SATELLITE-OBSERVED VEGETATION AS AN INDICATOR OF CLIMATE VARIABILITY OVER SOUTHERN AFRICA

The satellite-derived normalised difference vegetation index (NDVI) of fers new opportunities to assess the impact of year-to-year climate fl uctuations. In this study the NDVI is mapped over southern Africa for the period 1981-1994. Sharp upward and downward trends follow the cycl e of summer flood and drought. January to March NDVI values are correl ated at +0.82 with harvested maize yield for the North West Province o f central South Africa. Departures of late summer NDVI from the histor ical mean illustrates the distribution and intensity of the influence of the Southern Oscillation, in alternating seasons of vegetative grow th and depletion. The first principal component of the NDVI field time series contains a broad signal covering all of Africa south of 15 deg rees S, and appears related to the low frequency component of the glob al El Nino phenomenon.