Publicações

The role of ocean-atmosphere interactions on summer rainfall over the South Atlantic Ocean is explored through the use of coupled ocean-atmosphere models. The Brazilian Center for Weather Forecast and Climate Studies (CPTEC) coupled ocean-atmosphere general circulation model (CGCM) and its atmospheric general circulation model (AGCM) are used to gauge the role of coupled modes of variability of the climate system over the South Atlantic on seasonal timescales. Twenty six years of summer (DJF) simulations were done in ensemble mode with the CGCM, and the AGCM forced with both observed sea surface temperature (SST) and the SST generated by the CGCM forecasts to investigate the dynamics/thermodynamics of the two major convergence zones in the Tropical Atlantic; the Intertropical Convergence Zone (ITCZ) and the South Atlantic Convergence Zone (SACZ). The results present both numerical model and observational evidence supporting the hypothesis that the ITCZ is a thermally direct, SST driven atmospheric circulation, while the SACZ is a thermally indirect atmospheric circulation controlling SST variability underneath-a consequence of ocean-atmosphere interactions not captured by the atmospheric model forced by prescribed ocean temperatures. Six CGCM model results of the ENSEMBLES project, NCEP/NCAR reanalysis data, and ocean and atmospheric data from buoys of the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) Project over the tropical Atlantic are used to validate the CPTECs coupled and uncoupled models simulations.

The Solar and Wind Energy Resource Assessment (SWERA) database is used to prepare and discuss scenarios for solar thermal applications in Brazil. The paper discusses low temperature applications (small and large scale water heating) and solar power plants for electricity production (concentrated solar power plants and solar chimney plants) in Brazil. The results demonstrate the feasibility of large-scale application of solar energy for water heating and electricity generation in Brazil. Payback periods for water heating systems are typically below 4 years if they were used to replace residential electric showerheads in low-income families. Large-scale water heating systems also present high feasibility and many commercial companies are adopting this technology to reduce operational costs. The best sites to set up CSP plants are in the Brazilian semi-arid region where the annual energy achieves 2.2 MW h/m2 and averages of daily solar irradiation are larger than 5.0 kW h/m2/day. The western area of Brazilian Northeastern region meets all technical requirements to exploit solar thermal energy for electricity generation based on solar chimney technology.

Three sections of the Asu catchment, which is located within the Cuieiras Reservation 80 km northwest of Manaus in Central Amazonia, Brazil, were gauged to create nested catchments of the first (0.95 km2), second (6.58 km2) and third (12.43 km2) Strahler orders. As the Cuieiras reserve contains pristine tropical rainforest, hydrological data collected in these catchments offers an opportunity to test the Distributed Hydrology Soil Vegetation Models (DHSVM) ability to simulate hydrological responses, and to represent the spatial distribution of hydrological phenomena such as evapotranspiration, soil moisture and water table depth. Digital Elevation Model (DEM) data were obtained from the Shuttle Radar Topography Mission (SRTM) data. We used a novel approach to produce high resolution (30 m) soil and vegetation maps that enabled a representative set of relevant parameters to be acquired. These soil and vegetation maps were derived from a hydrologically normalized DEM through the HAND (Height Above the Nearest Drainage) technique, a new type of terrain model procedure. The DHSVM model was calibrated and validated using the second order watershed. To test the models ability to represent processes at different spatial scales, the parameter set derived from the calibration was used to simulate the discharge of the first and third order streams. Model simulations of soil moisture, groundwater levels and discharge were compared with observed data and exhibited satisfactory performance overall, with the exceptions of the predicted water table depth and the underestimation of peak flows during the wet season. The results from these DHSVM runs indicate that the model is applicable to tropical forests environments (equatorial climates, lowland watersheds with deep soil), which are quite distinct from the environments for which the model was developed (temperate climates, mountainous watersheds with shallow soil). The study also demonstrated that the HAND terrain model is a useful tool for representing the spatial distributions of key hydrological parameters.

Historical simulations (present climate) and projections under RCP8.5 scenario (future climate) by HadGEM2-ES of temperature and precipitation are analyzed during the four seasons in South America. Projections of precipitation are discussed in terms of atmospheric circulation. The South Atlantic Convergence Zone (SACZ) and the Pacific South America (PSA) patterns are analyzed in simulations of present climate and in future climate projections. The model shows small systematic errors over South America, larger close to the northern South American coast in DJF and MAM. The seasonal variability of precipitation, temperature and wind fields is very well reproduced, mainly the summer/winter differences. The SACZ and the Intertropical Convergence Zone (ITCZ) are well simulated. The good model performance to reproduce the precipitation, temperature and wind fields, in the present climate, gives confidence in the projection results subject to the future scenarios. Changes from the present time to the future indicate increased precipitation over southern and southeastern Brazil and areas nearby and the tropical western South American coast. Reduced precipitation is projected over eastern Amazonia, northern South America and southern Chile. The changes are related to changes in the low level wind flow over the tropical North Atlantic, which reduces the advection of moisture to the continent and also to the increased low level flow over central South America southwards, which increases the humidity in the southern regions. The upper level flow changes are also consistent with the precipitation changes. There is a weakening of the Bolivian High and a strengthening of the subtropical jet over the continent. The SACZ dipole pattern is well simulated and in the future projections the southern center anomalies are more intense than in the present time. The PSA1 and PSA2 patterns are well represented in the present climate, but in the future projection only one dominant mode is identified as the typical teleconnection over the Pacific and South America.

One of the most interesting attributes of Lightning Location Systems (LLSs) data is that they can be analyzed in several ways according to the objectives of the study. However, the quality of the data is governed by the system performance and has some limitations when analyzed at different temporal/spatial scales, and these limitations will depend on the analysis method. This work focuses on approaches to minimize the variations associated with LLS performance. On this way, specific network configurations for the Brazilian Lightning Detection Network (BLDN) were obtained through the reprocessing of selected sensor data, resulting in three distinct datasets. Each dataset was then evaluated using different procedures: trimmed flash (exclusion of low-current discharges), thunderstorm days (TDs), and thunderstorm hours (THs). The comparison between TDs obtained from the LLS and TDs available from surface stations shows consistent results, with a good correlation of those datasets. An analysis of 11 years of BLDN data show also that improvement (over time) of the system sensitivity has led to the detection of an increasing number of low peak current events. By eliminating low peak current discharges (less than 19kA), the sensitivity variation was significantly reduced, partially normalizing long-term performance. TDs and THs were the most effective method to normalize temporal variations of the lightning activity, overcoming most of the network performance variations. From the spatial perspective, TDs and THs also seem to produce the most reliable lightning distribution. These results might guide long-term temporal and spatial analysis of lightning data, providing a more stable approach that is independent of system performance.

The Amazon represents one of the most biodiverse regions in the world, much of which is poorly known and highly threatened by conversion to agriculture. Because of the low capacity in the region to conduct science, conduct conservation planning, and enforce laws and regulations, it is also at high risk. Global climate change is exacerbating local land-use impacts that are affecting the regions climate on a landscape scale. For the unique climate and functioning system of the Amazon to persist in the future, halting forest loss is imperative, or the thermal and water balances largely creating the unique landscape will collapse.

The question that motivated us to write this chapter was How does hydroelectricity production contribute to the global emissions of greenhouse gases?. Here, we present an overview of (i) scientific advances on the topic and (ii) aspects of hydroelectric reservoir ecology in the context of greenhouse gas production, consumption and emission.