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Chapter 12: Scattering and Absorption by Particles

Chapter 12: Scattering and Absorption by Particles. Summary of Scattering Regimes: Note Particle Sizes and wavelengths of radiation!!. Accelerating Dipole Moment Produces Rayleigh Scattering. P. . q. -. dipole moment =P =Q x=  E 0  =polarizability. +. E 0. x. -. +. Charge Q.

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Chapter 12: Scattering and Absorption by Particles

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  1. Chapter 12: Scattering and Absorption by Particles Summary of Scattering Regimes: Note Particle Sizes and wavelengths of radiation!!

  2. Accelerating Dipole Moment Produces Rayleigh Scattering P  q - dipolemoment =P=Qx=E0 =polarizability + E0 x - + Charge Q Acceleration of dipole moment: Scattered E field!!!

  3. Rayleigh Scattering Phase Function: Angular Distribution of Light Scattered by a Dipole Refer to last page for polarization states. horizontal polarization vertical polarization average of both

  4. Rayleigh Scattering Phase Function: Angular Distribution of Light Scattered by a Dipole vertical polarization state 3D rendering horizontal polarization state The Peanut! Average of both polarization states.

  5. Mie Theory for Water Spheres (non absorbing) Maximum, relative maxima and minima, approximate theor due to Rayleigh.

  6. Mie Theory for Water Spheres: m=1.33, Visible Wavelengths

  7. Mie Theory for Absorbing and Scattering Spheres modest ni has the largest absorption for modest size parameters.

  8. Mie Phase Functions for Water Spheres Note the dipole character for small x and the primary and secondary rainbows for large x.

  9. Mie Phase Functions for Water Spheres: Log[p()] for details Glory (strong backscattering, rainbow, and corona are clearly visible. Fogbow is ‘rainbow’ for small size parameter.

  10. Mie Theory for Water and Ice Spheres Absorption feature good for phase determination.

  11. Mie Radar Backscatter Efficiency for Water and Ice Spheres Non Rayleigh strong backscatter by water drops compared to that of ice!! Rayleigh WSR-88D NWS Doppler Radar

  12. Radar Bright Band: Strong Scattering from Melting Hydrometeors http://www.radar.mcgill.ca/bright_band.html

  13. Mass Absorption Coefficient for Cloud Water Spheres, Microwaves Microwave remote sensing for cloud water path L: TB = T = [1-exp(-kL)] T (Rayleigh Jeans Approximation for brightness temperature) T microwave radiometer

  14. Zenith Microwave Transmittance: Cloud Free Atmospheres Water Vapor Rotational Lines Choose microwave frequencies for cloud emissivity measurement wheretransmittance is high!!! Water vapor is variable; choose low frequency.

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