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close this bookSPORE Bulletin of the CTA No. 41 (CTA Spore, 1992, 16 p.)
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Radio: the weather wavelength

Recent advances in meteorology mean that radio is set to become one of the prime tools in communicating weather forecasts to rural dwellers.

Sahelian agriculture is very much at the mercy of the weather. The average annual rainfall is between 30 and 75cm and crop plants however well adapted they appear to be to this sort of environment, live on a meteorological knife-edge. Every crop, from tubers such as cassava or sweet potato in the south, through cereals such as miller and sorghum in the centre, to the pasturelands of the nomadic flocks and herds on the edge of the desert, is stretched to the limits of its endurance. The slightest blip in the weather pattern can be fate]. Drought is a catastrophe which affects a whole region, but for the peasant farmer a small disturbance in the weather could be just as drastic, even though it may not show up on the national statistics.

Accurate prediction is equally important, whether one is governing a country or managing a small patch of land. In agriculture, the most valuable attribute is to know what the weather will do at any given time; this is true for governments which have to plan future policy as well as for farmers whose daily round is the rhythm of the land itself, sowing, weeding, harvesting, drying, storing.

Thanks to satellite technology, to highly developed networks of ground observation and to the computerization of statistical data, the Sahelian states now have 'instrument panels' which allow them to plot the progress of weather in ten-day stretches. The various early-vvarning systems are nowadays extremely reliable, even if not exactly real-time. If, for example, on a given date, a certain level of rainfall has not been attained, then one can predict a measurable food shortage that year in that particular area.

Plotting progress

True weather forecasting, however, is not quite so accurate; but it is what the peasant farmer needs as he stands watching the cloud on the distant horizon, wondering whether it will bring rain for his crops.

The Sahelian climate is governed by the northward movement of the Inter-Tropical Convergence Zone (ITCZ) and its subsequent return southward and therefore seems, on the face of it, very simple. Huge cloud masses appear, vast enough to cover several countries, and their movement can be charted by satellite; but they do not necessarily bring rain, and any precipitation from these masses of humid air is very much a matter of chance - a localized phenomenon which science has not yet been able to predict with accuracy.

"We can't talk about proper forecasting: the most we can predict is the likelihood of rain," an agrometeorologist explained last May to a seminar in Bamako. He went on: "We can be 90% accurate 24 hours ahead, but the accuracy drops to 50% 48 hours ahead. Three days ahead and we're more likely than not to be wrong."

Forecast or analysis?

Two questions arise from this: firstly, can this information be transmitted to farmers within the 24-hour period so that they can take advantage of it? Secondly, is delayed information on previous rainfall of any use to the farmer?

The answer to the first question is still mainly "no". A seminar on "Agrometeorology and Rural Radio" organized in Bamako, Mali, by CTA and the World Meteorological Organization (WMO), supported by the FAO, heard that there is still a long way to go if the information provided by national meteorological services is to be processed, expressed in an appropriate language and broadcast instantly to peasant farmers. Only two of the nine CILSS (Permanent Interstate Committee for Drought Control in the Sahel) states represented had established a good liaison between rural radio journalists and the weather-forecasting services.

The MWG (Multidisciplinary Work Groups) to forge links between journalists, meteorologists and the various sectors concerned (crop-growing, pastoralism, food security etc) are gradually being formed in an attempt to get technical and media staff to agree on what tomorrow's agrometeorological forecasting system should be.

The response of the seminar to the second question was more positive: retrospective information can be of use to agriculture. Although it is still in an experimental phase, it can be a helpful tool in decision-making by making available old agrometeorological data. Farmers taking part in pilot projects now know when to sow, weed or attack pests in optimum conditions, thanks to local data broadcast by radio.

The experience of various Sahelian countries suggests that these pilot schemes could become widespread, and that farmers will gradually learn to use this new tool to their advantage. Information has become as important as agricultural machinery and rural radio will have to play a role of the first magnitude in its development.