On the use of NDVI for estimating rainfall fields in the Kalahari of Botswana

This article presents the results of an experiment to estimate rainfall from the normalized difference vegetation index (NDVI). The study was carried out in the semi-arid region of south and southern Botswana, principally the Kalahari Desert, where few rainfall-reporting stations exist. A statistical regression between NDVI and rainfall is developed for four areas with diverse soil conditions. These are used to estimate rainfall at an independent station or group of stations. The estimates reliably capture both the seasonal cycle and inter-annual variability. These regressions are used to produce a map of mean annual rainfall for the period 1982 to 1993, based on NDVI data, for the region 22 to 27 degrees S and 20 to 26 degrees E. The estimates are verified using all data available in the Meteorological Services' archive for these years. (C) 1997 Academic Press Limited.