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AT737

AT737. Radiative Transfer 1. Overview. Goal: Measure parameter A ( x, y, z, t ) Develop satellite INSTRUMENT such that: A “digital count,” C I , from the instrument system results from the detection of a “spectral radiance” L l ( A ) from the parameter A.

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AT737

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  1. AT737 Radiative Transfer 1

  2. Overview • Goal: Measure parameter A(x, y, z, t) • Develop satellite INSTRUMENT such that:A “digital count,” CI, from the instrument system results from the detection of a “spectral radiance” Ll(A) from the parameter A. AT737 Radiative Transfer

  3. Develop a scientific ALGORITHM to input the measured “digital count” and output the parameter A in physical units:“other” terms in the algorithm account for unwanted “masking phenomena.” Overview (cont.) AT737 Radiative Transfer

  4. Overview (cont.) • Develop and apply the TIME/SPACE SAMPLING strategy to measure A(x, y, z, t) • From a specific satellite orbit • From an instrument with specific characteristics • At intervals related to the variation of A(x, y, z, t) AT737 Radiative Transfer

  5. The Fundamental Challenge • Satellites sense ONLY electromagnetic radiation. • Meteorological quantities must be inferred from the radiation measurements. • Understanding the sources of radiation and its interaction with the atmosphere and surface is essential. AT737 Radiative Transfer

  6. Detector Radiation Telescope Electronics Filter Basic Quantities • Radiance, Ll = energy/time/area/solid angle/wavelength interval AT737 Radiative Transfer

  7. Basic Quantities (cont.) • Radiant Exitance/Irradiance AT737 Radiative Transfer

  8. Blackbody Radiation • The Planck Function AT737 Radiative Transfer

  9. Non-Blackbodies • Emittance AT737 Radiative Transfer

  10. Non-Blackbodies (cont.) • Kirchhoff’s Law Blackbodies are perfect emitters, el = 1. By Kirchhoff’s Law, they are also perfect absorbers, al= 1, which is why they look black. AT737 Radiative Transfer

  11. The Radiative Transfer Eqn. AT737 Radiative Transfer

  12. The RTE (cont.) Term A = absorption by material in the volume Beer’s Law sa(l) = volume absorption coefficient (m-1) Term B = emission by material in the volume AT737 Radiative Transfer

  13. The RTE (cont.) Term C = scattering of radiation out of the beam ss(l) = volume scattering coefficient (m-1) AT737 Radiative Transfer

  14. The RTE (cont.) Term D = scattering of radiation into the beam ys = scattering angle p(ys) = scattering phase function AT737 Radiative Transfer

  15. The RTE (cont.) The Radiative Transfer Equation: Term A Term B Term C Term D AT737 Radiative Transfer

  16. Note that Therefore And the RTE becomes The RTE Simplified AT737 Radiative Transfer

  17. No-Scattering RTE Schwarzchild’s Equation AT737 Radiative Transfer

  18. Integrated Schwarzchild’s Eqn. AT737 Radiative Transfer

  19. No-Emission RTE AT737 Radiative Transfer

  20. No-Emission RTE (cont.) AT737 Radiative Transfer

  21. Next time… AT737 Radiative Transfer

  22. Gaseous Absorption AT737 Radiative Transfer

  23. Scattering AT737 Radiative Transfer

  24. Surface Reflection AT737 Radiative Transfer

  25. Solar Radiation AT737 Radiative Transfer

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