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INSTITUTO NACIONAL DE PESQUISAS ESPACIAIS (INPE) (1999)

ANÁLISE ESPAÇO TEMPORAL DE ÍNDICE DE VEGETAÇÃO

Alves Barbosa Humberto

Titre : ANÁLISE ESPAÇO TEMPORAL DE ÍNDICE DE VEGETAÇÃO AVHRR/NOAA E PRECIPITAÇÃO NA REGIÃO NORDESTE DO BRASIL EM 1982-85

Auteur : Humberto Alves Barbosa

Université de soutenance : INSTITUTO NACIONAL DE PESQUISAS ESPACIAIS (INPE)

Grade  : Mestrado em Sensoriamento Remoto 1999

Résumé
This work analyzes the spatial and temporal variation of Normalized Difference Vegetation Index (NDVI) and precipitation over the Northeast region of Brazil (NEB), between 1° to 18°S and 35° to 47°W. Studied were the dry years of 1982 and 1983 and the rainy years of 1984 and 1985, covering the intense El-Niño/Southern Oscilation (ENSO) event of 1982-83. The following parameters were used : monthly NDVI mean values 17,000 windows with 3 x 3 pixels each, originated from the Advanced Very High Resolution Radiometer (AVHRR) images of the NOAA satellites with a resolution of 7.6 km in the Global Area Coverage (GAC) format, from the NASA/GIMMS archives ; monthly rainfall data from 1,850 stations of "Superintendência de Desenvolvimento do Nordeste" (SUDENE) and ; monthly means of Sea Surface Temperature (SST) in grid points with 2° spacing, also derived from the AVHRR and prepared by the National Meteorological Center (NMC). Ten test-areas representing prevailing and different phitophysiognomies of the region were used for the temporal analysis. The spatial analysis was based on a grid of 5,571 precipitation data points spaced by 0.25° in latitude and longitude, interpolated from the original rain-gauge measurements. In relation to previous NEB studies, the subdivision of the vegetation in classes and the use of correlations with time lags were introduced. The results showed that : i) NDVI and precipitation monthly data follow similar patterns on temporal and spatial basis, being statistically correlated, where the NDVI can depict the precipitation regime in periods of unusual drought or rain in the NEB ; ii) the best correlation was found between the combined precipitation of two consecutive months with the NDVI and the first of these two months ; iii) there was an NDVI increase in the rainy season also for the extremely dry year of 1983 ; iv) NDVI and precipitation better represented the vegetation hidric potential in the form of a ratio, or Rain Greenness Ratio (RGR), than separately, and ; v) the largest NDVI variation occurred for the urban area class. These results indicate a strong application potential to regional evaluations of areas under or recovering from strong droughts in the NEB, particularly if combined with in-situ data. The continuation of this research using orbital data with better spatial resolution is recommended.

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