Click here to see a larger image and a comparison with previous years. The Normalised Difference Vegetation Index (NDVI) data is calculated from measurements from NOAA meteorological satellites. The NDVI image provides an indication of the vigour and density of vegetation at the surface. Images of NDVI are sometimes referred to as "greenness maps" since they represent the vegetative vigour of plants. The data are represented as coloured maps, with colours representing the density of vegetation.

The primary use of these images is to compare the current state of vegetation with previous time periods, for example the same time in an average year to detect anomalous conditions. In this case the 'normal' situation is taken as the average measurements over the period 1995 to 1999. Hence yellow and red colours indicate reduced vegetation this year compared to 'normal', whereas green colours indicate increased vegetation this year compared to the 'normal'.

The bottom image clearly shows the reduction in vegetation growth at this stage in the year compared to the average, with yellow and red colours apparent, especially over Zimbabwe, Zambia and DRC.