SEASONAL DISTRIBUTION OF AFRICAN SAVANNA FIRES

SAVANNAS consist of a continuous layer of grass interspersed with scattered trees or shrubs, and cover approximately 10 million square kilometres of tropical Africa1,2. African savanna fires, almost all resulting from human activities, may produce as much as a third of the total global emissions from biomass burning3. Little is known, however, about the frequency and location of these fires, and the area burned each year4. Emissions from African savanna burning are known to be transported over the mid-Atlantic, south Pacific and Indian oceans5,6; but to study fully the transport of savanna fire emissions, the spatial and temporal variations in regional savanna burning and the seasonality of the atmospheric circulation must be considered simultaneously. Here we describe the temporal and spatial distribution of savanna fires over the entire African continent, as determined from night-time satellite imagery. We find that, contrary to expectations, most fires are left to burn uncontrolled, so that there is no strong diurnal cycle in the fire frequency. The knowledge gained from this study regarding the distribution and variability of fires will aid monitoring of the climatically important trace gases emitted from burning biomass.