Verification of radiative transfer results by inserting them into the RTE: A demonstration for Rayleigh scattering

The verification of a new or updated radiative transfer model (RTM) is one of the important steps in its development; this is usually achieved by comparisons with real measurements or published tables of generally accepted radiative transfer results. If such tables do not exist, verification becomes more complicated and an external review of the implementation is often unpractical due to the sheer amount and complexity of the code. The presented verification approach is to "simply" insert results of radiative transfer (RT) calculations into the radiative transfer equation (RTE). The evaluation of the RTE consists of numerically calculating partial derivatives and integrals, which is much simpler to implement than a solution of the RTE. Presented is a demonstration of this approach for a case of Rayleigh scattering in a plane parallel atmosphere, which showed only very small deviation from the radiative transfer equation. This approach has two key benefits. First, its implementation into a high level computer language can be very short (≈60 lines in MATHEMATICA) and clear compared to a full RTM; and such code is much more easy to review. Second, this approach can be easily extended to cases where no other independent RT implementation is available for validation. The proposed implementation and data are provided with this paper. -- Highlights: ► Radiative transfer results are verified by numerically inserting them into the RTE. ► This approach is demonstrated using a Rayleigh scattering test case. ► The implementation of such verification scheme is simple, short, and clear. ► The scheme and the demonstration data set is provided with the paper.