Publicações

Sugarcane is a typical culture of hot and humid climate and therefore is well adapted to the climate in many regions of Brazil. However, there may be yield reductions in the Northeastern region of Brazil due to possible future reductions in rainfall levels. The aim of this study was to simulate, using the Century 4.5 model, the impact of climate changes on potential sugarcane yield in Goiana and Itambé, Zona da Mata of Pernambuco. The Century 4.5 model was booted with soil and climate data from 1950 to 2012. Data on total soil carbon, soil texture (sand, silt and clay contents), pH, soil density and soc stocks were obtained from previous studies. The climate scenario used was the average emissions SRES A1B, designed by Eta/CPTEC model for periods 20142040, 20412070 and 20712100, which is composed of LOW member (low emissions) and HIGH member (high emissions). According to the results obtained by A1B scenario, the potential yield can be reduced in the near future (20142040). The high temperatures in northeastern Brazil will increase the evapotranspiration rates, reducing the amount of water available in the soil, making the planting of sugarcane increasingly difficult, which tend to be strongly reduced in drier areas, such as cities located in the western portion of the Zona da Mata region, northern state of Pernambuco, Brazil.

We present a new segmentation method called Weighted Felzenszwalb and Hutten-locher method (WFH), an improved version of the well-known graph-based segmentation method, Felzenszwalb and Huttenlocher method (FH). Our method uses a non-linear discrimination function based on Polynomial Mahalanobis Distance (PMD) as the color similarity metric. Two empirical validation experiments were performed using as a golden standard ground truths from a publicly available source, the Berkeley dataset, and an objective segmentation quality measure, the Rand dissimilarity index. In the first experiment the results were compared against the original FH method. In the second, WFH was compared against several well-known segmentation methods. In both cases WFH presented significant better similarity results when compared with the golden standard and segmentation results presented a reduction of over-segmented regions.

Urbanization and land use changes alter the nitrogen (N) cycle, with critical consequences for continental freshwater resources, coastal zones, and human health. Sewage and poor watershed management lead to impoverishment of inland water resources and degradation of coastal zones. Here we review the N contents of rivers of the three most important watersheds in South America: the Amazon, La Plata, and Orinoco basins. To evaluate potential impacts on coastal zones, we also present data on small- and medium-sized Venezuelan watersheds that drain into the Caribbean Sea and are impacted by anthropogenic activities. Median concentrations of total dissolved nitrogen (TDN) were 325 μg L-1 and 275 μg L-1 in the Amazon and Orinoco basins, respectively, increasing to nearly 850 μg L-1 in La Plata Basin rivers and 2000 μg L-1 in small northern Venezuelan watersheds. The median TDN yield of Amazon Basin rivers (approximately 4 kg ha-1 yr-1) was larger than TDN yields of undisturbed rivers of the La Plata and Orinoco basins; however, TDN yields of polluted rivers were much higher than those of the Amazon and Orinoco rivers. Organic matter loads from natural and anthropogenic sources in rivers of South America strongly influence the N dynamics of this region.

In this report monthly thunderstorm days (TD) in 14 large cities of Brazil from 1951 to 2010 are compared with data obtained in the first part of the 20th century in the same cities and correlated with sea surface temperature (SST) of the equatorial Pacific Ocean and Tropical Atlantic Ocean. On average over all cities, 77 TD are reported each year after 1951, against 43 TD in the first part of the 20th century, an increase of 79%. The increase seems to be related to increase in the urbanization in these cities, and not to global warming. A comparative analysis of TD for the whole country with El Niño-Southern Oscillation (ENSO) events suggests that the tendency for El Niño to increase the thunderstorm activity is evident in the South (only in the Spring/Summer), Southeast, Northeast and North (only in the Fall/Winter) regions. Regarding the Tropical Atlantic Ocean SST, a similar analysis using the Tropical South Atlantic (TSA) and Tropical North Atlantic (TNA) indices suggests that no significant differences exist between the thunderstorm activity for the two extreme positive and negative TSA conditions in the South and Southeast regions, while in the Northeast and North regions there is a significant increase in the thunderstorm activity during extreme positive TSA. Differently, only in the Northeast region there is a significant influence of TNA on thunderstorm activity. The influence is such that the thunderstorm activity is larger for the extreme negative TNA than for extreme positive TNA. All significant changes were quantified and significant variations were observed. For all parameters investigated (ENSO, TSA and TNA) the Northeast region showed the most significant changes.

Environmental scenarios were largely exploratory in the past decades. Normative approaches gradually became more popular and more widely applied over the last decade, due to the rising popularity of the strongly normative concept of sustainability. Here we present a normative scenario approach conceived to promote the discussion about a sustainable future in heterogeneous and conflicting regions such as the Brazilian Amazon. We present a synthesis of the scenario process and the two case studies. The first case study was developed on an agro-extrativist settlement project. Then, we successfully reproduced the method to the whole Brazilian Amazon, involving representatives of civil society organizations, productive sector and government. The normative scenario approach we adopted here was conceived as a tool to subsidize a broader discussion about the future we want and how to get there – acknowledging that current society decisions will strongly influence the future.

The study aims to analyze the spectral behavior of leaves of Eucalyptus globulus attacked in four different severity levels by Mycosphaerella spp. in different positions in the canopy of the tree in the four seasons, considering two regions of the electromagnetic spectrum: visible and near infrared. The plant material was collected in all seasons, in different positions in the tree (base, middle and top of the canopy extract). In the laboratory, leaves were classified into four levels of severity (healthy, little, medium and heavy fire) and then made measurements of spectral reflectance measured with a spectroradiometer. The spectral behavior of Eucalyptus globules leaves is characteristic according to the severity degree of the disease, differing primarily in the other high levels of infection by Mycosphaerella spp. and differ mainly of healthy leaves and leaves which are little attacked, in both regions of the electromagnetic spectrum, this behavior occurs for different treetop positions and climate seasons, varying the amount of reflected energy. It is concluded that the reflectance of the Eucalyptus globules leaves attacked by Mycosphaerella spp. differs according to the position in the tree crown and the weather station when they were collected and to the advanced levels of disease severity.

The proliferation of digital cameras co-located with eddy covariance instrumentation provides new opportunities to better understand the relationship between canopy phenology and the seasonality of canopy photosynthesis. In this paper we analyze the abilities and limitations of canopy color metrics measured by digital repeat photography to track seasonal canopy development and photosynthesis, determine phenological transition dates, and estimate intra-annual and interannual variability in canopy photosynthesis. We used 59 site-years of camera imagery and net ecosystem exchange measurements from 17 towers spanning three plant functional types (deciduous broadleaf forest, evergreen needleleaf forest, and grassland/crops) to derive color indices and estimate gross primary productivity (GPP). GPP was strongly correlated with greenness derived from camera imagery in all three plant functional types. Specifically, the beginning of the photosynthetic period in deciduous broadleaf forest and grassland/crops and the end of the photosynthetic period in grassland/crops were both correlated with changes in greenness; changes in redness were correlated with the end of the photosynthetic period in deciduous broadleaf forest. However, it was not possible to accurately identify the beginning or ending of the photosynthetic period using camera greenness in evergreen needleleaf forest. At deciduous broadleaf sites, anomalies in integrated greenness and total GPP were significantly correlated up to 60 days after the mean onset date for the start of spring. More generally, results from this work demonstrate that digital repeat photography can be used to quantify both the duration of the photosynthetically active period as well as total GPP in deciduous broadleaf forest and grassland/crops, but that new and different approaches are required before comparable results can be achieved in evergreen needleleaf forest.

The progress from the last four years in solar energy resource assessment for Chile is reported, including measurements from a ground station network spanning from two to three years of data, and satellite estimations from the recently developed Chile-SR model including two full years of data. The model introduces different procedures for the meteorological variables and the effective cloud cover computations that allow estimation of the global horizontal and diffuse irradiation on an hourly basis. Direct normal irradiation is computed by applying proper solar geometry corrections to the direct horizontal irradiation. The satellite estimation model was developed as an adaptation from Brazil-SR model, with an improved formulation for altitude-corrected atmospheric parameters, and a novel formulation for calculating effective cloud covers while at the same time detecting and differentiating it from snow covers and salt lakes. The model is validated by comparison with ground station data. The results indicate that there are high radiation levels throughout the country. In particular, northern Chile is endowed with one of the highest solar resources in the world.

Extreme rainfall events can be considered a natural manifestation of the environment in which they are embedded and foreknowledge about their future behavior is very important, especially for decision makers. In this context, we aimed to explore the future behavior of extreme rainfall intensity through numerical simulations with the ETA model. The model was forced with a scenario of high greenhouse gas emissions for the middle of the 21st Century as described for A1B emission scenario. We detailed the main changes in accumulated rainfall produced by heavy events, very heavy events and rare events over a broad area of South America with a focus on the tropical sector. The methodology applied here is capable of separating extreme events and establishing the quantity of rainfall yielded by them. We have found that in the near future (2041-2050) rare events will tend to increase over the Amazon basin, followed by reductions in heavy and very heavy events. Conversely, heavy, very heavy and rare events are expected to decline over northeast Brazil. Furthermore, increases were found for heavy, very heavy and rare events over southern Brazil.

Changing climatic conditions have led to a significant increase in the magnitude and frequency of extreme rainfall events in the Central Andes of South America. These events are spatially extensive and often result in substantial natural hazards for population, economy and ecology. Here we develop a general framework to predict extreme events by introducing the concept of network divergence on directed networks derived from a non-linear synchronization measure. We apply our method to real-time satellite-derived rainfall data and predict more than 60% (90% during El Nino conditions) of rainfall events above the 99th percentile in the Central Andes. In addition to the societal benefits of predicting natural hazards, our study reveals a linkage between polar and tropical regimes as the responsible mechanism: the interplay of northward migrating frontal systems and a low-level wind channel from the western Amazon to the subtropics.

A global assessment of precipitation chemistry and deposition has been carried out under the direction of the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) Scientific Advisory Group for Precipitation Chemistry (SAG-PC). The assessment addressed three questions: (1) what do measurements and model estimates of precipitation chemistry and wet, dry and total deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity, and phosphorus show globally and regionally? (2) has the wet deposition of major ions changed since 2000 (and, where information and data are available, since 1990) and (3) what are the major gaps and uncertainties in our knowledge? To that end, regionally-representative measurements for two 3-year-averaging periods, 20002002 and 20052007, were compiled worldwide. Data from the 20002002 averaging period were combined with 2001 ensemble-mean modeling results from 21 global chemical transport models produced in Phase 1 of the Coordinated Model Studies Activities of the Task Force on Hemispheric Transport of Air Pollution (TF HTAP). The measurement data and modeling results were used to generate global and regional maps of major ion concentrations in precipitation and deposition. A major product of the assessment is a database of quality assured ion concentration and wet deposition data gathered from regional and national monitoring networks. The database is available for download from the World Data Centre for Precipitation Chemistry (http://wdcpc.org/). The assessment concludes that global concentrations and deposition of sulfur and nitrogen are reasonably well characterized with levels generally highest near emission sources and more than an order of magnitude lower in areas largely free of anthropogenic influences. In many parts of the world, wet deposition of reduced nitrogen exceeds that of oxidized nitrogen and is increasing. Sulfur and nitrogen concentrations and deposition in North America and Europe have declined significantly in line with emission reduction policies. Major regions of the world, including South America, the more remote areas of North America, much of Asia, Africa, Oceania, polar regions, and all of the oceans, are inadequately sampled for all of the major ions in wet and dry deposition, and particularly so for phosphorus, organic forms of nitrogen, and weak acids including carbonates and organic acids. Measurement-based inferential estimates of dry deposition are limited to sulfur and some nitrogen in only a few regions of the world and methods are highly uncertain. The assessment concludes with recommendations to address major gaps and uncertainties in global ion concentration and deposition measurements.