Radiative Transfer Equation (IR)

Thetai,calc = B-1nu(Ri,calc)
Ri,calc = epsilon"i Bi(Ts) + rho'i Hi tau'i(ps) cos(theta0) + integ Bi(T(p)) (dtauui/dln p) (dln p) + rhoi tauui(ps) integ Bi(T(p)) (dtaudi/dln p) (dln p)

Bi(T) is the Planck function evaluated at the effective channel wavenumber.
Hi is the channel averaged solar irradiance at the top of the atmosphere.
theta0 is the local zenith angle of the Sun.
tau'i is the channel averaged two path transmittance from the Sun to the surface to the satellite.
tauui(p) is the atmospheric transmittance measured between p and the top of the atmosphere for channel i.
taudi(p) is the atmospheric transmittance between p and the surface for channel i.

Explicit retrieved parameters
epsiloni is the surface emissivity at nui.
Ts is the surface temperature.
T(p) is the surface temperature profile.
rhoi is the surface spectral reflectivity at nui.
rho'i is the surface spectral bidirectional reflectance of solar radiation at nui.

Implicit retrieved parameters ( i.e., within taui and tau'i).
CO2(p) is the carbon dioxide profile.
q(p) is the humidity (water) profile.
O3(p) is the ozone profile.
CO(p) is the carbon monoxide profile.
CH4(p) is the methane profile.
NO2(p) is the nitrogen dioxide profile.