The objective of this study is to assess the climate projections over South America using the Eta-CPTEC regional model driven by four members of an ensemble of the Met Office Hadley Centre Global Coupled climate model HadCM3. The global model ensemble was run over the twenty-first century according to the SRES A1B emissions scenario, but with each member having a different climate sensitivity. The four members selected to drive the Eta-CPTEC model span the sensitivity range in the global model ensemble. The Eta-CPTEC model nested in these lateral boundary conditions was configured with a 40-km grid size and was run over

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To provide long-term simulations of climate change at higher resolution, Regional Climate Models (RCMs) are nested in global climate models (GCMs). The objective of this work is to evaluate the Eta RCM simulations driven by three global models, the HadGEM2-ES, BESM, and MIROC5, for the present period, 1961-1990. The RCM domain covers South America, Central America, and Caribbean. These simulations will be used for assessment of climate change projections in the region. 439Eta Model

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Upgrades implemented over a number of years in an open source version of the Eta model, posted at the CPTEC web site http://etamodel.cptec.inpe.br/, are summarized and examples of benefits are shown. The version originates from the NCEP's Workstation Eta code posted on the NCEP web site http://www.emc.ncep.noaa.gov/ mmb/wrkstn_eta, which differs from the NCEP's latest operational Eta by having the WRF-NMM nonhydrostatic option included. Most of the upgrades made resulted from attention paid to less than satisfactory performance noted in several Eta results, and identification of the reasons for the problem. Others came from simple expectation that including a feature that is physically justified but is missing in the code should help. The most notable of the upgrades are the introduction of the so-called sloping steps, or discretized shaved cells topography; piecewise-linear finitevolume vertical advection of dynamic variables; vapor and hydrometeor loading in the hydrostatic equation, and changes aimed at refining the convection schemes available in the Eta. Several other modifications have to do with the calculation of exchange coefficients, conservation in the vertical diffusion, and diagnostic calculation of 10-m winds. Several examples showing improved performance resulting from the dynamics changes are given. One includes a case of unrealistically low temperatures in several mountain basins generated by a centered vertical advection difference scheme's unphysical advection from below ground, removed by its replacement with a finitevolume scheme. Another is that of increased katabatic winds in the Terra Nova Bay Antarctica region. Successful forecast of the severe downslope zonda wind case in the lee of the highest peaks of the Andes is also shown, and some of the recent successful verification results of the use of the upgraded model are pointed out. The code is used at numerous places, and along with setup information it is available for outside users at the CPTEC Eta web site given above.

Abstract. Seasonal forecasts run by the Eta Model over South America were evaluated with respect to precipitation predictability at different time scales, seasonal, monthly and weekly for one-year period runs. The model domain was configured over most of South America in 40 km horizontal resolution and 38 layers. The lateral boundary conditions were taken from CPTEC GCM forecasts at T62L28. The sea surface temperature was updated daily with persisted anomaly during the integrations. The total time integration length was 4.5 months. The Eta seasonal forecasts represented reasonably well the large scale precipitation systems over South America such as the Intertropical Convergence Zone and the South Atlantic Convergence Zone. The total amounts were comparable to observations. The season total precipitation forecasts from the driver model exhibited large overestimate. In general, the largest precipitation errors were found in ASON season and the smallest in FMAM. The major error areas were located along the northern and northeastern coast and over the Andes. These areas were present in both models. The monthly precipitation totals indicated that the intra-seasonal variability, such as the monsoonal onset, was reasonably captured by the model. The equitable threat score and the bias score showed that the Eta Model forecasts had higher precipitation predictability over the Amazon Region and lower over Northeast Brazil. The evaluation of the precipitation forecast range showed that at the fourth month the forecast skill was still comparable to the first month of integration. Comparisons with the CPTEC GCM forecasts showed that the Eta improved considerably the forecasts from the driver model. Five-member ensemble runs were produced for the NDJF rainy season. Both driver model and Eta Model forecasts showed some internal variability in the SACZ and over the Andes regions. Comparison of the Eta Model seasonal forecasts against climatology showed that in general the model produced additional useful information over the climatology. Transient variabilCorrespondence to: S. C. Chou (chou@cptec.inpe.br) ity was evaluated by tracking the frontal passages along the eastern coast. The frontal timing was no longer captured by the model but some indication of the frequency and of the northward movement was given by the model forecast. Weekly precipitation totals were evaluated for the São Francisco Basin. Some parameters, such as the mean and the standard deviation of the 7-day total precipitation, were comparable to observations. The correlations between the forecast and the observed 7-day series were positive, but low.

Ten-year seasonal climate reforecasts over South America are obtained using the Eta Regional Climate Model at 40 km resolution, driven by the large-scale forcing from the global atmospheric model of the Center for Weather Forecasts and Climate Studies. The objective of this work is to evaluate these regional reforecasts. The dataset is comprised of four-month seasonal forecasts performed on a monthly basis between 2001 and 2010. An ensemble of fi ve members is constructed from fi ve slightly different initial conditions to partially reduce the uncertainty in the seasonal forecasts. The seasonal mean precipitation and 2-meter temperature forecasts are compared with the observations. The comparison shows that, in general, forecasted precipitation is underestimated in the central part of the continent in the austral summer, whereas the forecasted 2 meter temperature is underestimated in most parts of the continent and throughout the year. Skill scores show higher skill in the northern part of the continent and lower skill in the southern part of the continent, but mixed skill signs are seen in the central part of the continent. During the El Niño and La Niña seasons, the forecast skill scores clearly increase. The downscaling of the Eta model seasonal forecasts provides added value over the driver global model forecasts, especially during rainy periods.

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