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Illumination Independent Aerosol Optical Properties

Illumination Independent Aerosol Optical Properties. Extinction Scattering Absorption Volume scattering function (phase) Transmittance. Extinction =. The extinction coefficient is made up of particle and gas scattering and absorption:

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Illumination Independent Aerosol Optical Properties

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  1. Illumination Independent Aerosol Optical Properties • Extinction • Scattering • Absorption • Volume scattering function (phase) • Transmittance

  2. Extinction = The extinction coefficient is made up of particle and gas scattering and absorption: where s, a, g, and p refer to scattering, absorption, gases, and particles, respectively.

  3. Components of Scattering and Extinction

  4. Animations of scattering and absorption

  5. One Approximation for Estimating bext

  6. Extinction as Function of Size where Eeis mass extinction efficiency, f i(x) is the aerosol mass distribution dm/dx of the ith species, x=ln[D/Do], and λ is the wavelength.

  7. Externally Mixed Model where and for multiple species

  8. Scattering Efficiency (Q)

  9. Single Particle Efficiency

  10. Particle Size Distribution

  11. Scattering Efficiency as Function of Size

  12. Carbon Extinction Efficiency

  13. Phase Function for Soil and Sulfate

  14. Phase Function for Carbon

  15. Forward and Backward Scattering

  16. Pollutant Species

  17. Primary vs. Secondary Particles and Gases (Pollutants) • Primary particles and gases are those emitted into the atmosphere directly from some source. • Secondary particles and gases are formed in the atmosphere by chemical reactions, by condensation growth, and/or by coagulation.

  18. Particle Size Distribution

  19. Anthropogenic Wind Blown Dust Roads, Over Grazing, Farming practices, Mining Biomass Burning Land Clearing Practices Emissions from fossil fuel combustion Fly Ash Condensation of Hot Vapors Naturally Occurring Wind Blown Dust Deserts Volcanoes Fires Plant Particles (pollen) Sea Salt Spray (NaCl) Sources of Primary Particles

  20. Sources of Primary Gases Important to Secondary Particle Formation Compound Anthropogenic Naturally Occurring SO2 Volcanoes Fossil-Fuel Smelters Oil Refining NOx Fossil-Fuel Combustion Mobil Sources Soil Release (Fertilizer) Soil Release Lightning NH3 Farm Animals Wild Animals Vegetation Ocean Volatile Organics Mobile Sources Vegetation

  21. Hygroscopic Aerosols • Water uptake by particles in the atmosphere • Aerosol particles grow and scatter more light • Deliquescence - the RH value at which the crystal begins to absorb water and becomes a solution droplet • Hysteresis - water is retained on the particle at RH values lower than predicted by equilibrium

  22. Growth of Sulfate

  23. Hygroscopic Growth of Particles

  24. Ammonium Sulfate D/Do Curves

  25. Two Measured f(RH) Curves and Theoretical Estimated

  26. F(rh) for Grand Canyon

  27. Estimated f(rh) for Sulfate and Organics

  28. Internally Mixed Aerosol however,

  29. Mass Removal Issues

  30. Partial Scattering Efficiency From previous equations, it is apparent that changes in visibility that correspond to changes in aerosol species concentrations can be expressed by forming the derivativeτr/Ci, whereCi refers to the concentration of particulate species i, and that this derivative will have terms containing the derivative bext/Ci. Therefore, define partial scattering efficiency as:

  31. Extinction for External and Internal Mixture

  32. D/Do Curves for Partial Scattering Calculation

  33. Partial Scattering Efficiency for External and Internally Mixed Aerosols

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