Validation of the RRTM Shortwave Radiation Model and Comparison to GCM Shortwave Models

An important step toward improving radiative transfer codes in general circulation models (GCMs) is to thoroughly evaluate them either by comparison to measurements directly or by comparing them to other data-validated radiation models. The Rapid Radiative Transfer Model (RRTM) shortwave (SW) radiation model accurately reproduces direct beam fluxes from the Line-by-Line Radiative Transfer Model (LBLRTM) (Clough and Iacono 1995), and direct and diffuse fluxes from Code for High-resolution Accelerated Radiative Transfer with Scattering (CHARTS); (Moncet and Clough 1997). All three models were developed at Atmospheric and Environmental Research, Inc. with support from the Atmospheric Radiation Measurement (ARM) Program. Shortwave clear-sky fluxes from two operational GCMs are evaluated by comparison to RRTM_SW for several standard profiles.