The United States is taking a long step toward meeting one of the most urgent needs of Africa and the third world: an accurate early-warning system to forecast famine. Based on new computer technology, the US is about to combine data from a US polar-orbiting satellite and from US and local ground reports into monthly analysis-and-prediction packages of African rainfall, weather, crop, and range-land conditions.
US officials claim that the data packages, put together by 30 analysts in Washington and more in Columbia, Mo., can forecast the size of harvests 30 to 60 days in advance, enabling emergency relief plans to be laid if necessary.
The data packages are to be mailed to US Agency for International Development (AID) missions across the eight countries of the Sahel, and in Ethiopia, Somalia, and Sudan, then updated every 10 days by telex. African officials are to be trained in evaluating the data.
AID officials hope that in time the new data will be accepted as impartial and authoritative, thus filling a forecasting gap in international relief work.
The innovative key lies in satellite color pictures newly formed from existing electronic data by computer image enhancers on the ground.
``The images measure vegetation and its vigor,'' says Paul Krumpe, technical adviser in the office of foreign disaster assistance at AID.
``You can actually see the greening of Africa as rain falls . . . and we measure cloud heights, densities, and color as well to determine that rainfall.''
The polar-orbiting satellite, operated by the National Oceanographic and Atmospheric Administration (which, among other things, administers the US weather service), crosses Africa every few hours. Its sensors can focus on ground areas less than a mile wide. The better-known Landsat satellite covers Africa only once every 18 days.
Estimated AID budget for the next 18 months for this operation: $2 million. The first packages, with data for the month of June, went to AID missions in Africa on July 15 for evaluation. The first full-scale distribution comes Aug. 15, covering July, a month which has seen widespread rainfall and planting.
Involved in the plans are 15 US government agencies which met at the US State Department July 15-16, and plan to meet again in September.
The US step is welcomed -- with some reservations -- by the UN Food and Agriculture Organization (FAO) in Rome, which has its own early-warning system in place (based partly on the European Space Agency's Meteosat satellite) and is training a number of African governments to interpret the results.
``Yes, the US imagery is new and valuable,'' says a veteran FAO official. ``We know what the US is doing: in fact, we use its existing data in our own early-warning bulletins.
``Remember, though, that satellite imagery is only one tool for predicting. It can be overvalued.''
To FAO, data systematically collected on the ground is still at the heart of all predicting.
But ground data -- rainfall statistics, for example -- is the Achilles' heel of both US and UN warning systems, experts say. In countries as vast and illiterate as Sudan and Ethiopia, no one really knows how much rain has fallen. Few accurate comparisons can be made with years past. The same is true of the Sahel region.
UN experts also warn that US, UN, and local-government data now needs to be coordinated properly in Africa and in the West.
``The ultimate audience is the African policymaker as well as the Western donor,'' one UN expert warns. ``He mustn't be overwhelmed with data he doesn't understand.''
More caveats come from private aid agencies. In Britain a spokesman for the Oxfam relief organization commented, ``Yes, early warning is fine -- but only policymakers can act on the warnings. We can shout ourselves blue in the face that a famine is coming, but someone has to listen.
In Washington, analysts receive electronic data from an instrument called AVHRR -- Advanced Very High Resolution Radiometer -- on board the polar-orbiting satellite.
AVHRR has been sending the data along with other signals since sent up with the satellite six years ago to monitor rainfall patterns.
Only recently, according to Krumpe, have scientists figured out how to ``enhance'' the data into color images through a process called ``ratio-ing.''
Besides the imagery, the new US data packages will include cloud-pattern analysis, rainfall data from the UN World Meteorological Organization, press and radio reports collected by the US Foreign Broadcast Information Service, and reports from AID missions in Africa.
What happens if the polar-orbiting satellite breaks down?
``We are making plans for a backup to be launched,'' says Krumpe. ``We also have a spare geostationary satellite we are moving into position over Africa.''
US agencies involved include AID, the National Aeronautics and Space Administration (NASA), NOAA, National Science Foundation, the White House Office of Science and Technology Policy, the Geological Survey, and the Departments of State, Defense, Agriculture, and Energy.
Krumpe sees the early-warning system as part of a wider US effort to predict disasters of other kinds: tidal waves, volcano eruptions, floods, cyclones, landslides, and more.