inventory of quantity and type of clouds over the region (McDonald and Hall, 1980), and the second, a quick analysis of the extent and rate of growth of green vegetation over large areas. The major question posed by this proposal was whether data from Earth observation satellites could be combined with sparse data from other sources to design a system and methodology for credible crop modeling and yield predictions in this environment. Several U.S. government agencies therefore organized a pilot project to determine the feasibility of this approach.

The project, which was conducted from 1979 to 1986, had three objectives: (1) detection and monitoring of droughts, (2) crop modeling condition assessment, and (3) prediction of crop yield potential (LeComte, 1994). The crops that were monitored included cowpeas, maize, millet, peanuts, and sorghum. These objectives were interrelated in that water is the most critical limiting factor for crop growth in Africa's Sahel and Horn regions. Precipitation is usually the only source of water for growing crops in this area. In fact, average depth to groundwater in the region is so great that groundwater as a source for crops is not a serious alternative. The development of a capability to determine precipitation and its variability over the region in near real time could be expected to improve significantly the assessment of crop and yield potentials, both spatially and temporally.

The U.S. Agency for International Development provided most of the financial support, and the U.S. National Oceanic and Atmospheric Administration (NOAA) was the executing agency of the project (referred to as the "NOAA project" below). The Climate Impact Assessment Division (CIAD) of NOAA's Assessment and Information Services Center (AISC) was responsible for overall management. Appropriate agencies from each of the participating Sahelian and Horn countries provided valuable input to and collaboration with the project.

Major features of the NOAA project included the development of a plan of action or implementation plan and of a management structure and organization to implement the plan. Neither of these tasks was easy or clear-cut. In the formulation of each planning task, many assumptions had to be made, not the least of which was that adequate ground observation data could be obtained in a timely fashion. Another hope, if not an assumption, was that adequate in-country technical support for each of the participating sub-Saharan countries would be available with a minimum of constraints in the flow of essential information. Another feature, perhaps unique to this project, was the global perspective, which necessitated the integration of disparate global, national, and local data sources. This integration also required free flow of data and information across many international boundaries.

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