Temporal and Spatial Distribution of Savanna Fires in Senegal and the Gambia, West Africa, 1989-90, Derived From Multi-Temporal AVHRR Night Images

Quantitative data on fire regimes from the world's savannas have previously been difficult to obtain due to logistical and scientific reasons. This study addresses the issue for Senegal and The Gambia, West Africa. A bispectral satellite image based method for fire detection has recently been improved and made semi-automatic to provide information on fire regimes of savannas. The method uses thermal night time data from the Advanced Very High Resolution Radiometer (AVHRR) onboard the National Oceanic and Atrnospheric Administration (NOAA) series of weather satellites. Twenty-six near cloud-free AVHRR images have been classified using this method. Though they constitute a small temporal sample, some features of the seasonal periodicity and spatial variations of the region are suggested. Variations in firectivity at the four daily NOAA satellite passing times were recorded from a small field survey in The Gambia, and compared to data from the satellite images. Established relationships between reiative fire activity and data from the various NOAA passes have been used to estimate the maximum daily fire activity at the afternoon passing time. The seasonal variations for the whole study area and regions within are suggested by the estimated maximum values at the twenty-two dates. The locations of fire events in relation to locations of human activities and fuel loadings are examined and a brief summary of the main factors that regulate burning and fire regimes is given.