Publicações

Este trabalho apresenta um estudo comparativo, no qual se avalia a eficácia e a eficiência de três ferramentas computacionais para a delimitação de bacias hidrográficas e a extração da rede de drenagem, a partir de dados altimétricos oriundos de diferentes fontes: imagens SRTM originais da USGS (90 metros), imagens SRTM interpoladas (30 metros) do projeto TOPODATA e imagens ASTER (30 metros). As ferramentas computacionais utilizadas foram o módulo ArcHydro da solução comercial ArcGIS, o software livre TerraHidro e o módulo livre HAND executável em IDL. Foram avaliadas as dificuldades e facilidades no uso dos dados, o tempo de processamento e os produtos obtidos para o caso da bacia do rio Doce. Tanto os dados de entrada, quanto as ferramentas utilizadas, apresentaram diferenças quanto ao tempo de processamento e à facilidade de uso dos dados, fatos que devem ser considerados antes de um estudo, especialmente em bacias de médio e grande porte.

This paper presents ongoing research results of an extensible visualization pipeline for real-time exploratory analysis of spatially explicit simulations. We identify the 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. Experiments for performance analysis have shown that combining multithreading and the BlackBoard design pattern reduces the visualization response time in 50%, with no significant increase in memory consumption. The components presented in this paper have been integrated in the TerraME modeling platform for simulation of terrestrial systems.

Hydrological response results from innumerous processes interacting at different spatial and temporal scales and with various intensities. Since the hydrological impacts of Land use and land cover change (LUCC) and climate variability (CV) are strongly dependent on soil water flow pathways, an adequate representation of the runoff generation mechanisms are crucial to assess the hydrological impacts of LUCC and CV on a basin scale. Model responses to LUCC depend on structure and parameterizations used in the model. There are two basic methodologies adopted to define the structure of the hydrological model: downward and upward approaches. Upward approach is more appropriate for identifying causal relationships, but their results are highly affected by assumptions used in the development of the model. Besides, model structure and parameters values definition are strongly affected by scale issues and their inter-relationships. Downward approach is more appropriate for studying the effects of LUCC, but casual relationships are more difficult to identify. MGB-INPE model was developed based on the Large Scale Basins Model of Brazilian Institute of Hydraulic Research (MGB-IPH). It uses the Xinanjiang Model approach for soil water capacity distribution at each cell combined with TopModel philosophy. Both methodologies follow a downward approach: the hydrologic response of the basin is associated with patterns of self-organization observed at the basin-scale. The model was applied in the Ji-Parana Basin (JPB), a 30.000-km2 basin in the SW Amazonia. The JPB is part of the Deforestation Arc of Amazonia in Brazil and it has lost more than 50 % of his forest cover since the 80s. Simulations were performed between 1982 and 2005 considering annual land use and land cover change. MGB-INPE model was able to represent the impact of LUCC in the runoff generation process and its dependence with basin topography. Simulation results agree with observational studies: LUCC impacts in fast response processes are marked in sub-basins with steep slopes; while in basins with more gently topography the impacts are more pronounced in slow responses processes. The model was not able to capture the dependence of LUCC impacts on spatial scales: results from simulations have shown the impact increases almost linearly with basin scale, while analysis based on observed data have indicated that impacts are diluted at larger scales. These discrepancies are probably associated with limitations in the spatial representation of heterogeneities within the model, which become more relevant at larger scales. For instance, land use sub-grid variability is accounted only through the percentage of each land use within the cell, without an explicit representation of the location of each use within the gridcell, nor the interaction between land uses.

A virtual globe to visualize time series of pixels from the MODIS sensor over the South American continent is available in the Internet and was developed at the Brazilian Institute for Space Research. The MODIS images acquired since the year 2000 were transformed to a vegetation index (EVI2, two-band Enhanced Vegetation Index) with pixel size of 250 m. This study aims to use these time series to identify land use changes (LUC) based on the temporal profile of EVI2 values of deforested polygons between 2007 and 2011 within the context of the Soy Moratorium. Deforested polygons were divided in two strata: with and without soy in crop year 2010/11. From the MODIS/EVI2 time series the following classes were identified: forest, degraded forest, total clearing of the area, regrowth of forest, regrowth with pasture, pasture, agriculture, and soy. For stratum 1, the dominant LUC trajectory was: forest degradation regrowth / regrowth with pasture. In the second stratum we observed two main LUC trajectories: 1) forest degraded forest total clearing of the area annual crop (rice) soy; and 2) forest total clearing of the area annual crop (rice) soy. For most samples of stratum 2 the LUC trajectory was agriculture (e.g., rice) between total clearing and soy cultivation. These patterns occurred on average over two harvests, which may be considered the necessary time for soil correction and total removal of above ground stumps and roots to enable mechanized soy harvesting. The fast evaluation of one hundred polygons during 11 years was only possible due to the virtual globe to visualize the MODIS time series that proved to be an important tool to improve the understanding of LUC dynamics in the Amazon region.

A definição de um local para um futuro parque eólico é um processo longo em que são necessárias séries de dados meteorológicos com medidas locais a fim de avaliar com maior precisão a densidade de potência eólica da região. No entanto, a escassez de dados meteorológicos de superfície ou de ar superior no Brasil e os custos para a implantação e operação de um sistema de aquisição de dados por um período suficientemente longo tem sido considerado uma barreira para o crescimento do setor. Como alternativa para suprir esta carência de dados, a modelagem atmosférica vem sendo empregada. Porém esta metodologia está limitada em função dos recursos computacionais que restrigem a resolução temporal e espacial dos dados gerados. Dessa forma, as variáveis meteorológicas são representativas para uma determinada área (pontos de grade), os processos físicos podem ser mal simulados em razão da adequação das parametrizações adotadas para executação do modelo. O modelo atmosférico BRAMS (Brazilian Regional Atmospheric Modeling System) incorpora adequações na modelagem física com o intuito de representar da forma mais acurada os processos físicos da região tropical em que o Brasil está localizado. Este trabalho mostra os resultados de um estudo comparativo entre a velocidade do vento medida em duas torres anemométricas situadas nas regiões costeira e agreste do estado de Alagoas (Nordeste do Brasil) com as simulações obtidas a partir do modelo BRAMS executado com duas resoluções horizontais diferentes (8x8km e 2x2km) para os meses de maio (período de chuvas) e novembro (estação seca) de 2008 e adotando diferentes parametrizações de camada limite, convecção, microfísica de nuvens e radiação.

This paper reviews the information available on the dependence of negative cloud-to-ground (CG) lightning characteristics on geographical location. From the information available in the literature at the present time, there is no conclusive evidence of a significant dependence of negative CG lightning parameters on geographical location, except maybe for current intensity (first and subsequent stroke peak current and average continuing current), for which a small (less than 50% variation) dependence may exists, and multiplicity. Nevertheless, it cannot rule out that the differences in current measurements are due to reasons other than geographical location.