RESUMOO saldo de radiação é um importante componente do balanço de energia e tem grande relevância em estudos de evapotranspiração em áreas irrigadas e em bacias hidrográficas. Obteve-se, através do estudo, a estimativa do saldo de radiação à superfície terrestre, mediante imagens multiespectrais do Mapeador Mapping net radiation using Landsat 5 imagery and digital elevation model ABSTRACT Net radiation is an important component of the surface energy balance in studies of evapotranspiration of irrigated crops and in evaporation of hydrological basins. The objective of this research was to determine the surface radiation balance, by using multispectral imagery of the Thematic Mapper (Landsat 5 satellite). In this study the SEBAL (Surface Energy Balance Algorithm for Land) and DEM (Digital Elevation Model) were used in order to correct the albedo and vegetation indices under the influence of the slope aspects were used for each study area. TM (Thematic Mapper) imageries were used for two different dates (December 4, 2000 and October 4, 2001). The calculations were accomplished with and without use of the DEM. The land surface temperature and albedo values with DEM were larger than without DEM in both years, for two selected areas. Results also show that for obtaining net radiation based on imagery of the TMLandsat 5 the topographical effects of the study area must be considered.
ABSTRACT:The aim of this study was to identify areas susceptible to drought and under desertification in the Brazilian Northeast, more specifically in the states of Alagoas, Pernambuco, and Sergipe. The study was based on the 2000-2014 time period, relative frequency, Vegetation Condition Index (VCI) dataset derived from MOD13Q1 products (vegetation indices derived from the Moderate Resolution Imaging Spectroradiometer sensor). The areas located within the desertification nucleus of Cabrobó, in the southwestern of Pernambuco and surrounding the Águas Belas municipality were considered susceptible to drought and desertification. Some municipalities in the countryside of Alagoas showed a very low relative frequency of VCI data (45-50%), and occurrence of areas between 55-60%.Tthe Sergipe state presented a relative frequency VCI data around 50% only in the Poço Verde municipality. Among the areas with low rates of VCI and the most frequently identified in this research, therefore, with greater frequency of droughts, the Southwestern and the Southern Pernambuco hinterlands were not considered as pilot areas by MMA (Brazilian Environment Ministry) in its desertification studies and were included as susceptible for desertification in this study. The results suggest the use of this methodology to subsidize formulations of public policies with application in land use and land cover studies or sustainable development and environmental risk analysis.
Artigo recebido em 16/06/2010 e aceito em 09/09/2010 R E S U M O O trabalho proposto estima, mediante dados de imagens multiespectrais do Landsat 5-TM, a temperatura da superfície terrestre da cidade de Maceió, relacionando-os com a malha urbana. Maceió nos últimos 30 anos teve seu crescimento areal intensificado, o que resulta na substituição de áreas verdes por uma zona urbana edificada, alterando o relevo, impermeabilizando o solo, e em consequência, a diminuição da participação do fluxo de calor no solo do balanço de energia na superfície e o aumento do fluxo de calor sensível, responsável pela sensação térmica sentida. Portanto, mudanças locais causadas por edificações e ocupações inadequadas provocaram alterações no conforto urbano. As imagens utilizadas são compostas por sete bandas espectrais, referentes aos dias 11 de junho de 1990, 21 de setembro de 1998 e 03 de setembro de 2003. Os cálculos foram realizados com a utilização do software ERDAS 8.5. A temperatura da superfície terrestre estimada foi maior para o ano de 1998 sendo de 26,96°C seu valor médio e para os anos de 1990 e 2003 foi praticamente a mesma, sendo de 24,19°C e 24,90°C, respectivamente. Palavras-chave: Sensoriamento remoto, temperatura da superfície terrestre. Instantaneous Values of Surface Temperature in Maceió-AL Using Satellite Images TM/Landsat 5 A B S T R A C TThe considered work esteem, by means of data of multispectral images of the Landsat 5 -TM, surface temperature surface of the city of Maceió relating them with the urban mesh. Maceió, in last the 30 years, it had its intensified areal increasing, that is, the substitution of green areas for a built urban zone, modifying the relief, waterproofing the ground, thus diminishing the participation of the flow of heat in the ground of the rocking of energy in the surface and increasing the flow of responsible sensible heat for the felt thermal sensation. Therefore, local changes caused by constructions and inadequate occupations had provoked alterations in the urban comfort. The used images are composed for seven referring spectral bands to days 11 of June of 1990, 21 of September of 1998 and 03 of September of 2003. The calculations had been carried through with the use of software ERDAS 8.5. The temperature of the terrestrial surface estimate was bigger for the year of 1998 being of 26.96°C the average value and for the years of 1990 and 2003 she was practically the same one, being of 24.19°C and 24.90°C, respectively. Keywords: Remote sensing, surface temperature. IntroduçãoNos últimos 30 anos, o município de Maceió teve o crescimento da malha urbana intensificado, ou seja, a substituição de áreas verdes por uma zona urbana edificada. Nos centros urbanos, quase tudo é artificial; e, quando é algo natural, apresenta sempre variações e modificações provocadas pela ação humana. O clima das metrópoles , o chamado clima urbano, um tipo específico de microclima, constitui um exemplo disso. Nas grandes cidades faz mais calor e chove um pouco mais do que nas áreas rurais circunvizinhas...
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