Rotational Raman scattering in the Earth's atmosphere ... - SRON

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3.3.3 The perturbation integrals of first order 51 3.4 Simulation of reflectance spectra 52 3.4.1 Rotational Raman scattering and polarization spectra 52 3.4.2 Approximation methods 58 3.5 Simulation of polarization sensitive measurements of GOME including Ring structures 62 3.6 Summary 70 3.A Appendix: Optical properties of rotational Raman, Cabannes and Rayleigh scattering 71 3.B Appendix: The Fourier expansion 73 3.C Appendix: Evaluation of the perturbation integrals 76 4 Accurate modeling of spectral fine-structure in Earth radiance spectra measured with the Global Ozone Monitoring Experiment 79 4.1 Introduction 79 4.2 GOME measurements 81 4.3 The GOME reflectivity spectrum 84 4.4 Retrieval of a solar spectrum on a fine spectral grid from the solar measurement 88 4.4.1 Inversion scheme 88 4.4.2 Undersampling error 89 4.4.3 Simulation of GOME earthshine measurements 91 4.5 Retrieval of a solar spectrum on a fine spectral grid from the combination of an earthshine and a solar measurement 93 4.6 Conclusion 95 5 Retrieval of cloud properties from near ultraviolet, visible and near infrared satellitebased Earth reflectivity spectra: a comparative study 97 5.1 Introduction 98 5.2 Forward model 99 5.3 Sensitivity of measurement to cloud properties 101 5.4 Inversion and retrieval diagnostics 104 5.5 Information content of the NUV, VIS and NIR spectral window 106 5.6 The synergistic use of spectral windows 112 5.7 Summary and conclusion 114 References 119 Summary 127 Samenvatting 131 List of publications 135
1 Introduction 1.1 Observing skylight Looking through an airplane window one can admire the deep blue color of the sky. This blue color arises from molecules in the Earth’s atmosphere, of which the most abundant species in the dry atmosphere are: nitrogen (N 2 ; volume mixing ratio of 78.09%), oxygen (O 2 ; 20.95%), and argon (Ar; 0.93%). These molecules, which have diameters that are more than a thousand times smaller than the wavelength of the incident sunlight, scatter sunlight in all directions [Minnaert, 2004]. Light with short wavelengths (i.e blueish light) is more strongly scattered than light with longer wavelengths. The human eye contains two groups of light receptor cells, the rods and cones. The rods are sensitive to dim light and mediate coarse black and white vision. The cones are specialized for daylight and come in three types 1 that mediate detailed color vision [Stockman and Sharpe, 2000]. When looking at the sky the cones that are most sensitive to blue light are triggered more than the ones that predominantly sense blueish-green and yellowish-green light. This information is sent to the brain where the image of a blue sky is formed [Kandel et al., 1991]. Over the past centuries a plethora of instruments has been developed that complement our eyes and brains. Sir Isaac Newton (1643–1727) demonstrated with a simple glass prism that light is composed of different colors. Spectrometers can be built that accurately measure this, i.e. the intensity of light as a function of wavelength. It was found that visible light covers only a small part (400–700 nm) of the whole spectrum of electromagnetic radiation. Development of new detector technology enabled humans to study spectra of invisible radiation as well. During the last decades of the twentieth century satellites have been launched with spectrometers on board. These space-borne spectrometers act as artificial ‘eyes in the sky’ that monitor the Earth from above. Unlike our eyes that contain three types of spectral detectors 2 , many of these spectrometers contain several thousand different spectral detectors that together cover a similar wavelength range as the human eye. Examples of such space-borne spectrometers are the Global Ozone Monitoring Experiment and its successor (GOME and GOME-2), the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and the Ozone Monitoring Experiment (OMI). Table 1.1 lists several properties of these spectrometers. 1 Approximately 8% of the male readers of this thesis has effectively two types of cones and is thus color blind. 2 The spectral responses of the three types of detectors in the human eye (the S, M and L cone) show a maximum near 442 nm, 543 nm and 570 nm, and have a full width at half maximum of 57 nm, 85 nm, and 111 nm, respectively [Stockman and Sharpe, 2000].
Page 1 and 2: VRIJE UNIVERSITEIT Rotational Raman
Page 5: Contents 1 Introduction 1 1.1 Obser
Page 9 and 10: Introduction 3 Extracting the wealt
Page 11 and 12: Introduction 5 and Spurr, 1997, Vou
Page 13 and 14: Introduction 7 energy: E rot (v,J)
Page 15 and 16: Introduction 9 Figure 1.4: Probabil
Page 17 and 18: Introduction 11 scattered radiance
Page 19 and 20: Introduction 13 approximation in wh
Page 21 and 22: Introduction 15 scattering have bee
Page 23 and 24: 2 A doubling-adding method to inclu
Page 25 and 26: A doubling-adding method to include
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Page 48 and 49: 42 Chapter 3 contributions of lower
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50 Chapter 3 The forward and adjoin
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52 Chapter 3 Here, ∆ = diag [1, 1
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54 Chapter 3 Figure 3.3: Relative R
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56 Chapter 3 biases the simulation
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58 Chapter 3 3.4.2 Approximation me
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60 Chapter 3 where I ram,app and I
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62 Chapter 3 3.5 Simulation of pola
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64 Chapter 3 Figure 3.10: Relative
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66 Chapter 3 dependence on the vert
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68 Chapter 3 Figure 3.13: Same as F
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70 Chapter 3 3.6 Summary A vector r
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72 Chapter 3 where λ is the wavele
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74 Chapter 3 where S l is the expan
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76 Chapter 3 3.C Appendix: Evaluati
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4 Accurate modeling of spectral fin
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References Aben, I., F. Helderman,
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References 121 Ellery, A., D. Wynn-
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References 123 Lacis, A. A., J. Cho
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References 125 Schulz, F., K. Stamn
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Summary A spectrum of sunlight that
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Summary 129 Earth radiance spectrum
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Samenvatting Het door de aardatmosf
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Samenvatting 133 met een vector-mod
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List of publications Peer-reviewed
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