By Clever Mafuta- SANF 04 no 12
The southern African region has been afflicted by poor growing seasons resulting from floods and prolonged mid-season droughts over the last four years. There is documented evidence of these events with droughts occurring more frequently than floods.
Scientists have even noted that the rate at which the droughts occur gives the feeling they are no longer a climatic abnormality but are part of the region’s rainfall pattern.
This calls for accurate forecasting that will assist farmers in planning for their agricultural season as it will save time and resources. Planning for agricultural seasons is a crucial factor in mitigating the impacts of weather extremes and sustaining food security. However, such planning becomes a challenge when gradual forward shifts in the on-set of the rains become a common feature.
The rainfall situation is compounded by the mindset of the ordinary farmer which has largely remained the same, with planting happening during the traditional but increasingly dry months of October and November.
Agricultural planning becomes more difficult when rainfall forecasts are given mostly as averages in areas with wide climatic variations. This is despite the basic understanding that rainfall variation has two important components. They are the spatial (space) and temporal (time) variabilities.
While the previous seasons have to a large extent been affected by the El Nino phenomenon, the current 2003/04 season has largely been predicted to be a normal one. This is notwithstanding the fact that there are some temporal and spatial variability to it.
This season’s regional outlook indicated normal rainfall for much of Zambia, Malawi, Zimbabwe, Botswana, Mozambique, Swaziland, Lesotho and South Africa. However, the situation on the ground is different with much of the rains having started late.
According to the SADC Regional Food Security Programme Agromet Update, the period up to the first 10 days of December were characterized by dry conditions across most of the southern half of southern Africa. Satellite-derived rainfall estimates suggest that most areas in Botswana, Lesotho, southern Malawi, southern to central Mozambique, Namibia, South Africa, southern Zambia and Zimbabwe received little to no rainfall. Compared with the average scenario, the rainfall season should have started in earnest then, but up to early December the season had not had a good start.
In the northern half of southern Africa, many areas had received good rains by December. This excludes eastern Tanzania where dryness continued to aggravate the soil moisture levels.
Exceptions were over eastern Zambia and Malawi which had above normal rainfall throughout the season. Botswana and north-western South Africa had below normal rainfall throughout that season.
Spatial variability of the anomalies also existed within the southwestern sector covering southeastern half of Namibia, western Botswana, northwestern South Africa and the northwestern half of Mauritius having relatively below normal conditions as compared to normal.
In 2002/03 spatial and temporal variabilities were also quite clear. The northern part of the SADC region covering DRC, United Republic of Tanzania, much of Angola, northern Zambia, northern Mozambique and northern Malawi, which always receive good rains early in the season, received normal to above-normal rainfall for the period October to December. The rest of the region experienced normal to below normal rainfall.
Bearing in mind that the region’s climatic outlook monitoring systems have become sophisticated, rainfall forecasting should be more specific to time and space. Such time and area forecasts are important in saving resources, as well as ensuring effective agricultural planning. (SARDC – SADC Today)
