Sciatran - a new radiative transfer model for geophysical applications in the 240–2400 NM spectral region: the pseudo-spherical version Original Research Article

A radiative transfer model, SCIATRAN, has been developed mainly for the retrieval of atmospheric constituents from global nadir radiance measurements of the SCIAMACHY satellite spectrometer. This is a further development of the successful GOMETRAN. SCIATRAN solves the radiative transfer equation using the Finite Difference Method for a plane-parallel vertically inhomogeneous atmosphere taking into account multiple scattering. The present program version utilizes the pseudo-spherical approach, including refraction, appropriate for solar zenith angles up to about 92°. SCIATRAN comprises, amongst others, the following features: (i) quasi-analytical calculation of weighting functions of atmospheric and surface parameters, (ii) DOAS airmass factor calculations, (iii) height resolved radiation fluxes, including actinic fluxes for photolysis rate calculations, (iv) inelastic rotational Raman scattering by N2 and O2 molecules, (v) parameterization schemes for aerosols and clouds, (vi) a line-by-line and a correlated-k distribution mode for line absorption, and (vii) thermal emission. This paper presents an overview of the SCIATRAN model, focusing on the pseudo-spherical approach developed to consider the sphericity of the Earth. SCIATRAN will be made available via the world wide web for non-commercial scientific applications.