Publicações

A cobertura vegetal da superfície continental tem sido consideravelmente alterada pelas atividades humanas, principalmente através da conversão em grande escala da vegetação natural por áreas de cultivos e pastagens. Essas mudanças na cobertura da superfície podem alterar o clima regional e global por meio de processos biofísicos e biogeoquímicos. Assim, o presente trabalho avaliou como a substituição da vegetação natural da caatinga por agropecuária, bem como a degradação da caatinga, podem causar modificações nos processos de superfície na região semiárida do Nordeste do Brasil (NEB), a qual é uma das mais vulneráveis do Brasil, do ponto de vista social, à mudança de clima. Para isto, foram realizados experimentos numéricos de conversão da cobertura da superfície utilizando-se o modelo Integrated Biosphere Simulator IBIS. Por meio da conversão da cobertura vegetal, as características morfológicas e biofísicas da vegetação foram modificadas e por isso, causaram alterações nas componentes dos balanços de energia, de água e de carbono. O balanço de energia foi mais afetado pelo aumento do albedo decorrente da alteração da vegetação caatinga para agropecuária e para caatinga degradada. Além disso, as alterações do comprimento de rugosidade e das propriedades estomáticas da vegetação corroboraram para as alterações ocorridas nas trocas turbulentas entre a superfície e a atmosfera. Com relação às componentes do balanço de carbono, durante a estação chuvosa com a conversão da caatinga natural para agropecuária, houve um aumento da assimilação de CO2 (NEE) e com isso maior Produtividade Primária Líquida do ecossistema (NPP). O contrário ocorreu com a conversão para caatinga degradada, na qual a assimilação se manteve próxima de zero durante as horas do dia e NPP foi reduzida, o que pode ter ocorrido em função das alterações ocorridas no Índice de Área Foliar (IAF), tanto para a agropecuária, como para a caatinga degradada.

GPS time synchronized high-speed video records (at 4000 frames per second) and electric field waveforms are discussed for one stepped leader of a negative cloud-to-ground flash whose initial development becomes visible above cloud base. The leader emerges from the opaque region of the thundercloud around 4800 m above ground, propagating with speeds of the order of 106 m s -1. It is possible to see that this early, bright, and fast propagation period occurred simultaneously with the emission of initial breakdown bipolar pulse trains. The leader gradually reduces its speed and luminous intensity: When its tip is less than 3000 m above the ground, the propagation speeds oscillate between 2 and 4 × 105 m s -1 until it makes contact approximately 16 ms after it first became visible. With time, the initial breakdown waveform is gradually replaced by unipolar pulses and the leader propagation speed drops to the 105 m s-1 range. Key Points Fast visible leader development during the initial breakdown pulse activity Breakdown bipolar pulse trains become unipolar as the leader slows down.

Dados termopluviométricos são utilizados em diversos estudos. Contudo, a escassez de dados resultante da baixa densidade de estações meteorológicas é um problema frequentemente encontrado. Com isto, a utilização de dados estimados por satélites tem-se mostrado importante para regiões nas quais eles são escassos. Neste trabalho foram realizadas comparações entre dados mensais de precipitação pluvial estimados pelo satélite TRMM e de temperatura, estimados pelo satélite Aqua/MODIS aos dados observados por estações de superfície, para diferentes localidades do Estado de São Paulo, no período de 2003 a 2010. Os resultados demonstraram que para os dados de precipitação pluvial os menores erros foram observados nos meses de inverno e os maiores nos meses de verão. Em relação aos dados de temperatura observou-se que, com a inclusão de um fator de correção, os dados do satélite Aqua apresentaram boa exatidão em todos os meses. De maneira geral, os resultados obtidos indicam que os satélites TRMM e Aqua são alternativas eficientes na aquisição de informações em locais onde há falhas ou escassez dos mesmos podendo ser também utilizados na análise da consistência de dados coletados por meio de redes meteorológicas.

In Brazil, most of the disasters involving landslide occur in coastal regions, with population density concentrated on steep slopes. Thus, different approaches have been used to evaluate the landslide risk, although the greatest difficulty is related to the scarcity of spatial data with good quality. In this context, four cities located on the southeast coast of Brazil Santos, Cubatão, Caraguatatuba and Ubatuba in a region with the rough reliefs of the Serra do Mar and with a history of natural disasters were evaluated. Spatial prediction by fuzzy gamma technique was used for the landslide susceptibility mapping, considering environmental variables from data and software in the public domain. To validate the susceptibility mapping results, it was overlapped with risk sectors provided by the Geological Survey of Brazil (CPRM). A positive correlation was observed between the classes most susceptible and the location of these sectors. The results were also analyzed from the categorization of risk levels provided by CPRM. To compare the approach with other studies using landslide-scar maps, correlated indexes were evaluated, which also showed satisfactory results, thus indicating that the methodology presented is appropriate for risk assessment in urban areas and can be replicated to municipalities that do not have risk areas mapped.

The coastal zone of northeastern Brazil is characterized by intense human activities and by large settlements and also experiences high soil losses that can contribute to environmental damage. Therefore, it is necessary to build an integrated modeling-forecasting system for rainfall-runoff erosion that assesses plans for water availability and sediment yield that can be conceived and implemented. In this work, we present an evaluation of an integrated modeling system for a basin located in this region with a relatively low predictability of seasonal rainfall and a small area (600km2). The National Center for Environmental Predictions – NCEP’s Regional Spectral Model (RSM) nested within the Center for Weather Forecasting and Climate Studies – CPTEC’s Atmospheric General Circulation Model (AGCM) were investigated in this study, and both are addressed in the simulation work. The rainfall analysis shows that: (1) the dynamic downscaling carried out by the regional RSM model approximates the frequency distribution of the daily observed data set although errors were detected in the magnitude and timing (anticipation of peaks, for example) at the daily scale, (2) an unbiased precipitation forecast seemed to be essential for use of the results in hydrological models, and (3) the information directly extracted from the global model may also be useful. The simulated runoff and reservoir-stored volumes are strongly linked to rainfall, and their estimation accuracy was significantly improved at the monthly scale, thus rendering the results useful for management purposes. The runoff-erosion forecasting displayed a large sediment yield that was consistent with the predicted rainfall.

We investigate the spatial characteristics of extreme rainfall synchronicity of the South American Monsoon System (SAMS) by means of Complex Networks (CN). By introducing a new combination of CN measures and interpreting it in a climatic context, we investigate climatic linkages and classify the spatial characteristics of extreme rainfall synchronicity. Although our approach is based on only one variable (rainfall), it reveals the most important features of the SAMS, such as the main moisture pathways, areas with frequent development of Mesoscale Convective Systems (MCS), and the major convergence zones. In addition, our results reveal substantial differences between the spatial structures of rainfall synchronicity above the 90th and above the 95th percentiles. Most notably, events above the 95th percentile contribute stronger to MCS in the La Plata Basin. Key Points Complex Networks of rainfall data reveal features of the South Americanmonsoon Combining several network measures enhances identification of climaticpatterns Distinct large scale synchronization of extreme and most extreme rainfall events.

The Amazon region, being a large source of methane (CH4), contributes significantly to the global annual CH4 budget. For the first time, a forward and inverse modelling framework on regional scale for the purpose of assessing the CH4 budget of the Amazon region is implemented. Here, we present forward simulations of CH4 as part of the forward and inverse modelling framework based on a modified version of the Weather Research and Forecasting model with chemistry that allows for passive tracer transport of CH4, carbon monoxide, and carbon dioxide (WRF-GHG), in combination with two different process-based bottom-up models of CH4 emissions from anaerobic microbial production in wetlands and additional datasets prescribing CH4 emissions from other sources such as biomass burning, termites, or other anthropogenic emissions. We compare WRFGHG simulations on 10 km horizontal resolution to flask and continuous CH4 observations obtained during two airborne measurement campaigns within the Balanc¸o Atmosf´erico Regional de Carbono na Amazonia (BARCA) project in November 2008 and May 2009. In addition, three different wetland inundation maps, prescribing the fraction of inundated area per grid cell, are evaluated. Our results indicate that the wetland inundation maps based on remote-sensing data represent the observations best except for the northern part of the Amazon basin and the Manaus area. WRF-GHG was able to represent the observed CH4 mixing ratios best at days with less convective activity. After adjusting wetland emissions to match the averaged observed mixing ratios of flights with little convective activity, the monthly CH4 budget for the Amazon basin obtained from four different simulations ranges from 1.5 to 4.8 Tg for November 2008 and from 1.3 to 5.5 Tg for May 2009. This corresponds to an average CH4 flux of 931 mgm−2 d−1 for November 2008 and 836 mgm−2 d−1 for May 2009.

Understanding the challenge that climate change poses and crafting appropriate adaptation and mitigation mechanisms requires input from the breadth of the natural and social sciences. Anthropologys in-depth fieldwork methodology, long engagement in questions of societyenvironment interactions and broad, holistic view of society yields valuable insights into the science, impacts and policy of climate change. Yet the disciplines voice in climate change debates has remained a relatively marginal one until now. Here, we identify three key ways that anthropological research can enrich and deepen contemporary understandings of climate change.

Surface ecophysiology at five sites in tropical South America across vegetation and moisture gradients is investigated. From the moist northwest (Manaus) to the relatively dry southeast (P´e de Gigante, state of Sao Paulo) simulated seasonal cycles of latent and sensible heat, and carbon flux produced with the Simple Biosphere Model (SiB3) are confronted with observational data. In the northwest, abundant moisture is available, suggesting that the ecosystem is light-limited. In these wettest regions, Bowen ratio is consistently low, with little or no annual cycle. Carbon flux shows little or no annual cycle as well; efflux and uptake are determined by high-frequency variability in light and moisture availability. Moving downgradient in annual precipitation amount, dry season length is more clearly defined. In these regions, a dry season sink of carbon is observed and simulated. This sink is the result of the combination of increased photosynthetic production due to higher light levels, and decreased respiratory efflux due to soil drying. The differential response time of photosynthetic and respiratory processes produce observed annual cycles of net carbon flux. In drier regions, moisture and carbon fluxes are in-phase; there is carbon uptake during seasonal rains and efflux during the dry season. At the driest site, there is also a large annual cycle in latent and sensible heat flux.

Neste trabalho, objetivou-se aplicação de técnicas de sensoriamento remoto na detecção de processos de degradação de pastagens em três microbacias localizadas no município de Guararapes, SP. Para o estudo, utilizou-se uma imagem do satélite Landsat 5 TM do dia 02/02/10 e dados georreferenciados das condições das pastagens coletados entre os dias 26 e 29/01/10. Os resultados mostram variação do índice de área foliar (IAF) em função da condição da pastagem e do parâmetro L utilizado na equação do índice de vegetação SAVI. A metodologia de avaliação da cobertura vegetal da pastagem (CVP) e de obtenção de indicadores de degradação de pastagem (IDP) mostrou-se satisfatória para diferenciação de três níveis de degradação. Conforme o IDP, as pastagens das microbacias foram classificadas como levemente degradadas. No entanto, estudos futuros são necessários para obtenção de serie temporal do IDP para possível detecção de tendências positivas ou negativas no processo de degradação das pastagens.

For the first time in several years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Niña dissipated to ENSO-neutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern equatorial Pacific uncharacteristically returned to neutral conditions. Nevertheless, other large-scale climate patterns and extreme weather events impacted various regions during the year. A negative phase of the Arctic Oscillation from mid-January to early February contributed to frigid conditions in parts of northern Africa, eastern Europe, and western Asia. A lack of rain during the 2012 wet season led to the worst drought in at least the past three decades for northeastern Brazil. Central North America also experienced one of its most severe droughts on record. The Caribbean observed a very wet dry season and it was the Sahel’s wettest rainy season in 50 years. Overall, the 2012 average temperature across global land and ocean surfaces ranked among the 10 warmest years on record. The global land surface temperature alone was also among the 10 warmest on record. In the upper atmosphere, the average stratospheric temperature was record or near-record cold, depending on the dataset. After a 30-year warming trend from 1970 to 1999 for global sea surface temperatures, the period 2000-12 had little further trend. This may be linked to the prevalence of La Niña-like conditions during the 21st century. Heat content in the upper 700 m of the ocean remained near record high levels in 2012. Net increases from 2011 to 2012 were observed at 700-m to 2000-m depth and even in the abyssal ocean below. Following sharp decreases in global sea level in the first half of 2011 that were linked to the effects of La Niña, sea levels rebounded to reach records highs in 2012. The increased hydrological cycle seen in recent years continued, with more evaporation in drier locations and more precipitation in rainy areas. In a pattern that has held since 2004, salty areas of the ocean surfaces and subsurfaces were anomalously salty on average, while fresher areas were anomalously fresh. Global tropical cyclone activity during 2012 was near average, with a total of 84 storms compared with the 1981-2010 average of 89. Similar to 2010 and 2011, the North Atlantic was the only hurricane basin that experienced above-normal activity. In this basin, Sandy brought devastation to Cuba and parts of the eastern North American seaboard. All other basins experienced either near- or below-normal tropical cyclone activity. Only three tropical cyclones reached Category 5 intensity-all in the Western North Pacific basin. Of these, Super Typhoon Bopha became the only storm in the historical record to produce winds greater than 130 kt south of 7°N. It was also the costliest storm to affect the Philippines and killed more than 1000 residents. Minimum Arctic sea ice extent in September and Northern Hemisphere snow cover extent in June both reached new record lows. June snow cover extent is now declining at a faster rate (-17.6% per decade) than September sea ice extent (-13.0% per decade). Permafrost temperatures reached record high values in northernmost Alaska. A new melt extent record occurred on 11-12 July on the Greenland ice sheet; 97% of the ice sheet showed some form of melt, four times greater than the average melt for this time of year. The climate in Antarctica was relatively stable overall. The largest maximum sea ice extent since records begain in 1978 was observed in September 2012. In the stratosphere, warm air led to the second smallest ozone hole in the past two decades. Even so, the springtime ozone layer above Antarctica likely will not return to its early 1980s state until about 2060. Following a slight decline associated with the global financial crisis, global CO2 emissions from fossil fuel combustion and cement production reached a record 9.5 ± 0.5 Pg C in 2011 and a new record of 9.7 ± 0.5 Pg C is estimated for 2012. Atmospheric CO2 concentrations increased by 2.1 ppm in 2012, to 392.6 ppm. In spring 2012, for the first time, the atmospheric CO2 concentration exceeded 400 ppm at 7 of the 13 Arctic observation sites. Globally, other greenhouse gases including methane and nitrous oxide also continued to rise in concentration and the combined effect now represents a 32% increase in radiative forcing over a 1990 baseline. Concentrations of most ozone depleting substances continued to fall.