Monitoring Drought Using Coarse-Resolution Polar-Orbiting Satellite Data - Monitoring and Predicting Agricultural Drought: A Global Study - page 67

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[67],

Line
——
0.0
——
Long
PgEn

Figure 5.6 Relationship between July-October NDVI and rainfall over West Africa, 1980-97
(fr om Tucker and Nicholson, 1999).

[67],

spatial resolution), the complexity of crop mixtures with surrounding veg-
etation types, and the small farm sizes that dominate the African land-
scape. Many major organizations, however, operationally use NDVI data
to monitor drought and famine in Africa, such as the Food and Agricultural
Organization's Global Information and Early Warning System (GIEWS;
http://www.fao.org/giews/), the U.S. Agency for International Develop-
ment's Famine Early Warning System Network (FEWSNET; http://www.
fews.net/; chapter 19), and the U.S. Department of Agriculture's Foreign
Agricultural Service (USDA/FAS; http://www.fas.usda.gov/pecad/pecad.
html). In all of the following examples for the Sahel, East Africa, and south-
ern Africa, the monthly NDVI data for 20

+

years were used (Tucker, 1996;
Anyamba et al., 2001, 2002; Los et al., 2001).

Th e Sahel

Prolonged and severe droughts occurred in the Sahel region of Africa in the
1970s and 1980s (Tucker et al., 1983, 1986; Hielkema et al., 1986; Justice
et al., 1986). These droughts were monitored by comparing monthly NDVI
values with the long-term means. Figure 5.7 shows reduction in NDVI
values on account of reduced precipitation for Mali in the Sahelian region
of Africa.