Publicações

Two simultaneous extreme events affected tropical South America to the east of the Andes during the austral summer and fall of 2012: a severe drought in Northeast Brazil and intense rainfall and floods in Amazonia, both considered records for the last 50 years. Changes in atmospheric circulation and rainfall were consistent with the notion of an active role of colder-than-normal surface waters in the equatorial Pacific, with above-normal upward motion and rainfall in western Amazonia and increased subsidence over Northeast Brazil. Atmospheric circulation and soil moisture anomalies in the region contributed to an intensified transport of Atlantic moisture into the western part of Amazonia then turning southward to the southern Amazonia region, where the Chaco low was intensified. This was favored by the intensification of subtropical high pressure over the region, associated with an anomalously intense and northward-displaced Atlantic high over a relatively colder subtropical South Atlantic Ocean. This pattern observed in 2012 was not found during other wet years in Amazonia such as 1989, 1999, and 2009. This suggests La Nina as the main cause of the abundant rainfall in western Amazonia from October to December, with wet conditions starting earlier and remaining until March 2012, mostly in northwestern Amazonia. The anomalously high river levels during the following May-July were a consequence of this early and abundant rainy season during the previous summer. In Northeast Brazil, dry conditions started to appear in December 2011 in the northern sector and then extended to the entire region by the peak of the rainy season of February-May 2012.

The National Program for Production and Use of Biodiesel (PNPB), launched in Brazil, is based on the diversification of its feedstock and social inclusion. Among the various oilseeds, palm was identified as the ideal one for the Northern region. However, the participation of palm is still not representative in the Brazilian biodiesel matrix. The key industrial challenges to promote oil palm in the biodiesel sector (as well as surpass them) are represented in the data presented herein. The current level of production is not enough to meet the industry’s needs. The use of this oil appears to be a viable possibility in the medium-term. However technological limitations, infrastructure, transaction costs and high investments are pivotal bottlenecks to promote palm in the biodiesel chain. Concerning social promotion, there are not enough results yet. The prolonged process of economic marginalization, which family farmers have undergone in the Northern region, results in companies having to engage in social activities that aim at deeper cultural changes.

The response of the global climate system to atmospheric CO2 concentration increase in time is scrutinized employing the Brazilian Climate Model (BESM-OA2.3). Through the achievement of over two thousand years of coupled model integrations in ensemble mode, it is shown that the model simulates the signal of recent changes of global climate trends, depicting a steady atmospheric and oceanic temperature increase and corresponding marine ice retreat. The model simulations encompass the time period from 1960 to 2105, following the Coupled Model Intercomparison Project 5 (CMIP5) protocol. Notwithstanding the accurate reproduction of large scale ocean-atmosphere coupled phenomena, like the ENSO phenomena over the Equatorial Pacific and the interhemispheric gradient mode over the Tropical Atlantic, the BESM-OA2.3 coupled model shows systematic errors on sea surface temperature and precipitation which resemble those of other global coupled climate models. Yet, the simulations demonstrate the models potential to contribute to the international efforts on global climate change research, sparking interest in global climate change research within the Brazilian climate modeling community, constituting a building block of the Brazilian Framework for Global Climate Change Research.

Extreme weather continues to preoccupy society as a formidable public safety concern bearing huge economic costs. While attention has focused on global climate change and how it could intensify key elements of the water cycle such as precipitation and river discharge, it is the conjunction of geophysical and socioeconomic forces that shapes human sensitivity and risks to weather extremes. We demonstrate here the use of high-resolution geophysical and population datasets together with documentary reports of rainfall-induced damage across South America over a multi-decadal, retrospective time domain (1960-2000). We define and map extreme precipitation hazard, exposure, affected populations, vulnerability and risk, and use these variables to analyse the impact of floods as a water security issue. Geospatial experiments uncover major sources of risk from natural climate variability and population growth, with change in climate extremes bearing a minor role. While rural populations display greatest relative sensitivity to extreme rainfall, urban settings show the highest rates of increasing risk. In the coming decades, rapid urbanization will make South American cities the focal point of future climate threats but also an opportunity for reducing vulnerability, protecting lives and sustaining economic development through both traditional and ecosystem-based disaster risk management systems.

This study analyzes the inter-annual variability (IAV) of simulations of 21 different land surface model formulations, driven by meteorological conditions measured at 8 flux towers, located in rain forest, forest-savanna ecotone and pasture sites in Amazonia, and one in savanna site in Southeastern Brazil. Annual totals of net ecosystem exchange (NEE) of carbon and evapotranspiration (ET), measured and simulated by each model for each site-year, were compared in terms of year-to-year variability and possible relation to climate drivers. Results have shown that most of models simulations for annual totals of NEE and ET, and IAV of these fluxes, are frequently different from measurements. The average of the model simulations of annual fluxes tend to respond to climatic drivers similarly to the observations, but with noticeable discrepancies. Annual measurements of NEE are negatively correlated to annual rainfall in the forest sites group. Although the ensemble of all models yields a similar result, only three model formulations reproduce a significant negative correlation of simulated NEE with rainfall. For the IAV of ET, tower measurements are controlled by annual variations of radiation and this feature is captured by the ensemble of the models, both at individual sites and when all forest sites are grouped. However, simulated ET values are also significantly correlated to the amount of precipitation in many models and in the model ensemble, while there is no significant correlation in the observations. In general, the surface models are able to reproduce the responses of fluxes to climatic drivers, but improvements are still needed to better capture their inter-annual variability.

Wild-fires release huge amounts of aerosol and hazardous trace gases in the atmosphere. The residence time and the dispersion of fire pollutants in the atmosphere can range from hours to days and from local to continental scales. These various scenario shighly depend on the injection height of smoke plumes. The altitude at which fire products are injected in the atmosphere is controlled by fire characteristics and meteorological conditions. Injection height however is still poorly accounted in chemistry transport models for which fires are sub-grid scale processes which need to be parametrised. Only recently, physically-based approaches for estimating the fire injection heights have been developed which consider both the convective updrafts induced by the release of fire sensible heat and the impact of background meteorological environment on the fire convection dynamics. In this work, two different models are used to simulate fire injection heights in contrasted meteorological scenarios: a Mediterranean arson fire and two Amazonian deforestation fires. A Eddy-Diffusivity/Mass-Flux approach, for merly developed to reproduce convective boundary layer in the non-hydrostatic meteorological model Meso-NH, is compared to the 1-D Plume Rise Model. For both models, radiosonde data and re-analyses from the European Center for Medium-Range Weather Forecasts (ECMWF) have been used as initial conditions to explore the sensitivity of the models responses to different meteorological forcings. The two models predict injection heights for the Mediterranean fire between 1.7 and 3.3 km with the Meso-NH/EDMF model systematically higher than the 1-D PRM model. Both models show a limited sensitivity to the meteorological forcings with a 2030 % difference in the injection height between radiosondes and ECMWF data for this case. Injection heights calculated for the two Amazonian fires ranges from 5 to 6.5 km for the 1-D PRM model and from 2 to 4 km for the Meso-NH/EDMF model. The difference of smoke plume heights between the two models can reach 34 km. A large difference is obtained for the windy-wet Amazonian fire by the 1-D PRM model with a injection height 1.5 km higher when ECMWF re-analyses are used compared to the run with the radiosonde forcing. For the Mediterranean case, both models forecast a plume injection height above the boundary layer, although there are evidences that this particular fire propagated near the surface, highlighting the current limitations of the two approaches.

Cloud cover is a key feature in Earth images acquired from space. Cloud cover data play a significant role in the weather forecast and climate knowledge, as well as in several human activities. Several studies have been conducted to establish a methodology and experimental setup in order to acquire reliable cloud cover data from remote sense observations performed on the surface. This research aimed at comparing ground data acquired by different systems for the same atmospheric scenario regarding cloud cover. Solar radiation data and sky images acquired at SONDA station located in Florianópolis, in 2002, were used to evaluate cloud cover. Also, cloud cover data collected at the international airport meteorological station distant 7,700 m from the SONDA station were used. This work compares these two sets of data acquired for sky scenarios with only one type of cloud. The results show good agreement in clear and completely overcast sky conditions. Future studies using longer time series will be developed in order to evaluate the influence of seasonal variability and atmospheric scenarios with several cloud types (low, medium and high clouds).

O primeiro passo para o gerenciamento participativo das Bacias hidrográficas é identificar os diferentesprotagonistas sociais que atuam na gestão dos recursos hídricos. Para que em seguida, os atores sociais, atravésdo processo de educação ambiental, na capacitação de gestores públicos, técnicos, agentes de desenvolvimentolocal, educadores, professores e lideranças em geral, saibam avaliar as demandas dos demais usuários e tomemdecisões conscientes no âmbito do Comitê de Bacia hidrográfica. A escolha da Bacia hidrográfica do Rio Munin,foi devido aos problemas ambientais e o baixo grau de instrução sobre educação ambiental na região. Assim essetrabalho teve como objetivo sistematizar os dados secundários sobre os aspectos políticos, ambientais e sociaisem toda área de abrangência da Bacia, demonstrando os passos para iniciar o processo de capilaridade efortalecimento da educação ambiental, voltados para a instrumentalização e fortalecimento do Comitê dessaBacia hidrográfica. Este trabalho baseou-se no Projeto União Pró-Águas do Alto e Médio Munin, seguindo asinformações obtidas da Rede de Monitoramento da Qualidade e Quantidade da Água, implantada peloPNMAII/MMA. Foram identificadas na Bacia do Munin 114 organizações da sociedade civil, 101 usuários, 28instituições ligadas ao governo municipal, 21 ao estadual e 2 federais que participam da implantação desseComitê. De acordo com a percepção dos moradores, uma das ações mais perturbadoras detectadas na Bacia é adevastação da mata ciliar por desmatamentos e queimadas, que causa o assoreamento do rio. O que se pôdeconstatar é que o grau de desinformação sobre a gestão das águas nos da a certeza que a implantação de umarede de educação ambiental contribuirá de forma eficaz não só na implantação do Comitê da Bacia, como paraimplantação de políticas públicas no desenvolvimento regional.

Bipolar lightning is usually defined as a lightning flash where the current waveform exhibits a polarity reversal. There are very few reported cases of cloud-to-ground (CG) bipolar flashes using only one channel in the literature. Reports on this type of bipolar flashes are not common due to the fact that in order to confirm that currents of both polarities follow the same channel to the ground, one necessarily needs video records. This study presents five clear observations of single-channel bipolar CG flashes. High-speed video and electric field measurement observations are used and analyzed. Based on the video images obtained and based on previous observations of positive CG flashes with high-speed cameras, we suggest that positive leader branches which do not participate in the initial return stroke of a positive cloud-to-ground flash later generate recoil leaders whose negative ends, upon reaching the branch point, traverse the return stroke channel path to the ground resulting in a subsequent return stroke of opposite polarity. Key Points Existence of single-channel bipolar flashes Common characteristics of bipolar flashes How can positive and negative discharges use the same path to ground?

We investigated the seasonal patterns of Amazonian forest photosynthetic activity, and the effects thereon of variations in climate and land-use, by integrating data from a network of ground-based eddy flux towers in Brazil established as part of the ‘Large-Scale Biosphere Atmosphere Experiment in Amazonia’ project. We found that degree of water limitation, as indicated by the seasonality of the ratio of sensible to latent heat flux (Bowen ratio) predicts seasonal patterns of photosynthesis. In equatorial Amazonian forests (5° N-5° S), water limitation is absent, and photosynthetic fluxes (or gross ecosystem productivity, GEP) exhibit high or increasing levels of photosynthetic activity as the dry season progresses, likely a consequence of allocation to growth of new leaves. In contrast, forests along the southern flank of the Amazon, pastures converted from forest, and mixed forest-grass savanna, exhibit dry-season declines in GEP, consistent with increasing degrees of water limitation. Although previous work showed tropical ecosystem evapotranspiration (ET) is driven by incoming radiation, GEP observations reported here surprisingly show no or negative relationships with photosynthetically active radiation (PAR). Instead, GEP fluxes largely followed the phenology of canopy photosynthetic capacity (Pc), with only deviations from this primary pattern driven by variations in PAR. Estimates of leaf flush at three non-water limited equatorial forest sites peak in the dry season, in correlation with high dry season light levels. The higher photosynthetic capacity that follows persists into the wet season, driving high GEP that is out of phase with sunlight, explaining the negative observed relationship with sunlight. Overall, these patterns suggest that at sites where water is not limiting, light interacts with adaptive mechanisms to determine photosynthetic capacity indirectly through leaf flush and litterfall seasonality. These mechanisms are poorly represented in ecosystem models, and represent an important challenge to efforts to predict tropical forest responses to climatic variations.