Extended range forecasts over South America using the regional eta model

An 80-km National Centers for Environmental Prediction eta model was configured to run over the South America continent. This limited area model has 38 layers in the atmosphere, and its domain includes part of the adjacent Atlantic and Pacific Oceans. The model was setup to perform 1 month forecasts. The version used in these preliminary experiments uses a bucket model to describe water in the ground and a modified Betts-Miller scheme for producing convective precipitation. The experiments used constant sea surface temperature held and initial soil moisture from climatology. Results obtained from a dry season month and a rainy season month over South America in 1997 show that the reinitialization of model at short range forecasts is not necessary as was done with the previous version of the model. These results show no obvious drying of the atmosphere or tendency with time of the domain average surface pressure. In both cases (dry and wet) the model seems to have reproduced the climatological signal of the forecast months. The monthly accumulated total precipitation agrees well with the observations. These runs showed that the current configuration of the eta model is stable and capable of producing continuous extended range runs over South America.