Variabilidade interanual do índice de vegetação no leste do Nordeste do Brasil no período de 1982-1999.

Abstract

The objective of the present study is the identification of spatial patterns, temporary correlations and NDVI fraction vegetation in homogeneous areas in the east area of the Northeast of Brazil. Annual time series of NDVI, with resolution of 5.5 Km x 5.5 km, obtained from AVHRR sensor on board of NOAA satellites, were used. Time series of annual rainfall for the period of 1982-1999, were also used. Temporary correlations and annual spatial patterns of IVDN were calculated through the technique of the Principal Analysis Components (ACP). Homogeneous groups of NDVI were obtained through of the method of K-means for eastern area for each selected state. Three homogeneous groups of NDVI for all the states were obtained, except for Rio Grande do Norte with two groups. For each homogeneous group the fraction of vegetated area was calculated using of the NDVI grid number and the associated state area. The obtained results showed that IVDN of the driest years was correlated better with first factors, the rainy years with the second factors and years around the climatological average with the third factors. In the 80’ decade, in most of the selected states, the vegetation fraction presented stability in the coastal area. On the other hand, during the 90’ a quite significant reduction of the vegetation fraction was detected close to a narrow coast area “perenifólia” forest and an accentuated increase of that fraction in the area seasonal forest (caatinga e agreste).