Pat Arnott, ATMS 749 Atmospheric Radiation Transfer CH4: Reflection and Refraction in a Homogenous Medium.

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Polarization States: A reminder Wave/Photon boson: Polarization. Linear Polarization: E-field in one direction. Circular, elliptical polarization: E-Efield rotates due to phase difference between horizontal and vertical components. From:

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer More Details on the Polarization States Circular Polarization Elliptical Polarization: The most general representation.

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Three Choices for Solar Radiation Emissivity is the same as absorptivity. Source can be visible or infrared radiation, or other wavelengths as well, microwave, etc. Transmission + Reflection + Absorption = 1

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Reflection, Refraction, and Transmission

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Radiant Intensity and Flux: How do we deal with reflected radiation? What are examples of each type of reflection?

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Trace velocity matching principle: Snell’s law (continuity of the wavefront at a boundary) “slow is more normal” Here assume n 1 =n 1r, n 1i =0, n 2 =n 2r, n 2i =0. MIRAGES n 1 sin(  1 )= n 2 sin(  2 ) For a gas, (n r -1) ≈   =gas density. d  /dz > 0 for this type or mirage. What does this say about the likelihood of convection? z Another type of reflection without a real interface.

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Snell’s Law: Kinematics

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Complex Refractive Index for Water and Ice

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Some Basics, Electromagnetic Skin Depth

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Wave Penetration Depth in Water and Ice

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Boundary Conditions at Interfaces: Used with Plane Wave Solutions of Maxwell’s Equations for E and H to get the Fresnel Coefficients. Used along with boundary conditions to calculate the single scattering properties of aerosols and hydrometeors (cloud droplets, rain drops, ice crystals, snow flakes, etc), from first principles if possible. {Mie theory for homogeneous spheres, coupled dipole theory for general particles, T-Matrix method, etc} Are not used to calculate the radiation field arriving at the surface from the complex atmosphere. Multiple scattering theory is used.

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Fresnel Reflection Coefficients: What is the magnitude of the light specularly reflected from a surface? (Also can get the transmitted wave magnitude). Medium 2 Medium 1 ii tt

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Reflectivity of Water And Ice Brewster Angle Microwave =15,000 microns n r = n i = Mid Visible (green) =0.5 microns n r = n i = x

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Reflectivity of Water And Ice: Normal Incidence What drives the reflectivity?

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Geometrical Optics: Interpret Most Atmospheric Optics from Raindrops and lawn sprinklers (from Wallace and Hobbs CH4) Rainbow from raindrops Primary Rainbow Angle: Angle of Minimum Deviation (turning point) for rays incident with 2 chords in raindrops. Secondary Rainbow Angle: Angle of Minimum Deviation (turning point) for rays incident with 3 chords in raindrops.

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Rainbow Optics scattering angle  See and atmospheric optics. atmospheric optics nrnr

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Geometrical Optics: Rainbow (from Petty) Angle of minimum deviation from the forward direction. Focusing or confluence of rays. x Distance x is also known as the impact parameter. (Height above the sphere center.)

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Geometrical Optics: Interpret Most Atmospheric Optics from Ice Crystals (from Wallace and Hobbs CH4) 22 deg and 45 deg Halos from cirrus crystals of the column or rosette (combinations of columns) types. Both are angle of deviation phenomena like the rainbow. Crystal orientation important. 22 deg halo, more common, thumb rule to measure size of arc.

Pat Arnott, ATMS 749 Atmospheric Radiation Transfer Light Scattering Basics (images from Wallace and Hobbs CH4). Sphere, radius r, complex refractive index n=m r + im i x x x m r =1.5 QsQs Angular Distribution of scattered radiation (phase function) x x x Dipole scattering