On the Extension of Rapid Radiative Transfer Model to the Shortwave Region

In this work we describe the second phase in the development of the rapid radiative transfer model (RRTM) (Mlawer et al. 1996), a rapid and accurate radiative transfer model designed for climate applications. The initial phase of RRTM, which uses the correlated-k method for radiative transfer, allowed the calculation of fluxes and cooling rates in the longwave region in clear-sky conditions. Results from this method have been verified by validations performed using the line-by-line radiative transfer model (LBLRTM) (Clough et al. 1992; Clough and Iacono 1995) for atmospheric profiles spanning a wide range of conditions. The accuracy of LBLRTM, which provides the absorption coefficients for the k-distributions used by RRTM, has been established, in turn, by extensive high-resolution validations with measurements, particularly those performed in the long-wave region as part of the Atmospheric Radiation Measurement (ARM) program (Brown et al. 1996). These validations provide a traceable link from RRTM to observations done at high spectral resolution.