Radiative Transfer Radiative transfer equation (RTE) - IAP ...

Scattering of radiation
◮ The scattering cross section is a kind of shadow
However this ’shadow’ can be bigger than the actual
geometrical cross section
◮ The ratio of the scattering cross section to the
geometrical area A is called scattering efficiency:
Q s = σ s
A
◮ Q s in general will be a strong function of λ and ε
◮ For visible wavelength σ s of air molecules is approx.
proportional to 1/λ 4 → Rayleigh scattering
◮ Rayleigh scattering explains blue sky and red sunsets
and sunrises
◮ The loss of radiation along a line-of-sight due to
scattering is always associated with a gain in radiation
along other lines-of-sight
⇒ source term in radiative transfer
RTE
Beer’s law
Abs. cross section
Opacity &
Transmission
Mean free path
Scattering
Schwarzschild eq.