Satellite monitoring of fire in the EXPRESSO study area during the 1996 dry season experiment: Active fires, burnt area, and atmospheric emissions

Fire activity in central Africa was monitored with NOAA advanced very high resolution radiometer (AVHRR) satellite imagery, acquired in situ during th e 1996 dry season campaign of the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO). The extent of the area affected by fire was estima ted with a contextual active fire detection algorithm, and with a burnt are a mapping approach, based on multiple fuzzy thresholds. The latter was cons idered to produce more accurate results. In a study area of 2 x 10(6) km(2) , and during a 5-week period, the areas affected were estimated at 112,578 and 525,820 km(2) by the active fires and burnt area algorithms, respective ly. Biomass densities, combustion factors, and emissions factors for Sudani an savanna, Guinean savanna, and dense tropical forest vegetation types wer e obtained from the literature, and used to estimate biomass burnt (228-371 Tg), and pyrogenic emissions of aerosols (1.8-2.6 Tg) and of the trace gas es CO2 (374-609 Tg), CO (29.2-39.0 Tg), CH4 (2.05-2.73 Tg), and NOx (1.1-1. 4 Tg). Because of its high biomass density, the tropical forest was a major source of atmospheric emissions, in spite of the relatively small extent o f area burnt in this ecosystem. This highlights the need for particularly a ccurate estimates of area burnt, biomass density, combustion factor, and em issions factor for the dense tropical forest, as well as the potential for a significant increase in regional pyrogenic emissions as a consequence of deforestation.