Concentrationsrrqqq.com

AFGt-TR-79-O214ETIVIROT{TEiITALRESEARCHPAPERS,NO.
6i'6ModelsfortheAerosolsoftheLowerAtmosphereandtheEffectsofHumidityVariationsonTheirOpticalPropertiesERICP.
SHETTTEROBERTW.
FENN20September1979Approrrdforpublicrol.
.
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AF9,ilASSACt{UsETTs0t731AIRFORCESYSTEMSCOMMAND,USAFThisreporthasbeenreviewedbytheESDInfornationOffice(OI)andisreleasabletotheNationalTechnicalInforznationService(NTIS).
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lEREFORTDOCUhENTATIONPAGEAFGL.
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)MODELSFORTI{E.
A-EROSOLSOFTHELOWERATMoSpHEREANDrunerFbcis-oiHUMIDITyvARTATIoNSowrnninOPTICALPROPERTIESEricP.
ShettleRobertW.
FennERPNo.
66AirForce.
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glophysicaLaboratory(Op)HanscomAFBMassachusetts013120September199UnclassifiedApprovedforpublicrelease;distributionunlimited.
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otsTRtBuTtolsrrreAtmosphericopticalpropertiesLrghtscatteringInfraredAttenuationAerosblsRadiativetransferAlshAC:(Cq.
In6-n@puteatorwaveteristrrsuetweenb.
la;.
i'4d;';:if"1.
;;:,TEJB,'filiJ,"1#Aerosolmodelshavebeendeveloped-fortheloweratmosphere.
Thesemodelsarerepresentativeofconaiiiols_foundin;;;;i,l"6"rr,andmaritimei,i:Ti:i::;ljr^",".
1"^T.
c-"^1.
i"t[e_leroso]n;;o;;;iiirr*"""rationsintherera-tivehumiditvaredisculeed.
roaescriuetheaer.
os","p,ril-iTi$:rfr:3"rJ:iextremeofr00percent.
rerativehumidity,severalfognio;ersarepresented.
Foreachmodel-thecoefficientsir.
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"0absorption,the:lrij.
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The-optical--;;;;i;";FA;;;modelsarediscueseaanasomecomParigoneoftbemodeli"itti"tp""imentalmeaaurementgarepresented'Unclassified;ECUR|tyCLASSTFICAlO}|OFrHlsPAGE(11|.
^Dd.
Edtc.
.
ct)Prefocewewourdliketothankseverarindividuarswhoherpedwiththisreport,inparticu!
.
ar;FredVolzforhisadviceontheaerosolrefractiveindicesandhisgeneralcommentsontheaerosolmodels,FrankGibsonforhisworkindevel,opingtheFogModels,andBarrysiegelforhisassistancewiththecomputerprogramming.
1.
INTRODUCTION2.
MODELSFORTI{EPHYSICALPROPERTIESOFTHEAEROSOLS2.
LModelSizeDistribution2.
2EffectsofHumidityvariationsonAerosolproperties2.
3RuralAerosolModel2.
4UrbanAerosolModel2.
5MaritimeAerosolModel2.
6TroposphericModel2.
7FogModels3.
AEROSOLOPTICALPROPERTIES3.
IMieScatteringCalculations3.
2AerosolModelAttenuatlon3.
3FogModelAttenuation3.
4TablesofAerosolAttenuation4.
THEUSEOFTHEAEROSOLMODELS4.
IBoundaryLayerModels4.
2TroposphericAerosolModel4.
3FogModelsREFERENCESContenls1ltzt2t4161926303335353646498686878789lllustrotions1.
RefractiveIndexofMarineAerosol,Water,andSeaSaIt2.
RefrlctiveIndexfortheDryRuralandurbanAeroeolcomponents3.
Aerosol.
NumberDietributionfortheRuralModelatDifferentRelativetlumiditieewithrotalparticleconcentrationsFixedat15,000cm-34.
cumulativeNumberDensityfortheRuralAerosolModelatDifferentRelativeHumiditieewithrotalparticleconeentrationgF"ixedat15,000cm-J5.
VolurneDistributionfortheRuralAerosolModelatDifferentRelativeHumiditieswiththeTotalparticleconcentrationeFiredat15,000cm-36.
AerosolNurnberDistributionfortheMaritimeModetatDifferentRelativeHumiditie-swiththeTotalparticleconcentrationsFixedat4000cm-r7.
cumulativeNumbsDenaityfortheMaritimeAerosolModelatDifferentRelativeHumiditiesWiththeTgtalParticleConcentrationsFixedat4000cm-r8.
volumeDistributionfortheMaritimeAerosolModelatDifferentRelativeHumiditieswiththeTotalparticleconcentrationsFixedat4000cm-39.
AerosolNumberDistributionfortheTroposphericModelatDifferentRelativeHumiditieswithTotalparticleconcentrationsFixedat10,000em-33110.
cumulativeNumberDensityfortheTroposphericAerosolModelatDifferentRelat-iveHumiditiesWithToialParticleConcentrationsFixedat10,000cm-r3211.
volumeDistributionfortheTroposphericAerosolModelatDifferentRelativeHumiditiesWiththetotilParticleConcentrationsFixed.
at10,000cm-r12.
NumberDistributionfortheDifferentFogModets13.
cumulativeNumberDietributionfortheDifferentFogModets14.
VolumeDistributionfortheDiffer.
entFogModels15.
AttenuationcoefficientsvswavelengthfortheRuralAeroeolsat50PercentRelatlveHumidity16.
AttenuationcoefficientsvswavelengthfortheRuralAerosolModelsatgbpercentRelativeHuiriditv17.
Extinctioncoefficientsvswavel^engthfortheRuralAerosolModelforDifferentRelativeHumiditieJandconstantNumoero""sitvorPar-ticles3lB.
AttenuationcoefficientsvswavelengthfortheurbanAeroeolsat50PercentRelativeHumidity19.
AttenuationcoefficientsvswavelengthfortheurbanAerosolsat95PercentRelativeHumiditv20.
ExtinctioncoefficientsvswavelengthfortheurbanAerosolModelforDifferentlrelativeHurhiditieJandconstantNumberoensity-ofParticles392L.
Attenuati.
oncoefficientsvswaverengthfortheMaritimeat50percentRelativeHumidity:ia9.
*,t717202l2l272728323434353633839AerosolModel40lllustrotions22.
AttenuationcoefficientsvswavelengthfortheMaritimeAerosolModelat95PercentRelativettumidity23.
ExtinctioncoefficientsvswavelengthfortheMaritimeAerosolModelforDifferentRelativeHumiditiesandconstantNumberDensityofParticles24.
AttenuationcoefficientsvswavelengthfortheTropoephericAerosolModelatb0percentRelJtiveHumidity25.
AttenuationcoefficientsvswavelengthfortheTroposphericAerosolModelatg5percentRelaiiveHumidity26.
ExtinctioncoefficientsvswavelengthfortheTroposphericAerosolModelforDifferentRelitiveHumiditieiandconstantNumberDensityofparticles27.
AttenuationCoefficientsvsWavelength;HeavyAdvectionFog,Model128.
Attenuationcoefficientsvswavelength;LighttoModerateAdvectionFog,Model229.
AttenuationCoefficientsvsWavelength;HeavyRadiationFog,Model330.
AttenuationCoefficientsvsWavelength;LighttoModerateRadiationFog,Model431.
ExtinctioncoefficientsvswavelengthfortheDifferentFogModels404l4142424647474848Tobles1.
characteristicsofAerosolModelsoftheLowerAtmosphere142.
ModeRadiifortheAerosolModelsasaFunctionofRelativeHumidityL43.
RefractiveIndexfortheDifferentAerosolComponentslg4.
RefractiveIndexoftheRuralModelasaFunctionofRelativeHumidityandWavelength,(a)SmallRuralAerosols,(b)LargeRuralAerosol:sZz5.
RefractiveIndexoftheUrbanModelasaFunctionofRelativeHumiditvandWavelength,(a)SmallUrbanAerosols,(b)LargeUrbanAerosois246.
RefractiveIndexoftheoceanicModelasaI'unctionofRelativeHumidityandWavelength7.
SizeDistributionParametersoftheFogModels8.
TotalNumberDensityfortheRuralAerosolModelasaFunctionofRelativeHumidityandMeteorologicalRange9.
TotalNumberDensityfortheurbanAerosolModelasaFunctionofRelativeHumidityandMeteorologicalRange10.
TotalNumberDensityfortheMaritimeAerosolModelasaFunctionofRelativeHumidityandMeteorologicalRange2933444445Tobls:11.
TotalNumberDensityfortlreTroposphericAerosolModelaeaFunctionofRelatlveHumidityandMeteorologicalRangeL2.
AttenuationCoefficienta,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=0%RuralModel13.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=5O%RuralModel14.
AttenuationCoefficients,SingleScatterAlbedo,andAeymmetryParameterforRelativeHumidity=70%RuralModel15.
AttenuationCoefftcients,SlnglScatterAlbedo,andAeymmetryParameterforRelativeHumidity=BWoRuralModel16.
AttenuationCoefficiente,Sin$lScatterAlbedo,andAsymmetryParameterforRelativeHumidity=9O1oFuralModel17.
AttenuationCoefficiente,SingleScatterAlbedo,andAsymmetryParameterforRelativellumidity=95%RuralModel18.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=98%RuralModel19.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=99%RuralModel20.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=0%UrbanModel21.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumtdity=50ToUrbanModel22.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=701oUrbanModel23.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=8010UrbanModel24.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=9O%UrbanModel25.
Attenuati.
onCoefficients,SlngleScatterAlbedoiandAsymmetryParameterforRelativeHumidity=9510UrbanModel26.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=98%UrbanModel27.
AttenuationCoefflcients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=99ToUrbanModel28.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=0%MaritimeModel29.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=5O%MaritimeModel30.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=7Os/eMaritimeModel31.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=801oMaritimeModel32.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelattveHumidlty=9A%MaritimeModel45505152535455565758596061626364656667686970Tobles33.
AttenuationCggftigign!
:,S_Tgl9ScatterAtbedo,andAsymmetryParameterforRelativettumidity=95ToUaritimeModel34.
Attenuationc:lfi:1:llp:1r-"St9.
scatterAlbedo,andAsymmetryparameterforRelativeHumldity_gB%Mariiim;Moiel35.
Attenuationc::l-fi:l:ry:,lrler:ScatterAtbedo,andAsymmetryParameterforRelativenumiaity=gg%MaritimeModel36.
AttenuationC::l-fi:l:lF,S_t_r,CtgScatterAlbedo,andAsymmetryParameterforRelativeHu-midity=0%Tropospf,L"i"Model37.
AttenuationCggffilign!
:,Si"elgScatterAlbedo,andAsymmetryParameterforRelativettumidity=ieloTroposphericModel38.
AttenuationCggtfigigll:,S-.
-"g19-scatterAtbedo,andAsymmetryParameterforRelativeHumidity=7O%TroposphericModel39.
Attenuationc::l-f*l:lt:,S-.
_relg.
scatterAlbedo,andAsymmetryParameterforRelativeHumiaity=gO%TroposphericModel40.
AttenuationCo^gffigign!
:,S-r_"g19ScatterAlbedo,andAsymmetryParameterforRelativettumlaity=gO%TroposphericModel41.
AttenuationCoefficient:,S_r_"g19.
ScatterAlbedo,andAsymmetryParameterforRelativeHumldity=95%TroposphericModel42.
Attenuationcoefficient:,s-tlgl:-scatterArbedo,andAsymmetryParameterforRelativeHumidity=ggToTroposphericModel43.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRelativeHumidity=gg%TroposphericModel44.
AttenuationCo.
effi,gienjs,Single-scatterAlbedo,andAsymmetryParameterfortheAdvectionFogIModel45.
AttenuationCo"1f_fi.
9ien^{,Aipt"jcatterAlbedo,andAsymmetryParameterfortheAdvectidnFog2Model.
46.
AttenuationCq9ffi5ie,1ts,SingleScatterAlbedo,andAsyrnmetryParameterforRadiationFogIModel47.
AttenuationCoefficients,SingleScatterAlbedo,andAsymmetryParameterforRadiationFog2Model7l7273747576777879808182838485ModelsfortheAerosolsoftheLowerAtmosphereondtheEffectsofHumidityVoriotionsonTheirOpticolPropertiesI.
INTRODUCTIONPropagationofelectromagneticradiationatoptical/infraredfrequenciesthroughtheatmosphereisaffectedbyabsorptionandscatteringbyairmoleculesandbvparticulatematter(haze,dust,fog,andclouddroplets)suspendedintheair.
Scatteringandabsorptionbyhazeparticlesoraerosolsbecomesthedominantfactorintheboundarylayerneartheearth'seurface,especiallyunderlowvisibilitycon-ditions.
Atmosphericaerosolparticlesintheatmospherevarygreatlyintheirconcen-tration,size'andcomposition,andconsequentlyintheireffectsonopticalandIRradiation.
Therearemanyscientificandtechnicalreasonswhyitisnecessarytodevelopmodelsforatmosphericaerosols.
Theyareneededtomakeestimatesofthetrans-mittance,ofangularlightscatteringdistribution,ofcontrastreduction,skyradiance,orotheratmosphericopticalpropertiesoreffects.
Modelsfortheoplic_alpropertiesofaerosolshavebeendevelopedpreviouslyatAFGLandelsewhu"".
t-*Forthelowerlayerneartheearth'ssurface,thesemodelsdefineanaveragecontinentaltypeaerosolwhoseconcentrationcanbescaledaccordingtosurfacevisibility.
GecffiA-Iorpublication20Septembert99)Pu9to.
thelargenumberofreferencescitedinthisreport,theywillnotbefootnoted.
SeeReferences,pagesggthrough94.
11Theaerosolpropertieeinthesemodelswerebasedonexperimentalmeaeure-mentgthatweremadeduringandpriortothemid-1960's.
Atthattimetherewassufficientexperimentaldataavailabletodefineanaverageaerosolmodelwithsomedifferenthazeconcentrationsinthelowertroposphere(uptoafewkmaltitude)withexponentialverticaldecreaseinparticleconcentration.
Duringthepastdecade,inthiscountryandelsewhere,extensiveadditionalmeasurementsfromgroundaswellasairborneplatformshavebeenmadeofaerosolconcentrations,theirsizedistribution,andopticalproperties,towarrantthedevelopmentofupdatedaerosolmodelsthatalsodescribesomeofthetemporalandspatialvariationsinatmosphericaerogoldistributionsandproperties.
Therearenowsufficierrtexperimentaldatatodevelopmodelsforseveraldi.
fferentt5ryesoftroposphericaerosols,includingthedependenceoftheaerosolpropertiesonrela-tivehumidity.
SuchupdatedmodelshavebeendevelopedbyShettleandFennSaridToonandaPoIIack,"exceptbothofthesesetsofmodelsneglecttheeffectsofrelativehumidity.
Thepresentreportdescribesaerosolmodelsfortheloweratmosphereandtheiropticalpropertiesincludingadiscussionofhowtheaerosolpropertieschangeasafunctionofrelativehumidity.
Theopticalpropertiesofthemodelsaregivenforanumberofwavelengthsbetween0.
2and40pm,andforseveraldifferentrelativehumiditiesrangingfrom0to99percent.
Inadditionfourfogmodelsaregivenforttredroplet-condensationphase.
Themodelsoftheatmosphericaerosolsandtheiropticalpropertiespresentedbelowarebasedonareviewoftheavailabledataonthenatureoftheaerosols,theirsizes,theirdistribution,andvariability.
However,itmustbeemphasizedthatthesemodelsrepresentonlyasimple,generalizedversionoftypicalconditions.
Itisnotpracticaltoincludeallthedetailsofnaturalaerosoldistributionsnorareexistingexperimentaldatasufficienttodescribethefrequeneyofoccurrenceofthedifferentconditions.
WhiletAeseaeroeolmodelsweredevelopedtobeasrepresenta-tiveaspossibleofdifferentatmosphericconditions,thefollowingpointshouldbekeptinmindwhenusinganysuchmodel:Giventhenaturalvariabilityoftheatmosphericaerosolsalmostanyaerosolmodelissupportedbysomemeasurementsandnomodel(orsetofmodels)willbeconsistentwithallmeasurements.
2,MODEI,SFORTHEPHYSICALPROPERTIESOFTHEAEROSOLS2.
LModelSizeDistributironThesizedistributionsforthedifferentaerosolmodelsarerepresentedbyoneorthesumoftwolog-normaldistributions:L22n(r)=#,p,[-""'';it""1.
(1))exPwhereN(r)isthecumulativenumberdensityofparticlesofradiusr;oisthestandarddeviation;"i,Niarethemoderadiusandthenumberdensitywithrr.
Thisformofdistributionfunctionrepresentsthemultimodalnatureoftheatmos-phericaerosolsthathasbeendiscussedinvariousstudies.
l0-14whileHarrisandMcCormickl5h.
rr.
suggestedusingthesumoffourlog-normaldistributionsandDavies16hasusedthesumofasmanyassevenlog-normaldistributionstofitameaeuredaerosolsizedistribution,WhitbyandCantreUlThaveshownthattwomodesaregenerallyadeguatetocharacterLzethegrossfeaturesofmostaerosoldistributions.
WhileathirdcomponentisoftennecessarytorepresenttheAitkennucleiespeciallynearsourcesofcombustionparticulates,theireffectontheopticalpropertiesissmallandwillbeneglected.
Therearemeasurements-showingthecompositionoftheatmo-sphericparticu-Iatesdependingontheirsize,18,19andusingabimodalsizedistributionoffersthepossibilityoftreatingthecompositionoftheindividualmodesseparately.
However,thereis,ingeneral,insufficientexperimentaldatatouniquelydefinedifferentrefractiveindexmodelsforthedifferentsizeranges,alongwithdi.
fferingdependenceonrelativehumidity.
Forthemaritimeconditions,thereis.
rridence20showingthattheIargepar_ticlesarealmostexclusivelyofoceanicoriginandthesmallerparticlesarepre-dominantlyofthesamecompositionasthecontinentalaerosolssothatwedonordifferentiatebetweenthetwosizerangesintermsoftheircompoeition.
Fourdifferentaerosolmodelsfortheatmosphericboundarylayerneartheearth'ssurfacehavebeendeveloped.
Theydifferinparticlesizedistributionandparticlerefractiveindex.
TableIliststheparametersdefiningthesizedistribu-tionsinaccordancewithEq.
(1)forthesemodels.
ThechoicesofNinTable1arenormalizedtocorrespondtoIparticle/cm3.
Theactualsizedistributionscanbere-normalizedtogivethecorrectextinctioncoefficientsforthealtitudeandforthevisibilitybeingused.
Thecontinentalandoceaniccomponentsofthemaritimemodelcanbeusedinvariousproportionsdependingontheprevailingwinds-particularlyincoastalregions.
ThebasisforthecharacterizationofeachoftheaerosolmodelsisdiscussedinSections2.
3through2.
6.
Followingtheusualconvention,togisthelogarithmtothebasel0andInisthelogarithmtothebasee.
13Tablet.
CharacteristicsoftheAerrosolModelsoftheLowerAtmoephereAerosolModelSizeDistributionTypeRURALURBANMARITIMEContinentalOriginOceanicOriginTROPOSPHERICN.
Ir.
I+o.
IMixtureofWater-SolubleandDust-Li.
keAerosolsRuralAerosolMixturewithSoot-LikeAerosolsRuralAerosolMixtureSeaSaltSolutioninWaterRuralAerosolMixture0.
9998750.
0001250.
9998750.
0001251.
1.
1.
0.
030.
50.
030.
50.
030.
30.
030.
350.
40.
350.
40.
350.
40.
35Thesemoderadiicorrespondtomoderatehumidities(0to80%);valuesofr.
asfunctionofhumidityaregiveninTable2.
ITable2.
ModeRadiifortheAerosolModelsasaFunctionofRelativeHumiditv2.
2EffecteofHumidityVariationeonAerodPmpertierAstherelativehumidityincreases,watervaporcondensesoutoftheatmos-phereontotheparticulatessuspendedintheatmosphere.
Thiscondensedwaterincreasesthesizeoftheaerosolsandchangestheircompositionandtheireffectiverefractiveindex.
Theresultingeffectoftheaerosolsontheabsorptionandscatter-ingoflightwillcorrespondinglybemodified.
Therehavebeenanumberofstudiesofthechangeofaerosolpropertiesasafunctionofrelativehumidity.
2L-28Thnemostcomprehensiveofthese,especiallyintermsoftheresultingeffectsontheaerosolopticalpropertiesistheworkofHdnel.
26-28RelativeHumidityTroposphericRuralMaritimeUrban'1"1"2tl,2QToSoTu70%8o1oso%gSoh981o99To0:0200o.
o27480.
02846o.
032740.
038840.
042380.
047510.
052150.
02700o.
o27480.
02846o.
032740.
038840.
042380.
047510.
052150.
43000.
430.
45710.
5470.
64620.
7078o.
97281.
17550.
16000.
17110.
20410.
31800.
38030.
46060.
60240.
75050.
025000.
025630.
029r10.
035140.
04180.
049040.
059960.
068470.
40000.
4113o.
47770.
58050.
70610.
86341.
16911.
4858t4Thechangeintheparticulatesizeisrelatedtotherelativehumidityby(followingHlnel'snotation)l'm(a)lr/sr(a)=rlt*o.
**|woL'moJwhereroisthedryparticleradius,pistheparticledensityrelativetothatofwater,mur(a.
,rr)isthemassofcondensedwater,moisthedryparticlemass,anda*isthewateractivitywhichisessentiallytherelativehumidityf,correctedforcurvatureoftheparticlesurface.
/-*u\twl"r"=r'"*PtE=!
,r,\w/wherec,=surfacetensiononthewetparticlesurface,V*=sPecificvolumeofwater,R*=specificgasconstantforwater,T=absolutetemperature(oK).
Forroomtemperature(T=298'K),ZoVn,+=0.
001056[micron](Hdnel,28paget2O).
Typicalatmospherictemperaturesareasmuchas20percentlowerbut,forparticleradiir>0.
01!
,m,thisleadstoerylorsoflessthan2percentincurvature(2)(3)effectsoEq.
(3)canberewrittenas.
.
,o=r.
exp(*ru_+),whererisinpmandwherethedependenceofronawhasbeenmadeexplicit.
Thereareanumberofstudiesonchangeinsizeormassofaerosolparticlesasafunctionofrelativehumidityforvariouselectrolytes2l'25andnaturalatmos-phericpatticulates.
11'12'15'17'18'19'22'23'26'28'29,30Hi.
r.
l28(inhisTableIV)hastabulatedhisandothermeasurementsof+,0"a.
vforvarioustypesoftov(4',15naturalaerceols.
However,evenwiththisdataontherelativemasgofcondensedwaterforuseinEq.
(2),itisnotpoesibletocombineEq.
(2)and(4)intoanexactanalyticexpressiongivingaerosolradius,r,asanexplicitfunctionofrelativehumidity,becausea.
,,appearsonbothsidesofEq.
(a).
Variousapproximationshavebeendeveloped.
"2''28'3LHowever,thesetendtobreakdownforsmallparticlesizesandhighhumiditiee.
Toavoidthelimitationsoftheseapproximations,Eq.
(2)and(4)wereusedalternatelyinaniterativemanneruntiltheyconverged(typically5or6iterations)startingwitha*rfontherightsideofEq.
(2).
Starti;Uwithr=roinE9.
(4)leadstothesameresult.
TointerpolatebetweenH5nel's-"datafordifferentwaterii+lactivities,a'andd''',itwasasgumedthat#+,=(s')"n=.
*+(no-n",)[r]J]'(5)OncethewetaerosolparticlesizeisfoundfromEq.
(2)and(4),theeffectivecom-plexrefractiveindex,n,issimplythevolumeweightedaverageoftherefractiveindexesofthedryaerosolsubstance,no,andwater,nw.
Eguivalently,thiscanbewrittenas(6)Fortherefractiveindexofwater,thesurveyofHaleandQuemy32*.
sused.
WhiletherearesomeminordifferencesbetweentheopticalconstantsinHaleandQuerry'ssurveyandthemorerecentmeaguremer,t"33'34th.
""differencesarecomparablewiththeexperimentalemorsandaresmallcomparedwiththeotheruncertaintiesinthemodelparameters.
TheserefractiveindexdataareshowninFigure1.
2.
3RuralAemsolllodclThe"RuralModelttisintendedtorepresenttheaerosolunderconditionswhereitisnotdirectlyinfluencedbyurbanand/orindustrialaerogolsources.
Theruralaerosolsareassumedtobecomposedofamixtureof0percentofwatersolublesubstance(ammoniumandcalciumsulfateandalsoorganiccompounds)and30per-centdust-likeaerosols.
Therefractiveindexforthesecomponentsbasedonthemeasurementsofvolr35'36is"ho*ninFigure2andtabulatedinTable3.
Theserefractiveindexdataweightedbythemixingratioofthetwocomponentsarecon-sistentwithotherdirectmeasuremerrt",3'38".
dwithvaluesinferredfrominsitumeasurements.
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WAVELENOTHFigureRefractiveIndexofOceanicAerosol,Water,andSeaSaItFigure2.
RefractiveIndexfortheDryRuralandUrbanAerosolComponentsto(nlerurr)l7-WATERSOLUBLES(VOLZ}--.
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