THE OUTPUTS described below have different levels of "added value".
The most synthetic of all is no doubt the crop yield map, an
essential tool for decision making at the national level. Based on
such maps, governments can calculated district and provincial yields
and production, and decide whether food production is adequate.
Necessary action can thus be taken in advance.
Crop yield map
A crop yield map is an extremely synthetic and useful product. Its
simplicity hides the fact that complex analyses, and a very sizeable
amount of data, have been used in its preparation. It clearly shows
areas of high and low yields, and constitutes the basis for
regional/provincial production estimates.
Crop condition map
Next to maps based on reports provided by field observers, NDVI is one
of the tools that can be used to map out crop condition. The two maps
below show the same area during two rather different years: a dry year
(1984) and a wet year (1988). The difference is striking in northern
Senegal and Niger.
There are many different monitoring indicators. Most of them rely on the
comparison of some current value with average or "normal"
conditions. The best known indicator of this type is rainfall departure
from normal. Below, two examples are illustrated: departure of Cold Cloud
Duration from the average of several recent years, and a synthetic image
showing the difference in cereal yields in Niger between 1995 and 1996.
For further information on Agrometeorological
Crop Forecasting, contact the FAO Agrometeorology Group (e-mail: