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Search Results: 1 - 5 of 5 matches for " Assireu "
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Observando o céu, quantificando as nuvens e praticando modelagem: um exercício de apoio ao aprendizado das ciências atmosféricas
Assireu, Arcilan Trevenzoli;Reboita, Michelle Sim?es;Corrêa, Marcelo de Paula;
Revista Brasileira de Ensino de Física , 2012, DOI: 10.1590/S1806-11172012000100015
Abstract: modern pedagogical concepts agree with the fact that activities that allow students to experience processes are fundamental for the perfect and complete understanding of these processes. thus, this paper presents a didactic activity which involved the combined use of observation and modeling of the process. the goal of this paper is to encourage the teachers and educators to the importance of relatively simple experiments in bring out facilitations to physics teaching
A contribution to understanding the turbidity behaviour in an Amazon floodplain
E. Alcantara, E. Novo, J. Stech, J. Lorenzzetti, C. Barbosa, A. Assireu,A. Souza
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2010,
Abstract: Observations of turbidity provide quantitative information about water quality. However, the number of available in situ measurements for water quality determination is usually limited in time and space. Here, we present an analysis of the temporal and spatial variability of the turbidity of an Amazon floodplain lake using two approaches: (1) wavelet analysis of a turbidity time series measured by an automatic monitoring system, which should be improved/simplified, and (2) turbidity samples measured in different locations and then interpolated using an ordinary Kriging algorithm. The spatial and temporal variability of turbidity are clearly related to the Amazon River flood pulses in the floodplain. When the water level in the floodplain is rising or receding, the exchange between the Amazon River and the floodplain is the major driving force in turbidity variability. At high-water levels, turbidity variability is controlled by Lake Bathymetry. When the water level is low, wind action and Lake Morphometry are the main causes of turbidity variability. The combined use of temporal and spatial data shows a good potential for better understanding of the turbidity behaviour in a complex aquatic system such as the Amazon floodplain.
On the water thermal response to the passage of cold fronts: initial results for Itumbiara reservoir (Brazil)
E. H. Alcantara,M. P. Bonnet,A. T. Assireu,J. L. Stech
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-9437-2010
Abstract: The passage of meteorological systems such as cold fronts or convergence zones over reservoirs can cause significant modifications in several aquatic variables. Cold fronts coming from higher latitudes and reaching the Southeastern Brazilian territory modify the mean wind field and have important impact over physical, chemical and biological processes that act in the hydroelectric reservoirs. The mean period of cold front passages along the Southeastern Brazilian coast is 6 days during the winter and between 11 and 14 days in the summer. Most of these fronts also affect the hinterland of S o Paulo, Minas Gerais and Goiás states. The objective of this work is to analyze the influence of cold front passages in the thermal stratification and water quality of the Itumbiara hydroelectric reservoir which is located in Minas Gerais and Goiás. The characterization of cold front passages over the study area was done through the analysis of GOES satellite images. The analyzed data set includes time series of meteorological (wind direction and intensity, short-wave radiation, air temperature, relative humidity, atmospheric pressure) and water temperature in four depths (5, 12, 20 and 40 m). The data set was acquired in the interior of the reservoir by an autonomous anchored buoy system at a sampling rate of 1 h. The stratification was assessed by non-dimensional parameter analysis. The lake number an indicator of the degree of stability and mixing in the reservoir was used in this analysis. We will show that during the cold front all atmospheric parameters respond and this response are transferred immediately to the water surface. The main effect is observed in the water column, when the heat loss in the surface allows the upwelling events caused by convective cooling due to the erosion of thermal stratification.
Inside the hydro-physics processes at the plunge point location: an analysis by satellite and in situ data
A. T. Assireu,E. Alcantara,E. M. L. M. Novo,F. Roland
Hydrology and Earth System Sciences Discussions , 2011, DOI: 10.5194/hessd-8-1193-2011
Abstract: The plunge point locates the main point of mixing between river and the epilimnion reservoir water. The plunge point monitoring is essential to understand how it will be the behavior of density currents and its implications for reservoir. The applicability of satellite imagery products from different sensors (Landsat TM band 6 thermal signatures and visible channel) for characterization of the river-reservoir transition zone is presented in this study. We demonstrate the feasibility of the Landsat TM band imagery to discern the subsurface river plumes and the plunge point. The spatial variability of the plunge point evident in the hydrologic data illustrates the advantages of synoptic satellite measurements over in situ point measurements alone to detect the river-reservoir transition zone. It is indicated that the river flowing as underflow contributes to the thermal stability of the water column during wet season (summer-autumn). During the dry season, when the river-reservoir water temperature differences vanish and the river circulation is characterized by interflow-overflow, the river water inserts into the reservoir upper layers, affecting water quality. The results indicate good agreement between hydrologic and satellite data and that the jointly use of thermal and visible channel, operational monitoring of plunge point is feasible. The deduced information about the density current from this product could potentially be assimilated for numerical modeling and hence be of significant interest for environmental and climatological research.
Hydro-physical processes at the plunge point: an analysis using satellite and in situ data
A. T. Assireu, E. Alcantara, E. M. L. M. Novo, F. Roland, F. S. Pacheco, J. L. Stech,J. A. Lorenzzetti
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: The plunge point is the main mixing point between river and epilimnetic reservoir water. Plunge point monitoring is essential for understanding the behavior of density currents and their implications for reservoir. The use of satellite imagery products from different sensors (Landsat TM band 6 thermal signatures and visible channels) for the characterization of the river-reservoir transition zone is presented in this study. It is demonstrated the feasibility of using Landsat TM band imagery to discern the subsurface river plumes and the plunge point. The spatial variability of the plunge point evident in the hydrologic data illustrates the advantages of synoptic satellite measurements over in situ point measurements alone to detect the river-reservoir transition zone. During the dry season, when the river-reservoir water temperature differences vanish and the river circulation is characterized by interflow-overflow, the river water inserts into the upper layers of the reservoir, affecting water quality. The results indicate a good agreement between hydrologic and satellite data and that the joint use of thermal and visible channel data for the operational monitoring of a plunge point is feasible. The deduced information about the density current from this study could potentially be assimilated into numerical models and hence be of significant interest for environmental and climatological research.
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