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Modeling rotational Raman scattering in the Earths atmosphereRutger van DeelenJochen Landgraf Otto HasekampIlse Aben
September 13, 2006, KNMI
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Three questionsMultiple scattering. Multiple Raman scattering?
Polarization?
Dependence on input solar spectrum?
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Measured GOME spectrasolar irradiance spectrumEarth radiance spectrum
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The GOME reflectivity spectrum
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The GOME reflectivity spectrumRaman
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Rotational Raman scatteringCabannes96 % elasticRaman4 % inelasticAIR (N2, O2)Raman
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Filling-in
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Filling-in
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Doubling-addingapproachPerturbation theory approachw Pw Pw Pw PAw Pmultiple orders of Raman scattering,comes out naturally,scalarone order of Raman scattering,fast,vector
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Rayleighwray(l)tray(l) single scattering albedooptical thicknessphasefunctionPrayQ
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RayleighCabannes + Ramanwray(l)w(l,l)tray(l) = tcab(l) + S tram(l,l)
tray(l) single scattering albedooptical thicknessphasefunctioninelasticelastictotalPrayPramPcabwcab(l)wram(l,l)QlQinelastic
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Doubling-adding approachRT
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Doubling-adding approachRTRabTabab
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Perturbation theory approach: based on the Greens functiona(z,l,W)b(z,l,W)
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Perturbation theory approach: based on the Greens functionarrow includes multiple scattering!a(z,l,W)b(z,l,W)G = G(z,l,W;z,l,W)Gdescribes how the atmosphere responds to light
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Perturbation theory approach: based on the Greens functionabGG = Gray Gray [ D Gray ] + Gray [ D Gray ]2 Gray [ D Gray ]3 + Dyson seriessource and target are fixedarrow includes multiple scattering!
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Perturbation theory approach: expansion of the Greens functionabGrayRayleigh
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Perturbation theory approach: expansion of the Greens functionabGrayabGrayGrayD-Rayleigh + 1 order of RamanRayleighfor all
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Perturbation theory approach: expansion of the Greens functionaDDbGrayabGrayGrayGrayGrayGrayaDb-+- ...Rayleigh + 1 order of RamanRayleigh + 2 orders of RamanRayleighfor allfor all
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Perturbation theory approach: expansion of the Greens functionaDDbGrayabGrayGrayGrayGrayGrayaDb++- ...Rayleigh + 1 order of RamanRayleigh + 2 orders of RamanRayleighfor allfor allbw
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Comparison pert - daFilling-in[%]
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Comparison pert - daFilling-in[%]Differencepert - da
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PolarizationStokes vector
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Polarization
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Neglect of polarizationError filling-in[%]
scalar -vectorErrorcontinuum[%]
scalar -vector
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The simulated Ring effect depends on the input solar spectrum
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Using a retrieved solar spectrum insteadClear skyland
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ConclusionRadiative transfer problem including Raman scattering involves scattering from one direction to another direction &from a certain wavelength to another wavelength1. Neglecting multiple Raman scattering: errors < 0.6 %
2. Neglecting polarization: errors < 0.2 % on filling-inScalar approach can be used to simulate Ring effect.Polarization effects mainly due to elastically scattered radiation.
3.Different input solar spectra: differences up to 8%Solution: construct a solar spectrum on a high resolution wavelength grid from the measurements. Better than 0.5%.AnswersChallenge
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Thank you for your attentionwww.sron.nl/[email protected]
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Backup slides
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The doubling-adding productInvolves integration over all possible angles AND all possible wavelengths(Use optimized wavelength grid, only relevant bins)
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Optimizing the wavelength grid( w + ww + www )/3( w + ww )/2wwwavenumber shift [cm-1]orderof scattering
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Optimizing the wavelength gridorderof scattering( w + ww + www )/3( w + ww )/2wwwavenumber shift [cm-1]threshold
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Polarization: the phase matrix elementsP11ramP11cabQQQQQP33ramP22ramP21ramP44ramP22cabP21cabP33cabP44cabP34 = 0
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How much multiple Raman scattering?total Raman scattering fractionreflectivity multiple Ramanscattering fraction
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Using the retrieved solar spectrum (A)
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Using the retrieved solar spectrum (B)
Today, modeling of Raman scattering in the Earths atmosphere
Satellite instruments measure backscattered radiationoften talked about about absorptionScattering, you dont see anything without scattering
A small fraction is inleatsiclayy scattered..
I am going to talk about modeling this scattered radaitionThe restrioctions and challenges that are involved.
Much structure UV 240-400 nmless towards IRTwo modelswe can study two questions
multiple orderr of Raman scattering
one order of Raman scatteringVandaag:modeleren van GOME spectraFocus: fijne spectrale structuren
1. Meting laten zien+fjne structuren2. Sterkte van deze structuren