Eta model simulations using two radiation schemes in clear-sky conditions

This work evaluates the performance of two radiation parameterization schemes in 30-day clear-sky runs of the Eta model over a region in Southeast Brazil. Two versions of the Eta model are compared: a version using the radiation scheme developed by the Geophysical Fluid Dynamics Laboratory (GFDL) and a recently developed version using the Rapid Radiative Transfer Model for GCM (RRTMG). These simulations are compared against CMSAF satellite data and surface station data. The simulation using RRTMG produced downward surface shortwave radiation fluxes closer to observations and reduced the systematic positive bias of the Eta simulation using the GFDL scheme. The 2-m temperature negative bias found in the Eta-GFDL simulations is reduced in the Eta-RRTMG simulations, which results from a larger net total radiation in the Eta-RRTMG simulations. The new version has better accuracy than the Eta using the GFDL scheme for most of the evaluated variables, particularly for clear-sky conditions.