Modeling rotational Raman scattering in the Earth’s atmosphere Rutger van Deelen Jochen Landgraf Otto Hasekamp Ilse Aben September 13, 2006, KNMI
Mar 19, 2016
Modeling rotational Raman scattering in the Earths atmosphereRutger van DeelenJochen Landgraf Otto HasekampIlse Aben
September 13, 2006, KNMI
Three questionsMultiple scattering. Multiple Raman scattering?
Polarization?
Dependence on input solar spectrum?
Measured GOME spectrasolar irradiance spectrumEarth radiance spectrum
The GOME reflectivity spectrum
The GOME reflectivity spectrumRaman
Rotational Raman scatteringCabannes96 % elasticRaman4 % inelasticAIR (N2, O2)Raman
Filling-in
Filling-in
Doubling-addingapproachPerturbation theory approachw Pw Pw Pw PAw Pmultiple orders of Raman scattering,comes out naturally,scalarone order of Raman scattering,fast,vector
Rayleighwray(l)tray(l) single scattering albedooptical thicknessphasefunctionPrayQ
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
Doubling-adding approachRT
Doubling-adding approachRTRabTabab
Perturbation theory approach: based on the Greens functiona(z,l,W)b(z,l,W)
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
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!
Perturbation theory approach: expansion of the Greens functionabGrayRayleigh
Perturbation theory approach: expansion of the Greens functionabGrayabGrayGrayD-Rayleigh + 1 order of RamanRayleighfor all
Perturbation theory approach: expansion of the Greens functionaDDbGrayabGrayGrayGrayGrayGrayaDb-+- ...Rayleigh + 1 order of RamanRayleigh + 2 orders of RamanRayleighfor allfor all
Perturbation theory approach: expansion of the Greens functionaDDbGrayabGrayGrayGrayGrayGrayaDb++- ...Rayleigh + 1 order of RamanRayleigh + 2 orders of RamanRayleighfor allfor allbw
Comparison pert - daFilling-in[%]
Comparison pert - daFilling-in[%]Differencepert - da
PolarizationStokes vector
Polarization
Neglect of polarizationError filling-in[%]
scalar -vectorErrorcontinuum[%]
scalar -vector
The simulated Ring effect depends on the input solar spectrum
Using a retrieved solar spectrum insteadClear skyland
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
Thank you for your attentionwww.sron.nl/[email protected]
Backup slides
The doubling-adding productInvolves integration over all possible angles AND all possible wavelengths(Use optimized wavelength grid, only relevant bins)
Optimizing the wavelength grid( w + ww + www )/3( w + ww )/2wwwavenumber shift [cm-1]orderof scattering
Optimizing the wavelength gridorderof scattering( w + ww + www )/3( w + ww )/2wwwavenumber shift [cm-1]threshold
Polarization: the phase matrix elementsP11ramP11cabQQQQQP33ramP22ramP21ramP44ramP22cabP21cabP33cabP44cabP34 = 0
How much multiple Raman scattering?total Raman scattering fractionreflectivity multiple Ramanscattering fraction
Using the retrieved solar spectrum (A)
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