1. Radiation: WHY CARE ??? the ultimate energy source, driver for the general circulation usefully applied in remote sensing (more and more)

2. Sun Earth Y-axis: Spectral radiance, aka monochromatic intensity units: watts/(m^2*ster*wavelength) Blackbody curves provide the envelope to Sun, earth emission

3. All objects radiate Blackbody: absorbs all, reflects none, emits isotropically Blackbody radiation observed first, only later described (Max) Planck function Integrated over all wavelengths: E=  T 4 ;  x 10 -8 W m -2 K -4 ; E is called irradiance, flux density. Units of W/m^2

4. Wien’s Law wavelength of the peak emission from dE/d(wavelength) = 0 Wavelength max (in microns) = 2897/T (in Kelvin) For Sun, = 6000 K, for Earth = 255 K => max. wavelength Sun = 0.475 micron (blue), max wavelength Earth ~ 14 micron. Explains spectral Distribution of radiation

5. Energy absorbed from Sun establishes Earth’s mean T F sun = 1368 W m -2 @ earth Energy in=energy out F sun *pi*R 2 earth = 4*pi*R 2 earth *(1.-albedo)*(sigma*T 4 earth ) global albedo ~ 0.3 => T earth = 255 K This + Wien’s law explains why earth’s radiation is in the infrared

8. Sun Earth visible

9. 1 Angstrom= 10 -10 m. Photoionization @ wavelengths < 0.1 micron (1000 angstroms) Photodissociation @ wavelengths 2O Ozone dissociation @wavelengths < 0.31 micron Depth of penetraion into earth’s atmosphere of solar UV Visible spectrum 0.39 to 0.76 micron

10. To understand Earth’s emission need….. Kirchoff’s Law: emissivity = absorptivity, for a given wavelength Also called Local Thermodynamic Equilibrium (LTE) Holds up to 60 km

11. High solar transmissivity + low IR transmissivity = Greenhouse effect Consider multiple isothermal layers, each in radiative equilibrium. Each layer, opaque in the infrared, emits IR both up and down, while solar is only down Top of atmosphere: F in = F out incoming solar flux = outgoing IR flux At surface, incoming solar flux + downwelling IR = outgoing IR => Outgoing IR at surface, with absorbing atmosphere > outgoing IR with no atmosphere 1. 2.

12. Manabe&Strickler, 1964: Note ozone, surface T

13. Radiation transmits through an atmospheric layer According to: I = intensity r= air density r = absorbing gas amount k =mass extinction coeff.  rk = volume extinction coeff. Inverse length unit Extinction=scattering+absorption Path length ds

14. Whether/how solar radiation scatters when it impacts gases,aerosols,clouds,the ocean surface depends on 1. ratio of scatterer size to wavelength: Size parameter x = 2*pi*scatterer radius/wavelength X large X small Sunlight on a flat ocean Sunlight on raindrops IR scattering off of air, aerosol Microwave scattering off of clouds Microwave (cm) Scattering neglected

15. Rayleigh scattering: solar scattering off of gases proportional to (1/   aerosol Cloud drops R=10 -4  m R=1  m R=0.1  m Solar scattering Gas (air) Mie scattering: 1 < x < 50

16. Mie scattering: solar scattering off of cloud water and ice microwave scattering off of precipitation Index of refraction is complex: real part = scattering imagery component=absorption m real =1.33 for water, 1.3 for ice

17. water

18. Mie scattering: algorithms for spherical drops work very well. Calculated radiance depends on drop size, wavelength, indx of refraction Forward scattering In direction of light Backward scattering Back towards viewer

19. Secondary rainbox at 51 degrees

20. Glory: around the shadow of your head, or an airplane, At the anti-solar point. - need small drops Corona: often seen around the moon “Heiligenschein”