Argemiro Lucena Araújo

DESEMPENHO DE METODOLOGIAS PARA ESTIMATIVA DO SALDO DE RADIAÇÃO A PARTIR DE IMAGENS MODIS

The present study intends to evaluate the performance of different methodologies used in estimating the instantaneous net radiation (Rn), which is the main energy source to various natural processes occurring on the surface of our planet. The study area belongs to the Mogi Guacu River Basin. The surface data used for the Rn calibration and validation are from two micrometeorological towers located in areas of cerrado and sugarcane. MODIS sensor images and the SEBAL, METRIC and Bisht et al. methodologies were compared. Rn in the cerrado area always showed higher values than that of sugarcane, indicating that, in those wild areas, there is therefore a greater amount of energy to transform into latent and sensible heat fluxes. The employed methodologies were quite satisfactory, with a best performance of the METRIC methodology. The fact that the methodology Bisht et al. does not require surface data appears to be quite useful, since in the absence of surface measurements it has been a frequent and no-cost option for the user to make estimates of net radiation.

Obtenção do saldo de radiação em áreas de pastagem e floresta na amazônia (estação seca) através do sensor MODIS

The main objective of this study was to analyze comparatively the estimate of net radiation at surface (Rn) from orbital images with surface measured data as well as the components of Rn, for two different types of vegetation (pasture and forest) under tropical-humid climate. This study was conducted at Rondonia State in northwestern Brazil. To carry out the analysis using remote sensing techniques seven orbital images of MODIS sensor aboard the Aqua satellite were used for the algorithm implementation, and the measured surface data at two micrometeorological towers installed in the pasture and forest locations. The main results obtained from MODIS images show consistent maximum and minimum percentage error (PE) for Rn , 3% and 0.02% for the forest area and 10% and 0.7% for the pasture area. These results show that remote sensing is an important and effective tool in environmental and hydrological studies.

Refinamento de imagens termais do Landsat 5 - TM com base em classes de NDVI

The objective of this study was to use a simplified method based on NDVI classes for the sharpening of the Landsat 5 - TM surface temperature images (Ts) obtained during the years of 2005 and 2006. Thus, three sharpening models, based on the linear regression method, were proposed and compared. The relative and the root mean square errors obtained through the suggested models were of 0.37% and 1.38 oC, respectively, while the original model presented root mean square error of 1.32 oC. It was verified that the errors obtained with the accomplished calibrations did not significantly influence in the average values of the thermal images and the results contributed substantially to the improvement of their spatial resolution. The sharpening allowed the precise identification of the targets and features undetectable at the original spatial resolution. This evidences that the simplified method, suggested in this study, allows an accurate sharpening more easily applicable than the original model.

Modelagem Simplificada Para Estimativa do Balanço de Energia à Superfície em Escala Regional (R-SSEB)

Abstract This study presents a simplified methodology and adjusted from existing algorithms of orbital sensor data available fortheNortheastregionofBrazil(NEB)inordertooperationalizethespatialdeterminationofevapotranspiration(ET)onlywith remote sensing data, using Terra/MODIS data from 2002 to 2011. The results for various targets around the NEBwere compared with CLM ( Common Land Model) and MOD16 data. Was obtained average percentage error (MPE) andmean absolute error (MAE) of 23,6% and 181 mm.year -1 , respectively, when compared to CLM data. It was evaluatedthe ET obtained by the proposed algorithm with MOD16 ET data, resulting in EMP and EMA of 38,6% and 288mm.year -1 , respectively. The average annual data from ET ranged 482-1105 mm.year relating to areas of Caatinga andtropical rainforest, respectively. The results presented are consistent with the literature and showed that the proposedmethodology enables operationalize the computation of ET throughout the Northeast, despite the large topographic het-erogeneity and climate of the region.

Alterações no Balanço Radiativo em Áreas de Pastagem e Floresta Obtidas por Meio de Imagens Orbitais MODIS (Changes in the Radiative Balance in Pastures and Forest Areas Through Orbital MODIS Images )

O presente trabalho tem por objetivo avaliar se alteracoes promovidas pela substituicao da vegetacao primaria (floresta) por pastagem, afetam o balanco de radiacao e podem ser detectadas por imagens geradas pelo sensor MODIS a bordo do satelite Terra. Para tanto, foi utilizada a metodologia convencionalmente denominada SEBAL, para o computo do saldo de radiacao instantâneo e de suas componentes, visando a precisao das estimativas atraves da validacao dos resultados a partir dos dados obtidos de duas torres experimentais, situadas na area de floresta e pastagem. Os coeficientes de determinacao (R2) encontrados, 0,81 (floresta) e 0,71 (pastagem) na estimativa do saldo de radiacao, demonstram a confiabilidade da tecnica empregada, a qual proporciona destacar padroes que diferenciam as respectivas coberturas do solo e concluir que a substituicao da vegetacao nativa por pastagem aumenta o albedo da superficie, alem de diminuir o saldo de radiacao o que pode impactar o clima das areas referentes a tal substituicao. A B S T R A C T The present study aims to evaluate whether changes introduced by replacing the primary vegetation (forest) by grazing, affect the net radiation and if it can be detected by images generated by MODIS sensor aboard of the Terra satellite. For this, was used the conventionally methodology called SEBAL, for calculating the instantaneous net radiation and its components, in order to estimate the precision through the validation of the results based on data obtained from two experimental towers, located in forest and pasture areas. The coefficients of determination (R2) found, 0.81 (forest) and 0.71 (pasture) in the estimation of net radiation, demonstrating the reliability of the technique, which provides emphasize patterns that differentiate the respective ground covers and to conclude that the replacement of native vegetation by grazing increases the surface albedo, and reduce the net radiation which can impact the climate of the areas relating to such replacement. Key-Words: albedo, vegetation, Amazonia, validation.