A Comparison of Three Radiative Transfer Algorithms

This study focuses on three radiative transfer algorithms: The Community Radiative Transfer Algorithm (CRTM), Radiative Transfer for TOVS (RTTOVS), and the Stand Alone AIRS Radiative Transfer Algorithm (SARTA). CRTM and RTTOVS both produce cloudy hyperspectral radiances for the AIRS instrument through scattering parameterizations. A delta four stream scattering algorithm has been attached to SARTA to create cloudy radiances. We use 7377 ECMWF forecast profiles that are matched to AIRS field of views (FOVs) to test the three algorithms' cloudy radiances. An optimal estimation retrieval tests the fidelity of the RTA's Jacobian and radiance production by matching retrieved temperature and moisture profiles to the ECMWF forecast. Due to a collocation mismatch between the prescribed ECMWF cloud state and the AIRS FOV, we examine PDF's of the certain channels compared to AIRS, and the retrieved geophysical profiles compared to the ECMWF forecast.