The [rte_lw()](/reference/rte-fortran-interface/proc/rte_lw.html) and [rte_sw()](/reference/rte-fortran-interface/proc/rte_sw.html) routines in the RTE library compute radiative transfer on a user-specified problem. Both routines allow for an upper boundary condition for spectrally-resolved diffuse radiation. rte_sw() is overloaded to allow users to specify either a single value of mu0 per column or a value at each layer of each column.

If optical properties are specified as variables of type ty_optical_props_1scl (meaning extinction optical depth alone) in the longwave, radiative transfer is computed accounting for only emission and absorption. If optical properties are specified as variables of type ty_optical_props_2str (optical depth, single-scattering albedo, and asymmetry parameter) the rescaling and refinement method of Tang et al. 2018 is used by default; two-stream and adding methods maybe be chosen by setting optional argument use_2stream to .TRUE.

The sensitivity of broadband flux (W/m$^2$-K) to changes in surface temperature is available in optional output argument flux_up_Jac . Jacobians are not available if use_2stream is ``.TRUE.`