Validation of the coupled Eta/SSiB model over South America

Two 1-month integrations were performed with the regional Eta model coupled with the Simplified Simple Biosphere model (SSiB) over South America. The goal of the present work is to validate the model and to investigate its biases and skill on the simulations of South American climate. This is an initial step on the use of this model for climate research. The Eta model was set up with 80-km horizontal resolution and 38 vertical layers over the South American continent and part of the adjacent oceans. Analyses from the National Centers for Environmental Prediction (NCEP) were used as initial and lateral boundary conditions. The selected months were August and November 1997, which are in opposite phases of the precipitation annual cycle observed in the central part of South America. The model was integrated continuously for each 1-month period. Monthly means and daily variations of simulated precipitation and surface temperature compare well with observations. The patterns of simulated outgoing longwave radiation are also similar to the observed ones. However, a positive bias is verified in the simulations. The model shows a positive bias in latent and sensible heat surface fluxes due to an excessive shortwave incoming radiation at the surface. Comparisons with a version of the Eta model coupled with the bucket model shows that the Eta/SSiB version improves the surface temperature and increases precipitation in the interior of the continent during wet months.