Mestrado em Engenharia Ambiental

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http://repositorio.ufes.br/handle/10/17612

Nível: Mestrado Acadêmico
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Navegando Mestrado em Engenharia Ambiental por Autor "Acuña, Joel Rojas"

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    Distribuição da temperatura da superfície do mar e dos sedimentos suspensos na plataforma continental capixaba utilizando imagens landsat5/TM
    (Universidade Federal do Espírito Santo, 2012-05-03) Teixeira, Gregório Luiz Galvão; Acuña, Joel Rojas; Aquije Chacaltana, Julio Tomás; Kampel, Milton; Mendonça, Antônio Sérgio Ferreira
    Monitoring water quality in the inner Continental Shelf (CS) has shown to be costly when conventional methods are employed. Orbital Remote Sensing appears as an alternative tool to monitoring important variables such as sea surface temperature (SST) and suspended sediment concentration (SSC). This study aims at assessing spatial distribution of SST and SSC in the continental shelf area of the Brazilian State of Espírito Santo using, respectively, Band 2 (0.569µm) and Band 6 (11.435µm) data from Thematic Mapper (TM) sensor on board of satellite Landsat 5. Thus, a data bank was built out of 127 images pre-processed and registered by the TM sensor. Of these 127 images, only 4 were selected for SST and SSC analyses. During image pre-processing, geometric and reflectance corrections are made. Geometric correction is carried out based on a second image orthorectified so that there is correct georeferencing. Reflectance correction is performed using an atmospheric compensation model. Through this model, sea surface reflectance is obtained. SST is estimated based on the adjustment of Brightness Temperature (BT) derived from Band 6 with data from the Multi-scale Ultra-high Resolution Sea Surface Temperature (MURSST). In case of not enough sediment field data to carry out curve adjustment, SSC calculation is performed using the empirical logarithm algorithm proposed by Tassan (1987), which uses Band 2 data. The corrected reflectance spectrum is compared to TOA reflectance spectrum. The corrected spectrum complied with the literature on natural targets analyzed: cloud, vegetation, water and water with sediments. Landsat BT adjustment with SST of MURSST showed to be significant, according to statistical F-test and to r 2 = 0.87. Results of the 4 scenes for SST and SSC fields. For winter SST, a more homogeneous temperature of ∼23◦C is observed, whereas the summer scene is characterized by thermal contrasts between the area closer to the coast (∼21◦C) and the area further from the coast (∼26◦C). Further, hotspot plumes associated to the mouths of Jucu and Doce Rivers and Espírito Santo Bay are also verified. For the SSC fields, higher-concentration plumes are observed, which are advected southeast. The highest concentrations are associated to the Doce River (over 60 mg/L). SSC values comply with the values reported in the relevant literature, i.e. close to the coastal line, in the summer scene, values of ∼15mg/L were verified. On the other hand, for autumn and winter scenes, these values are about ∼35mg/L. Both atmospheric correction and SSC distribution values found in this study are according to the data and studies reported in the relevant literature. Therefore, we can conclude that the method employed showed to be functional to process the data gathered in this study.
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    Método para detecção automática de vórtices
    (Universidade Federal do Espírito Santo, 2016-10-20) Freguete, Larissa Marques; Samatelo, Jorge Leonid Aching; Aquije Chacaltana, Julio Tomás; Rigo, Daniel; Carvalho, Nelson Violante; Acuña, Joel Rojas
    In the ocean, the vortices are related to western boundary currents, as the Brazil Current, that are confessedly the currents with the highest intensity. These currents have a quite vortex generation potential either being caused by barotropic or baroclinic instabilities. Hence, the goal of this work was the development of a vortex automatic detection technique by using the 3D velocity fields from de computational model HYCOM (HYbrid Coordinate Ocean Model). Without a lack of generality, the study region is the area delimited by the latitudes of 19oS - 26oS and the longitudes of 35oO - 50oO as being a site of big occurrence of vortices. The HYCOM velocity field is analyzed by layers and the localization of a existing singularity in the de velocity field is accomplished by the Poincaré Index (IP). The type of singularity is identified by using a linear dynamic model that takes in consideration the singularity’s neighborhood informations. In this work are presented three different techniques to quantify the IP. The first technique uses only the orientation field values from the velocity field, the second uses a line integral in a closed curve, and the third one uses a surface intengral. A numeric code was built and the three techniques compared by using a diagnostic assessment method. The techniques performances was evaluated considering a HYCOM velocity database where the occurring singularities was labelled manually. The measurement of the techniques performance is based on the sensibility (REC) and precision (PRE) metrics. The metrics results show the technique 3 has the best performance to identify the vortices (PRE = 73.96%, REC = 96.01%). A quasi-stationary was identified in the Cabo de São Tomé area. The vortices presented a well-developed vertical profile that reaches depths higher than 2000 m and a time length of 11 days.