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[72],
Line
——
0.9
——
Norm
PgEn
[72],
Fig
ure 5.10
Spatial variation in NDVI anomaly across East Africa during the critical growing
sea
son of 1984.
with associated low NDVI values (typically
0.2). During 1991-93, NDVI
values over the growing season were lower than their long-term means, in-
di
cating the prevalence of drought conditions. The NDVI during the 1992-
93
period was below the long-term average. In 1992, the region received
be
low-normal rainfall, causing region-wide drought conditions with NDVI
an
omalies reaching 80% below normal.
∼
Fu
ture Research Needs
The SWIR portion of the electromagnetic spectrum is a region over which
leaf water content influences the reflectance response from vegetation can-
opies, enabling one to assess the drought status of crops and vegetation
(Tucker, 1980a). However, the operational use of the SWIR region for
drought studies has been restricted by problems in separating the effects
of canopy structure and geometry from those of water status. Ceccato et
al. (2001) have shown that by combining the NIR and SWIR data into
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