Publicações

Este trabalho tem por objetivo avaliar o desempenho dos índices de vegetação NDVI (Normalized Difference Vegetation Index), EVI (Enhanced Vegetation Index) e LSWI (Land Surface Water Index) na região do Pantanal, considerando os principais tipos de cobertura da terra e os aspectos sazonais da precipitação. Para isso, foram utilizados dados do sensor MODIS, produto MOD13Q1, e estimativas mensais de precipitação do satélite TRMM, produto 3B43. As análises foram feitas por meio de transectos ao longo das regiões, utilizando como referência o mapa de cobertura da terra compatibilizado com as classes de vegetação e usos considerada no modelo de superfície SSiB (Simplified Simple Biosphere Model). Os resultados mostraram que, na estação seca, o NDVI tende a apresentar os maiores valores, entre 0,4 e 0,8; enquanto o LSWI ficou entre 0,0 e 0,4, exceto para a classe Floresta Perene. O EVI apresentou valores intermediários, entre 0,2 e 0,6. Todos os índices mostraram baixa correlação com a precipitação na estação seca, inferiores a 0,25. Na estação chuvosa, o NDVI registrou os maiores valores em quase toda a extensão dos transectos, variando entre 0,6 e 0,8. Apenas em alguns setores da classe Floresta Perene, os valores de LSWI foram superiores ao NDVI. O EVI, em geral, mostrou os valores mais baixos entre os índices, entre 0,2 a 0,5. O LSWI apresentou valores intermediários entre o NDVI e o EVI, de 0,2 a 0,7. Nas classes Cerrado e Chaco, os índices LSWI e EVI ficaram bastante próximos, alternando-se por vezes. O NDVI e o LSWI mostram correlações significativas com a precipitação (α = 5%) em todas as classes de cobertura. Em relação à amplitude (diferença entre máximos e mínimos), o LSWI apresentou a maior variação em todas as classes e, em ambas as estações. O LSWI mostrou-se mais adequado para estudos na região do Pantanal, por captar melhor as variações da vegetação, especialmente no Cerrado e Caatinga na estação chuvosa; e Floresta Perene na estação seca.

This paper presents the evaluation of gaussian models of air quality AERMOD and ISC, highly used for regulatory purposes. The study area was Nova Iguaçu city and the period considered was the summer of 2002. For the simulations we considered the emission of SO2 pollutant from 24 stationary sources and 22 mobile sources in the simulations represented by area and line sources respectively. The model results were compared, in order to examine the best performance for their applications. The analysis was performed with statistical indices recommended in the literature for evaluating air quality models.

Deforestation of tropical forests for logging and agriculture, associated to slash-and-burn practices, is a main contributor of CO2 emissions, both immediate due to biomass burning and future due to the elimination of a potential CO2 sink. Moreover, climate change in the Amazon during the 21st century is projected to decrease the resilience of the Amazon forest and possibly replace large parts of tropical forests with savannas, adding to the direct anthropogenic deforestation. The potential feedbacks between LUCC (Land-Use and Land-Cover Change) and climate change are thought to further increase the loss of tropical forests and increase the rate of CO2 emissions, through mechanisms such as land and soil degradation and the increase in wildfire occurrence and severity. However, current understanding of the processes of fires (including ignition, spread and consequences) in tropical forests and feedbacks with climate are poorly understood and need further research. As the processes of LUCC and associated fires occur at local scales, linking them to large-scale atmospheric processes requires a means of up-scaling higher resolutions processes to lower resolutions. Our approach is to couple models which operate at various spatial and temporal scales: a Global Climate Model (GCM) (and possibly a Regional Climate Model; RCM), Dynamic Global Vegetation Model (DGVM) and local-scale LUCC model and fire behavior model. The climate model(s) resolve larger scale atmospheric processes and forcings, which are felt by the surface DGVM and fed-back to the climate. Higher-resolution processes such as deforestation, land use management and associated (as well as natural) fires are resolved at the local level. Anthropogenic LUCC (such as deforestation and pasture burning) is modeled using Geographical Information Systems (GIS) and spatially-explicit models. Modifications to the land surface are imposed on the land model, which has a potential feedback on the land surface properties through processes resolved by the atmospheric and land models. Fire behavior is modeled at the regional scale (~100m) to represent the detailed landscape using semi-empirical or empirical fire spread models. Improved parametrizations from our fully-coupled experiments, for use in atmospheric and land surface models, will allow for a better understanding and evaluation of CO2 emissions from LUCC and feed-backs with climate change.

Severe hydrological droughts in the Amazon have generally been associated to strong El Niño events. More than 100 years of stage record at the port of Manaus confirm that minimum water levels generally coincide with intense warming in the tropical Pacific sea waters. During 2005, however, the Amazon experienced a severe drought with great ecological and social impact, and who was not associated to an El Niño event. Unless what usually occur during strong El Niño events, when negative rainfall anomalies usually affect central and eastern Amazon drainage basin; rainfall deficiencies in the drought of 2005 were spatially constrained to the west and southwest of the basin. In spite of this, discharge stations at the main stem recorded minimum water levels as low as those observed during the basin-wide 1996-97 El Niño related drought. Besides this, stage data and satellite images indicate that floodplain lakes surface areas were more reduced during the recent drought. This paper examines why river discharges were so low during the 2005, even though rainfall deficits were restricted to a fraction of the whole basin, and why the impacts on the main stem floodplain were so severe. The analysis of river discharges along the main stem and major tributaries during the drought of 2005 revealed that the recession on major tributaries began almost simultaneously. This was not the case in the 1996-97 drought, when above normal contribution of some tributaries for a short period during high water were crucial to partially counter balance high discharge deficits of the other tributaries. Since time-lagged contributions of major tributaries are fundamental to damp the extremes in the main stem, an almost coincident recession in almost all tributaries caused a rapid decreased of water discharges during the 2005 event. Perhaps one of the most important lessons to be learnt from the drought of 2005 is that, from a hydrological point of view, more importantly than the size of the area affected by negative rainfall anomalies is the timing and location where those rainfall deficits occur. In conclusion, localized drought might have a greater impact on main stem river discharges providing rainfall deficiencies produces a simultaneous recession of major tributaries.

We evaluated the soybean cycle duration (in days) for an agricultural region in the state of Parana, Brazil, under A1B climate change scenario. The scenario was generated by the Eta model nested into the conditions of HadCM3 model (Eta / CPTEC). We selected four locations (Cândido de Abreu, Cerro Azul, Ponta Grossa and Telemaco Borba) and we considered two periods: present climate (1961-1990) and future climate (2011-2100). The model presented good performance for the soybean cycle duration during the current climate. It was observed for all locations, a soybean cycle reduction on projections for future scenarios due to the increase in air temperature. In the future scenario, from 2071 to 2100, Ponta Grossa and Telemaco Borba locations showed a reduction of 55 and 45 days, respectively.

Simulations for the present climate (1961-1990) in the resolution of 40 km were produced on the South America with the regional model Eta forced by HADCM3 as lateral boundary conditions. The Eta Model was adapted to carry through integrations of decadal timescale for studies of climate change scenarios. This work has as objective to adjusting the simulations of the present climate for São Paulo state, using statistical correction over model grid-boxes, according to daily precipitation of 20 meteorological stations. Simulations of the present climate show that the largest precipitation amounts to the east of the State with annual average values varying between 5 and 7 mm/day. In central part of the State the daily means are below 4 mm/day. The rainy (drier) season occurs between the December and February (June and August) months with values above (below) 11 mm/day (1 mm/day) in the stations located near the coast (middle) of the State. In general, the rainy months (drier) exhibited negative (positive) bias, therefore underestimated (overestimated) the precipitation. The adjustment method consisted of determining a correction factor according to monthly precipitation bias in the period between 1961 and 1985, the corrections were applied in the period between 1986 and 1990 (test period). The method was evaluated based on the mean absolute error (MAE), the root mean square error (RMSE) and the Skill Score before and after corrections. The performance of the method has been classified subjectively such as: Excellent, when the method reduced model errors (bias, MAE e RMSE) in most of the months, Satisfactory and Unsatisfactory, when errors increased after correction. In general, it was noticed that the method satisfactorily adjusted the simulations in most of the State, mainly in the stations where largest bias occurred near the coast. In the stations where the method did not perform satisfactorily the values of the simulated precipitation were generally similar to the observations, the stations with unsatisfactory behavior were located in central north of São Paulo state. These corrections will be applied to simulations of future climate change scenarios to support vulnerability studies.

O conhecimento dos impactos das mudanças nos usos da terra sobre o tempo e clima, tanto no presente quanto no futuro, têm apresentando grande interesse nas pesquisas realizadas atualmente. Muitos estudos mostram que o decorrente desmatamento da região amazônica irá influenciar diretamente o clima futuro, modificando de forma significativa o comportamento da temperatura e precipitação sobre a América do Sul. Neste contexto, a utilização de mapas que representem de forma mais realística os usos da terra torna-se necessária. Sendo assim, o presente trabalho avaliou quais os possíveis impactos na modelagem atmosférica da utilização de um mapa mais atual de vegetação e usos da terra do Brasil. Os resultados obtidos mostraram mudanças praticamente insignificantes nas simulações para o mês de junho de 2008. Notou-se que uma melhor representação dos processos atmosféricos relacionados com a presença de áreas urbanas levaria a simulações mais realísticas. No contexto geral, modificações do balanço de energia em superfície causadas por condições da superfície seriam mais bem observadas em simulações de curto prazo. Mesmo assim, torna-se necessário que mapas representativos das atuais condições de vegetação e usos da terra sejam utilizados na modelagem atmosférica objetivando uma melhoria nos resultados esperados.

The Amazon, with an area of about 6.5 million km2 is the largest Brazilian biome and home of the largest remaining tropical forest. The Amazon basin includes the largest world river system, encompassing ten large sub basins, undergoing various degrees of anthropic changes. Among major basins, the Tapajoss River, with a drainage area of 492,481 km2, is being affected by severe land use and land cover changes because of the high rates of deforestations at rivers headwaters. The Tapajos basin is of the great importance from an economic point of view, because governmental development plans for the basin includes the construction of seven large hydroelectric projects, and the paving of the BR-163 road, which connects important regions of soybean production and large population centers. All those actions have the potential to affect the whole basin hydrological response. Moreover, the regions vulnerability on climate change, could impact the hydrological cycle at different time scales, including sediments load, in stream biogeochemical cycling, and the frequency of droughts and floods. In this context, it is necessary to understand how the change of land use and climate change affect the hydrology of the catchment. In this study, the large basin hydrological model – MGB, using ETA atmospheric model as an input for present climate (1970-1990), was compared to observed discharges.

In this study was realized an analysis and comparison of the precipitation field predicted by climatic regional model ETA of CPTEC and the precipitation field of the database PROCLIMA/CPTEC correspondent the observed data. The existence for possible systematic errors was checked. The study was realized on the northeast of Brazil for the period 1970-1990. Systematic errors associated with precipitation fields of the ETA model were found and these were corrected through the curve of probability occurrence of the precipitation data observed, obtaining satisfactory values after correction.

A simulação do comportamento hidrológico de bacias hidrográficas consiste em uma das principais ferramentas na gestão dos recursos hídricos, devido à possibilidade de predição dos impactos hidrológicos das mudanças do uso da terra e do cambio climático. Neste sentido, o presente trabalho objetivou a aplicação de um modelo hidrológico de macro-escala na bacia do Rio Madeira com intuito em estudar os processos hidrológicos da região. Para a simulação do ciclo hidrológico na região, foram coletadas informações por meio de sensoriamento remoto, tais como: mapas de solo, vegetação e uso da terra; e o modelo digital de elevação do terreno. Também foram coletados dados de chuva e meteorológicos da base de dados existente no Grupo PROCLIMA do CPTEC/INPE. A classificação de solos e valores de parâmetros associados foram obtidos da EMBRAPA/IBGE e da fundação ISRIC – World Soil Information, também conhecida como SOTERLAC. Após a coleta, os dados foram preparados para alimentação de um modelo de grandes bacias. Devido às anomalias e ausência de dados fluviométricos, necessitou-se de uma criteriosa análise e busca de fontes alternativas que fornecessem informações consistentes para o período escolhido para o estudo (entre 1970 à 1990). Nesta etapa de pré-processamento dos dados, foram utilizadas diferentes metodologias de processamento à atingir resultados aceitáveis , onde, obtiveram-se os objetos hidrológicos constituídos no processo de representação do ciclo, utilizando ferramentas de geoprocessamento e programas computacionais em FORTRAN essenciais à execução da tarefa. Cito como resultados desta etapa: modelo digital de elevação corrigido (depressões preenchidas), direções de fluxo, área acumulada, rede de drenagem, delimitação de sub-bacias, trechos de rio, declividades, classificação dos tipos de solos e vegetação, e dados das estações meteorológicas selecionadas. Para a calibração do modelo hidrológico foram definidos os valores dos parâmetros de solos, de vegetação e parâmetros fixos, focando a geração de vazões semelhantes às observadas. Os valores dos parâmetros de vegetação e solo para a simulação foram obtidos a partir de diversos trabalhos presentes na literatura existente atual; Já os parâmetros fixos foram definidos a partir das informações gerais do modelo, como por exemplo, início da simulação, número de células, etc. Para dar continuidade a este trabalho de iniciação cientifica e avaliação da acurácia do modelo hidrológico de grandes bacias em representar o comportamento hidrológico na bacia do Madeira, ficam determinadas a seguintes atividades: execução das tarefas de calibração, simulação e previsão para o modelo.

The biomass burning, which occur mostly in tropical areas of the planet, are important sources of particulate matter to the atmosphere. In South America, during the Austral winter, thousands of vegetation fires occur in the forest ecosystems. These fires occur primarily in the Amazon and Central Brazil regions, however, through atmospheric transport of this emissions, they can produce a spatial distribution of smoke over an extensive area of about 4-5 millions km2, much higher than the area where they fires took place. During the combustion process, aerosol particles are emitted into the atmosphere and they can interact efficiently with solar radiation and affect the dynamic and microphysical processes of cloud formation and air quality. Land cover use changes can affect the energy balance due modification of surface albedo and evapotranspiration capacity, which can influence the fluxes of latent heat and sensible heat emitted by surface and the hydrological cycle. In this study, we estimate emissions of biomass burning aerosols using projected scenarios of land use (correspondent to the years 2007 to 2030) and investigate the effects of land cover use change on the surface fluxes, which also affect the hydrological cycle and near surface thermodynamics properties over South America, especially in the Amazon region. This study was performed numerically with the regional circulation model CCATT-BRAMS. In this modeling system the radiation parameterization takes into account the interaction between biomass burning aerosols and short and long wave radiation. The impact of biomass burning aerosols is also computed through an auto-conversion formulation based on the cloud condensation nuclei (CCN) availability at cloud base in the convective parameterization. The surface scheme (LEAF-3) was tuned using field campaign observational data, in particular, the water extraction by vegetation using a new parameterization of root profiles. Model results showed a reduction of precipitation in the projected scenarios and a net increase of near-surface temperature. These changes are associated with an augment of sensible heat due land/cover use change as well as the effect of aerosol on the hydrological cycle.