Mean and inter-year variation of growing-season normalized difference vegetation index for the Sahel 1981-1989

Abstract

Images are presented that show the mean and coefficient of variation of nine years (1981-1989) of NOAA advanced very high resolution radiometer (AVHRR) normalized difference vegetation index (NDVI) data for the growing season (July-October) in Africa, north of the equator. The sequence of years includes the very dry years of 1984 and 1985 and also some wetter years such as 1988 and 1989, although the entire period was drier than the long-term means that include the wetter 1960s (Nicholson et al. 1988). The images were prepared from monthly maximum value NDVI composites derived from daily NOAA AVHRR global area coverage (GAC) data. Compositing and cloud screening techniques have been applied to the data as described by Holben (1986). Typically three or four orbits were used per day giving approximately 100 per month. In all approximately 3600 orbits have been processed to create the images that are presented.