Absorption Stuff:

1D / 2D:

Input Atmosphere stuff is 1D, so is RTE. Only the absorption
coefficient calculation itself is already 2D, since this is
practically no extra effort.

Reason for 1D input: It is not enough to just read a list of
profiles. They could be on different horizontal grids. In fact one
must somehow specify the horizontal coordinate to do proper horizontal
interpolation.