Eta model forecasts over South America with improved land-surface processes representation

.The Centro de Previsao de Tempo e Estudos Climaticos (CPTEC) in Brazil has been running operationally the regional Eta model and producing 60-hour forecasts over South America on a twice-a-day basis. The forecasts have been satisfactory but some deficiency in the near surface variables has been noticed. A crude treatment of the land-surface processes based on the Bucket scheme may be responsible in part for the deficiencies. In this study another version of the model with the CAPS scheme, which contains vegetation and soil properties, is evaluated and compared for short-term forecasts. The model is run with NCEP analyses as initial conditions, and CPTEC/COLA global model forecasts as lateral boundary conditions. Model resolution is 40 km and 38 layers and had the top raised to 25 mb. The new scheme has 12 vegetation types and two soil layers. Short-term forecasts produced during one transition season are evaluated based on statistical scores, such as equitable threat scores of precipitation, root mean square error and forecast bias of temperature, humidity and wind. These scores are calculated for different forecast lead times, and 4 different sectors of the domain. Two case studies are also shown to illustrate the predicted fields during tropical convection in the Amazon region and a cold frontal passage in the Southeastern part of the continent. These cases are validated with surface observations