Validation of the community radiative transfer model

To enhance the capability of numerical weather predictions (NWP), accurate simulation of radiation at the top of the atmosphere is extremely important to the improvement of the quality of satellite radiance data assimilation under all weather conditions. In support of the US Joint Center for Satellite Data Assimilation (JCSDA) Community Radiative Transfer Model (CRTM), the bulk-scattering properties of ice clouds are developed using a set of updated ice particle single-scattering libraries. To validate the CRTM, a rigorous coupled model based on a combination of the discrete ordinate radiative transfer (DISORT) model and the line-by-line radiative transfer model (LBLRTM) is established as a standard model. The comparisons indicate that the CRTM is quite accurate for both clear sky and ice cloudy radiance simulations. By comparing the computer CPU run times, we find the CRTM is faster than DISORT by approximately two orders of magnitude. We also compared the Atmospheric Infrared Sounder (AIRS) radiances and the corresponding theoretical simulations from the CRTM based on the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products and AIRS atmospheric profiles as inputs.