,andtheenergythatgoesfromEarthbackouttospace.WerefertothisprocessasEarth's"radiationbudget."ThisradiationbudgetallowstheEarthtomaintainthemoderatetemperaturerangeessentialforlifeasweknowit.ThecomponentsoftheEarthsystemthatareimportanttotheradiationbudgetaretheplanet'ssurface,atmosphere,andclouds.RadiationBudgetattheTopoftheAtmosphereWhatcontributestotheglobalalbedo?Cloudsaccountfortwo-thirds(67%)oftheglobalalbedoBackscatteringfromgaseousmoleculesandparticlesintheair:20%Earth’ssurface:13%AlbedoforvarioustypesofsurfaceSurfacealbedoClouds(averageoveralltypes)0.35-0.40Snow0.60-0.80Ocean0.06-0.20Deserts0.25-0.40Agriculturalland0.10-0.20Forest0.10-0.20Theincomingsolarenergyperunitareaattheearth’ssurfaceSolarenergystrikesearthat1370watts/m2toadiskareapr2(r:earthradius).Earthradiatesfromitsentiresurface,whichis4pr2.TheenergyEarthreceivesatthetopoftheatmosphereistherefore:So/4.Afraction(a)ofsolarenergyisreflectedbacktothespaceTheincomingsolarenergyperunitareaattheEarth’ssurface:HowtheoutgoingenergyoftheearthrelateswiththeEarth’stemperature?(Continued)Stefan-BoltzmanlawE:radiatedenergyperunittimeperunitareaTe:BlackbodytemperatureSpectraldistributionofsolarandterrestrialradiationTheCorrespondingblackbodytemperaturefortheEarthandtheSunlmaxTe(K)Sun483nm6,000KEarth10,000nm288kApproximatetheearthsurfacetemperatureWhytheblackbodytemperatureoftheearth-atmospheresystemseenfromthespaceis33kcolderthantheaveragetemperatureattheearthsurface?Earth-Atmospheresystem:255kEarthsurfaceaveragetemperature:288kAnswer:Greenhouseeffect.

TheatmospheretrapsmuchoftheheatemanatingfromEarth’ssurfaceandradiatesitback,raisingthesurfacetemperature.2.Albedo:ParticlesandCloudsCloudalbedoforcing:CoolingCloudGreenhouseForcing:WarmingOveralleffectofallcloudsAerosol:definitionAerosolsourcesAerosolRadiativeForcing:directeffectVolcanoesandclimatechangeSulfateaerosolformationfromvolcanoeruptionsSulfateformationfrombiogenicgasesAerosolEffectsonClimateCloudalbedoforcing:CoolingTheshortwaveraysfromtheSunarescatteredinacloud;manyoftheraysreturntospace.Theresulting"cloudalbedoforcing”,takenbyitself,tendstocauseacoolingoftheEarth.OveralleffectofallcloudsCloudalbedoforcingcoolingCloudgreenhouseforcingwarmingTheoveralleffectofallcloudstogetheristhattheEarth'ssurfaceiscoolerthanitwouldbeiftheatmospherehadnocloudsThedominatefactorintheglobalalbedoisclouds.Aerosol:DefinitionAerosolisasuspensionofsolidorliquidparticlesinagas.Atmosphericaerosolsconsistofsmallparticlesofliquidandsolidmaterialsuspendedintheair.Bioaerosol:Anaerosolofbiologicalorigin.(Examples:viruses,bacteria,fungi,spores,andpollens.)Aerosolsizesareusuallymeasuredintheunitofmicrometer(mm)1mm=10–6m1mm=104angstrom(?)TypicalParticleDiameters(mm)Photochemicalaerosols0.01-1Tobaccosmoke0.25Coalflyash1-50Flourdust15-20Pollens15-70Humanhair:~25-100mmAerosolsourcesAerosolsourcesWindblowndustfromDesertSulfateaerosolfromvolcanoeruption,fuelcombustionandmicrobialactivities.SeasaltaerosolfromseasprayandbubbleburstingSootfromfuelcombustionSecondaryorganicaerosolfromvolatileorganiccompoundsAerosolradiativeforcing:indirecteffectAnincreaseinthenumberofatmosphericparticleswouldincreasethenumberofcloudcondensationnuclei,thereforemorecloudcoverandhigheralbedoShiptrackingphenomenonVolcanoesandclimatechangeLargevolcanoeruptionsprovidedramaticevidenceoftheabilityofaerosolstoaffectglobalclimate.Mt.Pinatuboeruptionmade1992thecoolestyearsince1986Redline:modeledtemperaturechangesBlueline:temperaturechangesobservedfrommeteorologicalgroundstations1816-theyearwithoutasummerIn1815,TamborainIndonesiaexplodedandthevolcanodustblanketedtheNorthernHemisphere.Thefollowingyear,1816,dailyminimumtemperatureswereabnormallylowinthenorthernhemispherefromlatespringtoearlyautumn.Faminewaswidespreadbecauseofcropfailures.Anestimated82,000werekilledindirectlybytheeruptionbystarvation,disease,andhunger.SulfateaerosolformationfromvolcanoeruptionsLargeamountofSO2isinjectedintotheatmospherefromtheforceofthevolcanoeruption.SO2canbeconvertedtosulfateingasandaqueousphase.Ingas-phaseSO2+.OH+MHOSO2.+MHOSO2.+O2HO2.+SO3SO3+H2O+MH2SO4+MSulfateaerosolformationfromvolcanoeruptions(Continued)Inaqueousphase,dissolvedSO2isoxidizedtosulfatebyO3 (dominantpathwaywhenpH>5)H2O2 (dominantpathwaywhenpH<5)organicperoxidesO2catalyzedbyironandmanganeseTheoxidationofSO2(aq)byH2O2proceedsasfollows:HSO3-+H2O2

SO2OOH-+H2OSO2OOH-+H+H2SO4SulfateformationfrombiogenicgasesDimethylsulfide(DMS):CH3SCH3MarineoriginProducedinplanktonbytheenzymaticcleavageofdimethylsulfonopropionate,acompoundthathelpplanktonachieveosmoticbalanceinthesaltyoceanwa