Satellite recorded vegetation response to drought in brazil

A normalized difference vegetation index (NDVI) derived from satellite data is used to study drought evolution in the South American continent. National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) data are used to produce NDVI maps for the South American continent during the period from 1 August 1981 to 30 June 1987. A 15‐day maximum‐value composite procedure is used to partially eliminate cloud contamination and atmospheric attenuation. Vegetation response to drought is studied by inspection of the temporal and spatial evolutions of monthly drought area maps, which are delineated by NDVI values lower than 0.22. Drought area evolution patterns over the continent during the period of 1981–1987 for the months of May and September are discussed. The results show a well‐defined regional dependence of the drought area variability. Drought dynamics analyses are performed for the dry year of 1982–1983 and for the wet year of 1984–1985. This information is used to discuss the relationship of the drought pattern with the El Niño‐Southern Oscillation (ENSO). Emphasis is given to the north‐eastern region of Brazil, for which the relative drought area coverage was computed to demonstrate its high interannual drought variability. An intensification of this behaviour during the 1982–1983 ENSO event was identified in this area. The results indicate the potential use of satellite NDVI imagery to monitor drought occurrences as well as to study climatic variability on regional and continental scales.