Seasonality of Pathfinder Avhrr Land Ndvi Data for Northeastern Brazil

The Normalized Difference Vegetation Index (NDVI) was used to characterize the seasonal variation of land cover over the Northeastern Brazil (NEB) with the NOAA/NASA Pathfinder AVHRR Land (PAL) data set. Twenty years of monthly spatial-aggregated NDVI climatology was determined by calculating lower, mean, and upper NDVI values using a 0.5 lat by 0.5 log grid cell size. The results indicated that the threshold NDVI values of lower and upper phenological activity are 0.103 and 0.771 over NEB, respectively. In this study it was also found that the distribution of NDVI frequency values ranged from 34% (peak centered at 0.3) to 51% (peak centered at 0.7) in May and from 40% (peak centered at 0.3) to 42% (peak centered at 0.7) in October. The seasonal variation of lower and mean NDVI values reflected a better discriminator of the changes of NDVI related to rainy and dry seasons.