Atmospheric（內(nèi)網(wǎng)） Lec.7:RadiationandClimate（2000.03-2004.05，單位：W Trenberth等1 r20(-)=r2sTe取S01367Wm-2，R0.3，可算出Te255K-18C。地–吸收率為As，對長波輻射的吸收率為AL。根441-4aAL+T4g1AL)1-R-s4aA=sTLgT4=gaT4=a

121- 2Tg=278.6K，Ta=247.7DDT=Q-DF)gDtCpQ:ΔFz=z+z全球地面輻射差額[(SS’)(1αLe0]，大氣輻射差額(QΔF)以前就凝結(jié)；對流層頂以下熱量難以通過湍流模式(RadiationConvcctionModeL簡稱RCM)CCM3(TheNCARCommunityModel)theCommunityAtmosphereModelRegCM2RadiativeRadiativeInThenetfluxofradiationintooroutofaAsaconsequenceofradiativeforcingtheremustbesomechangetothenonradiativeenergystatesofthesystem(e.g.,itstemperaturemaychange).RadiativeInAsystematicperturbationtotheclimatologicalvalueofthenetradiantfluxdensityatsomepointintheearth'sclimateForexample,thisperturbationmaybeduetoachangeinconcentrationoftheradiativelyactivegases,achangeinsolarradiationreachingtheearth,orchangesinsurfaceRadiativeInclimatescience,radiativeforcingorclimateforcing,isdefinedasthedifferenceofradiantenergy(sunlight)receivedbytheEarthandenergyradiatedbacktospace.Typically,radiativeforcing fiedatthetropopauseinunitsofwattspersquaremeteroftheEarth'ssurface.Apositiveforcing(moreingenergy)warmsthesystem,whilenegativeforcing(moreoutgoingenergy)coolsit.RadiativeRadiativeforcingsincesemi-directeffect?VerylowFromVerylow

RadiativeFromIPCCRadiativeFromIPCCClimateRadiativeforcingcanbeusedtoestimateasubsequentchangeinequilibriumsurfacetemperature(ΔTs)arisingfromthatradiativeforcingviatheequation:DTs=whereλistheclimatesensitivity,usuallywithunitsinK/(W/m2),andΔFistheradiativeAtypicalvalueofλis0.8K/(W/m2),whichgivesawarmingof3KfordoublingofCO2.全球增暖潛力(GlobleWarmingnGWP

0n0n

ttThevariousradiativemechanismsassociatedwithcloudeffectsthathavebeenidentifiedassignificantinrelationtoaerosols.(IPCC,2007)Directeffect:scattering/absorbingSemi-directaerosolabsorptionheatsatmosphericlayerwarmerair→lowerRH→less/nocloudIndirecteffect:modifyingcloud“brightness(first)effect”“l(fā)ifetime(second)effect”GlaciationeffectDirect

e.g.Blackcarbon,mineral

tospace(Cooling)e.g.Sulphates,nitrates,MostaerosolsbothabsorbandDifferentScatteringandabsorptionofsolarandterrestrialradiationcoolingatthetopoftheatmospherefromscatteringaerosolssuchassulfatewarmingatthetopoftheatmospherefromabsorbingaerosolssuchassoot t=e-t+w-b-e-t r

+t2rR

+t2r2R

F?=r+t2R+

=

1

rR+r2R

+r3R

=r+ s r<1;R 1- s

F?

t2R

=r+ s

1-rRsDDR= -=r t2Rps1-rRRssDDF=FDR=0p0 c2art2Rs1-rR-Rss輻射強(qiáng)迫(Radiative 2

t2R

-F

=-DF=-F1-A r

-R ss

1-rRs r=wb-e-t;t=e-t+w-b-e-t solarflux(W·m-Ac:fractionofthesurfacecoveredbycloudsTa:fractionaltransmittanceoftheatmosphereRs:albedooftheunderlyingEarthsurfaceω:single-scatteringalbedooftheβ:upscatterfractionoftheτ:aerosolopticalCoolingvs.F?=r+t2R+t2rR2+t2r2R3 -ΔRp>0:ΔRp<0:由ΔRp0ωcω>ωc:coolingω<ωc:heatingCoolingvs.τ~-=e-t+w-b-e-t1-t+w-b2spDR=rsp

t2R

wb

1-b

ss-ss1- 1-wbs?1-

2

2Rs

1 bwc=2Rs+b-Rs2Coolingvs.cw c2R+b1-R aerosoleffectson yamajorroleintheclimatesystem.AsmallchangeincloudpropertiescanstronglyaffectclimateThesemi-directAerosolsabsorbsolarEvaporationoftheAbsorbingaerosolsinandaroundacloud

AbsorbingaerosolsmayreducelowcloudThiswouldwarmtheclimateaslowcloudsscattersolarradiationbacktospace.Noconsensusonhowimportantthesemi-directeffectis!Firstindirectaerosoleffect(cloudalbedoforaconstantcloudwatercontent,moreaerosolsleadtomoreandsmallerclouddropletslargercrosssectionalareamorereflectionofsolarradiationSecondindirectaerosoleffect(cloudlifetimeeffect)themoreandsmallerclouddropletswillcollideasefficientlydecreasedrizzleformationincreasecloudlifetimemorereflectionofsolarradiationIndirectaerosoleffectFewLessreflectivecloud

NumerousaerosolsMorereflectivecloud(Coolerclimate)IndirectaerosoleffectEvidenceforthe1stindirectaerosoleffectinmarinestratusclouds

Pengetal.,Indirecteffect CloudsarelongerlivedandretainhigherliquidwatercontentEvidenceofthe2ndindirectPengPengetal.,Whyistheindirecteffectpoorlyunderstood?Indirectforcinguncertaintiesarisebecause:Aerosol-cloudin ctionstake ceatsmallerspatialscalesthanclimatemodelscanresolve,andmustbeparameterized.Aerosol-cloudin ctionsarecomplex;manyaspectsareunknownorpoorlyunderstood.Climatemodelsprovidelimitedinformationaboutclouds,andaerosols.Whyistheindirecteffectpoorlyunderstood?CentralproblemofindirectDeterminetherelationshipbetweenaerosol