Publicações

This paper assesses the uncertainties involved in the projections of seasonal temperature and precipitation changes over South America in the twenty-first century. Climate simulations generated by 24 general circulation models are weighted according to the reliability ensemble averaging (REA) approach. The results show that the REA mean temperature change is slightly smaller over South America compared to the simple ensemble mean. Higher reliability in the temperature projections is found over the La Plata basin, and a larger uncertainty range is located in the Amazon. A temperature increase exceeding 2 °C is found to have a very likely (>90 %) probability of occurrence for the entire South American continent in all seasons, and a more likely than not (>50 %) probability of exceeding 4 °C by the end of this century is found over northwest South America, the Amazon Basin, and Northeast Brazil. For precipitation, the projected changes have the same magnitude as the uncertainty range and are comparable to natural variability.

This article presents research results of an extensible visualization pipeline for real-time exploratory analysis of spatially explicit simulations. We identify software requirements and discuss the main conceptual and design issues. We propose a protocol for data serialization, a high performance monitoring mechanism, and graphical interfaces for visualization. Performance experiments show that combining multithreading and the Blackboard design pattern reduces the visualization response time by 80%, with no significant increase in memory consumption (less than 7%). The components presented in this article have been integrated in the TerraME modeling platform for simulation of terrestrial systems.

In this report thunderstorm day monthly records obtained in three cities of southeast Brazil (SAo Paulo, Campinas, and Rio de Janeiro) since the 19th century are analyzed. The analysis is complemented by the spatial distribution of lightning in the last decade. For São Paulo and Campinas, data indicate a significant increase in thunderstorm activity during the period from the end of the 19th century to the present, simultaneously to an increase in the surface temperature well correlated to the population growth of the cities. This result did not match anything expected from natural climate cycles and gives strong observational evidence for the anthropogenic influence on the thunderstorm activity. For Rio de Janeiro, data did not show a significant positive trend from the middle of the 19th century to the present in spite of the increase in the surface temperature, suggesting that variations are most probably a result of a complex combination of local and large-scale features. In addition, a statistical analysis of the data after 1951 shows that a significant increase (by a factor of 3.7) in the thunderstorm activity in Rio de Janeiro occurs for the simultaneous occurrence of a positive anomaly of the South Atlantic sea surface temperature and La Nina, compared to the simultaneous occurrence of a negative anomaly and El Nino, even though no significant variation was found when each large-scale phenomena occurs isolated. The same occurs for São Paulo and Campinas, although with a lower amplitude.

The goal of this article is to investigate the influence of solar activity on thunderstorm activity in Brazil. For this purpose, thunder day data from seven cities in Brazil from 1951 to 2009 are analyzed with the wavelet method for the first time. To identify the 11-year solar cycle in thunder day data, a new quantity is defined. It is named TD1 and represents the power in 1-year in a wavelet spectrum of monthly thunder day data. The wavelet analysis of TD1 values shows more clear the 11-year periodicity than when it is applied directly to annual thunder day data, as it has been normally investigated in the literature. The use of this new quantity is shown to enhance the capability to identify the 11-year periodicity in thunderstorm data. Wavelet analysis of TD1 indicates that six out seven cities investigated exhibit periodicities near 11 years, three of them significant at a 1% significance level (p<0.01). Furthermore, wavelet coherence analysis demonstrated that the 11-year periodicity of TD1 and solar activity are correlated with an anti-phase behavior, three of them (the same cities with periodicities with 1% significance level) significant at a 5% significance level (p<0.05). The results are compared with those obtained from the same data set but using annual thunder day data. Finally, the results are compared with previous results obtained for other regions and a discussion about possible mechanisms to explain them is done. The existence of periodicities around 11 years in six out of seven cities and their anti-phase behavior with respect to 11-year solar cycle suggest a global mechanism probably related to a solar magnetic shielding effect acting on galactic cosmic rays as an explanation for the relationship of thunderstorm and solar activity, although more studies are necessary to clarify its physical origin.

The Upward Lightning Triggering Study (UPLIGHTS) is a three-year National Science Foundation-funded field project that is taking place in Rapid City, South Dakota, from April 2012 to September 2014. Three upward flashes that occurred within a 20-min period were all triggered by a preceding +CG (cloud-to-ground) flash. In each case, in-cloud brightening following the +CG propagated toward the towers prior to upward leader initiation. Supporting electric-field data suggested that the approaching in-cloud brightening was horizontally propagating negative-leader development occurring during the +CG continuing current, and that the electric-field change created by the approaching negative leaders caused the initiation of upward positive leaders from the towers. Although none of the 10 towers had current sensing instrumentation, it is likely that a large majority of the upward flashes were upward negative lightning. The research may result in improved detection of upward lightning by lightning location systems.

A ideia de sustentabilidade na empresa indica que, para alcançar um bom desempenho econômico, as empresas devem adotar uma estratégia que contemple o conceito triple bottom line, segundo o qual, as empresas devem prestar contas de sua performance nas áreas econômica, ambiental e social. O presente trabalho tem por objetivo descrever os benefícios de colocar a sustentabilidade no cerne da Governança Corporativa, como estratégia empresarial que gera valor a partir da busca de melhores resultados sociais e ambientais. Menciona-se o exemplo da empresa Masisa para analisar a implementação Triple Bottom Line e a Governança Corporativa em dois países que a empresa atua, Brasil e Chile.

How tropical forest carbon stocks might alter in response to changes in climate and atmospheric composition is uncertain. However, assessing potential future carbon loss from tropical forests is important for evaluating the efficacy of programmes for reducing emissions from deforestation and degradation. Uncertainties are associated with different carbon stock responses in models with different representations of vegetation processes on the one hand, and differences in projected changes in temperature and precipitation patterns on the other hand. Here we present a systematic exploration of these sources of uncertainty, along with uncertainty arising from different emissions scenarios for all three main tropical forest regions: the Americas (that is, Amazonia and Central America), Africa and Asia. Using simulations with 22 climate models and the MOSES-TRIFFID land surface scheme, we find that only in one of the simulations are tropical forests projected to lose biomass by the end of the twenty-first century – and then only for the Americas. When comparing with alternative models of plant physiological processes, we find that the largest uncertainties are associated with plant physiological responses, and then with future emissions scenarios. Uncertainties from differences in the climate projections are significantly smaller. Despite the considerable uncertainties, we conclude that there is evidence of forest resilience for all three regions.

How tropical forest carbon stocks might alter in response to changes in climate and atmospheric composition is uncertain. However, assessing potential future carbon loss from tropical forests is important for evaluating the efficacy of programmes for reducing emissions from deforestation and degradation. Uncertainties are associated with different carbon stock responses in models with different representations of vegetation processes on the one hand, and differences in projected changes in temperature and precipitation patterns on the other hand. Here we present a systematic exploration of these sources of uncertainty, along with uncertainty arising from different emissions scenarios for all three main tropical forest regions: the Americas (that is, Amazonia and Central America), Africa and Asia. Using simulations with 22 climate models and the MOSES-TRIFFID land surface scheme, we find that only in one of the simulations are tropical forests projected to lose biomass by the end of the twenty-first century – and then only for the Americas. When comparing with alternative models of plant physiological processes, we find that the largest uncertainties are associated with plant physiological responses, and then with future emissions scenarios. Uncertainties from differences in the climate projections are significantly smaller. Despite the considerable uncertainties, we conclude that there is evidence of forest resilience for all three regions.

It is well known that most of the severe droughts in Amazonia, such as that of 1997, are El Nio-related. However, in 2005, the Amazon was affected by a severe drought that was not El Nio-related, as most of the rainfall anomalies that have happened in southwestern Amazonia are driven by sea surface temperature anomalies in the tropical North Atlantic. Earlier studies have analyzed both droughts in terms of their meteorological causes and impacts in terra firme (non-flooded) forests. This study compares the hydrological effects of both droughts on the Amazonian floodplain and discusses their potential ecological and human impacts based on an extensive literature review. The results revealed that the effects of the 2005 drought were exacerbated because rainfall was lower and evaporation rates were higher at the peak of the dry season compared to the 1997 drought. This induced a more acute depletion of water levels in floodplain lakes and was most likely associated with higher fish mortality rates. Based on the fact that the stem growth of many floodplain species is related to the length of the non-flooded period, it is hypothesized that the 1997 drought had more positive effects on floodplain forest growth than the 2005 drought. The fishing community of Silves in central Amazonia considered both droughts to have been equally severe. However, the 2005 drought was widely broadcasted by the press; therefore, the governmental mitigation efforts were more comprehensive. It is suggested that the availability of new communication technology and greater public awareness regarding environmental issues, combined with the new legal framework for assessing the severity of calamities in Brazil, are among the primary factors that explain the difference in societal response between the two droughts.

Positive flashes correspond to approximately only 10\% of the total number of flashes produced by a thunderstorm. However, strokes with high peak currents and long continuing currents are usually present in positive flashes. Therefore, positive flashes are responsible for more intense damage than the negative ones. Positive flashes often are preceded by significant and long duration intracloud (IC) discharge activity. We observe in detail the electric field variations produced by 80 cloud-to-ground lightning flashes in 9 different storms in S. Paulo, Brazil during the summers of 2009-2011. Intracloud discharges preceding the positive cloud-to-ground flashes and some characteristics of the electric field changes produced by the return stroke that occurred at ranges of 3-80 km from the site of the electric field measurements were analyzed. All flashes presented breakdown pulses prior to the return stroke. The mean time interval between the preliminary breakdown pulse (PBP) and return stroke was 157 ms. The pulse train duration have a mean value of 3.1 ms. Only 6 out of 80 cases analyzed did not present pulse trains but only one single bipolar breakdown pulse before the return stroke. In 95\% of cases the initial breakdown pulse presented the same initial polarity of the succeeding return stroke. Time interval between pulses in a pulse train had a mean value of 280 mu s. The mean values of pulse width is 25.2 mu s. The mean values of zero-to-peak risetimes and of the 10-90\% risetimes for 72 return strokes electric field waveforms are 9.5 and 5.7 mu s respectively. The AM value of peak amplitudes of the positive return strokes fields normalized to 100 km is 17.0 V/m.

Brazils wind energy production has escalated up recently. However, the long-term wind projects do not include the yet unknown impacts of climate changes on wind power. This work is an assessment of these impacts by applying forecasts of a climate model and trend analysis over climatological time series from selected ground sites. Findings indicate a favourable scenario for wind power exploitation in Brazil on the long run.