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/ramanr.van.deelen@sron.nl

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