Navegando por Assunto "NDVI"

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Acesso aberto (Open Access)
Análise da variabilidade espaço-temporal da precipitação e focos de calor em vegetação na ilha Hispaniola.
(Universidade Federal do Pará, 2020-08-07) PRÉVOIR, Ermano; LIMA, Aline Maria Meiguins de; http://lattes.cnpq.br/6572852379381594; https://orcid.org/0000-0002-0594-0187; SOUZA, Everaldo Barreiros de; http://lattes.cnpq.br/6257794694839685; https://orcid.org/0000-0001-6045-0984
Insular or island countries located in Central America and the Caribbean are vulnerable to variability and climate change. This work presents a contribution to climatological studies, particularly of the Hispaniola Antilles of the Caribbean Sea, formed by the countries of the Republic of Haiti and the Dominican Republic, covering an area of 78 thousand km². Based on the analysis of precipitation from the CHIRPS base with high spatial resolution, a bimodal climate pattern was found in Haiti and the Dominican Republic with the first rainfall peak occurring in May and the second in September/October. The dry regime occurs from January to March. The spatial patterns of the climatological maps and the correlation analysis indicated that the seasonal precipitation regimes of the Antilles are directly influenced by the configuration of the SST and the trade winds in the Caribbean Sea over the Atlantic Ocean, with the main maximum of the second semester being explained by the presence warmer TSM (above 29C) and by the cloudiness band associated with ITCZ during its most boreal position. The quantitative assessment of the correlations (simultaneous and lagged) between rainfall data and vegetation indexes and vegetation fires, as well as the integrated analysis of the mapping of these variables over the Hispaniola territory, allowed to establish consistent relationships in the dynamics of climate, vegetation and fires. Dominican Republic has much higher numbers of fires when compared to those in Haiti, with the highest frequency of events taking place from January to April, when the dry regime over the Antilles prevails. Conversely, during peak rainfall in the second half of the year, fires are minimal and are concentrated in the months from August to December. As for the vegetation indices, there is a certain direct relationship with the climatic regime, so that the higher NDVI are observed into regions containing maximum precipitation and vice versa.
Acesso aberto (Open Access)
Análise temporal da cobertura vegetal de um fragmento da RPPN Seringal Triunfo, Ferreira Gomes - Amapá
(Universidade Federal do Pará, 2021-12-27) SCHNEIDER, Juliana Cristina; GODOY, Bruno Spacek; http://lattes.cnpq.br/4036516695601666; https://orcid.org/0000-0001-9751-9885
The construction of dams became necessary for national development, the Amazon region, for having a great hydro-energetic potential, was also used for the construction of these projects. River Araguari's hydrographic basin has three hydroelectric dams (Coaracy Nunes, Ferreira Gomes and Cachoeira Caldeirão) built in its middle course, in the municipality of Ferreira Gomes, however the construction generated several problems, such as loss of territoriality, difficulties in subsistence of villages and the environment modification. However, in 1998, there was the enactment of the Seringal Triunfo National Heritage Private Reserve, which aims to conserve biodiversity. Therefore, there is a need for studies aimed at improving the knowledge of vegetation cover, which have occurred since the enactment of the RPPN. In this sense, the present study sought to understand whether there were changes in the vegetation cover in the RPPN from 2000 to 2015, after its approval and with the construction of UHE Ferreira Gomes and Cachoeira Caldeirão. For this, remote sensing data were used. Twelve images obtained from the TM/Landsat-5, ETM+/Landsat 7 and OLI/Landsat-8 satellites were used, delimiting the study area with the creation of two polygons (buffer), one located within the RPPN and another adjacent with approximately the same size. Digital processing techniques were applied to these images with the aid of pixel counting software. The Normalized Difference Vegetation Index (NDVI) was calculated, making it possible to obtain the median. The obtained results show that the image processing allowed differentiate its constituent elements (vegetal cover and exposed soil). The calculation of the NDVI medians, for the scenes between the years 2000 to 2015, in the area located within the RPPN ranged from 0,37 to 0,64 and the medians of the adjacent area ranged from 0,29 to 0,63, thus, the statistical analysis showed no relationship with the years (F1,10 = 0,02 and P = 0,87), indicating that during the analyzed period there was a stability in the vegetation cover, the same occurred for the adjacent area (F1,10 = 0,11 and P = 0,74). This stability in the area of the RPPN may be related to the role it plays in nature conservation and in the adjacent area to the stagnation of population growth in the municipality. The use of images from remote sensors proved to be a very valuable tool for the present research, even without carrying out an on-site visit, it was possible to calculate the NDVI. Therefore, it is recommended for future work to analyze the NDVI from years prior to 2000, that is, years prior to the approval of the RPPN, as well as on-site visits, for the validation of the components observed in the NDVI, for the NDVI classification to the studied locality.