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Modeling rotational Raman scattering in the Earth’s atmosphere

Modeling rotational Raman scattering in the Earth’s atmosphere. Rutger van Deelen Jochen Landgraf Otto Hasekamp Ilse Aben. September 13, 2006, KNMI. Three questions. Multiple scattering. Multiple Raman scattering? Polarization? Dependence on input solar spectrum?. Measured GOME spectra.

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Modeling rotational Raman scattering in the Earth’s atmosphere

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  1. Modeling rotational Raman scattering in the Earth’s atmosphere Rutger van Deelen Jochen Landgraf Otto Hasekamp Ilse Aben September 13, 2006, KNMI

  2. Three questions Multiple scattering. Multiple Raman scattering? Polarization? Dependence on input solar spectrum?

  3. Measured GOME spectra solar irradiance spectrum Earth radiance spectrum

  4. The GOME reflectivity spectrum

  5. The GOME reflectivity spectrum Raman

  6. Rotational Raman scattering AIR (N2, O2) Cabannes 96 % elastic Raman 4 % inelastic Raman

  7. Filling-in

  8. Filling-in

  9. Perturbation theory approach Doubling-addingapproach multiple orders of Raman scattering, comes out naturally, scalar one order of Raman scattering, fast, vector wP wP wP wP wP A

  10. Rayleigh optical thickness tray(l) single scattering albedo wray(l) Pray phase function Q

  11. Rayleigh Cabannes + Raman optical thickness tray(l) tray(l’) = tcab(l’) + S tram(l,l’) l total elastic inelastic wcab(l) inelastic single scattering albedo wram(l,l’) wray(l) w(l,l’) Pray Pcab phase function Q Q Pram

  12. Doubling-adding approach R T

  13. Doubling-adding approach R T Rab a b Tab

  14. Perturbation theory approach: based on the Green’s function (z’,l’,W’) a b (z,l,W)

  15. Perturbation theory approach: based on the Green’s function G = G(z,l,W;z’,l’,W’) (z’,l’,W’) a G b arrow includes multiple scattering! (z,l,W) describes how the atmosphere responds to light

  16. Perturbation theory approach: based on the Green’s function b a source and target are fixed G arrow includes multiple scattering! Dyson series G = Gray – Gray [ D Gray ] + Gray [ D Gray ]2 – Gray [ D Gray ]3+ …

  17. Perturbation theory approach: expansion of the Green’s function b a Gray Rayleigh

  18. Perturbation theory approach: expansion of the Green’s function b a b a Gray Gray Gray - D for all Rayleigh + 1 order of Raman Rayleigh

  19. Perturbation theory approach: expansion of the Green’s function b a b a b a Gray Gray Gray Gray D Gray - ... - D + D Gray for all for all Rayleigh + 1 order of Raman Rayleigh + 2 orders of Raman Rayleigh

  20. Perturbation theory approach: expansion of the Green’s function b a b a b a Gray Gray Gray Gray D bw Gray - ... + D + D Gray for all for all Rayleigh + 1 order of Raman Rayleigh + 2 orders of Raman Rayleigh

  21. Comparison pert - da Filling-in [%]

  22. Comparison pert - da Filling-in [%] Difference pert - da

  23. Polarization Stokes vector

  24. Polarization

  25. Neglect of polarization Error continuum [%] scalar -vector Error filling-in [%] scalar -vector

  26. The simulated Ring effect depends on the input solar spectrum

  27. Using a retrieved solar spectrum instead Clear sky land

  28. Conclusion Radiative transfer problem including Raman scattering involves scattering from one direction to another direction & from a certain wavelength to another wavelength Challenge Answers 1.Neglecting multiple Raman scattering: errors < 0.6 % 2.Neglecting polarization: errors < 0.2 % on filling-in Scalar 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%.

  29. Thank you for your attention www.sron.nl/raman r.van.deelen@sron.nl

  30. Backup slides

  31. The doubling-adding product Involves integration over all possible angles AND all possible wavelengths (Use optimized wavelength grid, only relevant bins)

  32. Optimizing the wavelength grid w w (w+ww)/2 order of scattering (w+ww+www)/3 wavenumber shift [cm-1]

  33. Optimizing the wavelength grid w w threshold (w+ww)/2 order of scattering (w+ww+www)/3 wavenumber shift [cm-1]

  34. Polarization: the phase matrix elements P11cab P21cab P22cab P33cab P44cab Q Q Q Q Q P11ram P21ram P22ram P33ram P44ram P34 = 0

  35. How much multiple Raman scattering? reflectivity total Raman scattering fraction multiple Raman scattering fraction

  36. Using the retrieved solar spectrum (A)

  37. Using the retrieved solar spectrum (B)

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