RTTOV - the fast radiative transfer model for calculations of radiances for satellite infrared or microwave nadir scanning radiometers (see push broom scanner).
The range of temperatures and water vapour concentrations over which the optical depth computations are valid depends on the training datasets which were used.
RTTOV contains forward, tangent linear, adjoint and K (full Jacobian matrices) versions of the model; the latter three modules for variational assimilation or retrieval applications.
FASTEM2 computes the surface emissivity averaged over all facets representing the surface of the ocean and an effective path correction factor for the down-welling brightness temperature.
FASTEM2 is applicable for frequencies between 10 and 220 GHz, for earth incidence angles less than 60 degrees.