atmospheric and solar radiation大气和太阳辐射

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1、Chapter11FundamentalsofThermalRadiationAtmosphericandSolarRadiation11-50CThesolarconstantrepresentstherateatwhichsolarenergyisincidentonasurfacenormaltosun'sraysattheouteredgeoftheatmospherewhentheearthisatitsmeandistancefromthesun.Itvalueis.Thesolarconstantisusedtoestimatetheeffectivesurfacetempe

2、ratureofthesunfromtherequirementthatSUNEarthLr(4pL2)Gs4pr2(sTsun4)whereListhemeandistancebetweenthesunandtheearthandristheradiusofthesun.Ifthedistancebetweentheearthandthesundoubled,thevalueofdropstoone-fourthsince11-51CTheamountofsolarradiationincidentonearthwilldecreasebyafactorof(orto1.5%ofwhat

3、itwas).Also,thefractionofradiationinthevisiblerangewouldbemuchsmaller.11-52CAirmoleculesscatterbluelightmuchmorethantheydoredlight.Thismolecularscatteringinalldirectionsiswhatgivestheskyitsbluishcolor.Atsunset,thelighttravelsthroughathickerlayerofatmosphere,whichremovesmuchofthebluefromthenaturall

4、ight,lettingthereddominate.11-53CThereasonfordifferentseasonsisthetiltoftheearthwhichcausesthesolarradiationtotravelthroughalongerpathintheatmosphereinwinter,andashorterpathinsummer.Therefore,thesolarradiationisattenuatedmuchmorestronglyinwinter.11-54CThegasmoleculesandthesuspendedparticlesintheat

5、mosphereemitradiationaswellasabsorbingit.Althoughthisemissionisfarfromresemblingthedistributionofradiationfromablackbody,itisfoundconvenientinradiationcalculationstotreattheatmosphereasablackbodyatsomelowerfictitioustemperaturethatemitsanequivalentamountofradiationenergy.Thisfictitioustemperaturei

6、scalledtheeffectiveskytemperature.11-55CThereisheatlossfrombothsidesofthebridge(topandbottomsurfacesofthebridge)whichreducestemperatureofthebridgesurfacetoverylowvalues.Therelativelywarmearthunderahighwaysupplyheattothesurfacecontinuously,makingthewateronitlesslikelytofreeze.11-41Chapter11Fundamen

7、talsofThermalRadiation11-56CDuetoitsnearlyhorizontalorientation,windshieldexchangesheatwiththeskythatisatverylowtemperature.Sidewindowsontheotherhandexchangeheatwithsurroundingsurfacesthatareatrelativelyhightempe