Satellite monitoring of vegetation fires for EXPRESSO:: Outline of activity and relative importance of the study area in the global picture of biomass burning

The satellite monitoring of vegetation fires for the International Global Atmospheric Chemistry (IGAC) Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO) was designed to assist the assessment of the fluxes of trace gases and aerosols emitted by savanna fires that occur during the dry season in Central Africa. It is of particular interest that the study area covers the transition zone between the savanna and the forest domains. Satellite remote sensing is the only technology that allows consistent data collection of the spatial and temporal distribution of fires at the scale required by the EXPRESSO experiment. A portable monitoring system was developed and operated in Central Africa for the in situ, real-time acquisition and processing of National Oceanic and Atmospheric Administration-advanced very high resolution radiometer (AVHRR) imagery during the EXPRESSO dry season field campaign, which lasted from October 1, 1996, to December 2, 1996. One AVHRR scene per day was processed to locate active fires and burnt areas. These results are compared with our daily global maps of vegetation fires derived from the International Geosphere-Biosphere Programme-Data and Information System Global AVHRR data set for the period April 1992 to December 1993. This comparison shows the EXPRESSO fires in the context of the African continent and of the total global fire activity. The EXPRESSO study area is part of one of the largest fire belts observed in Africa, and even over the globe, spreading from Senegal to Ethiopia. This study also shows a big increase in the number of fires in 1996 compared to 1993, from a total of 39,500 fire pixels detected in November 1993 to 124,500 in November 1996. We also show that the November period corresponds to a minimum of the global fire activity: only 3% of the fires detected during a complete year were detected during this month. Moreover, the number of fires detected in this particular month was 28% of those detected during the annual peak period observed in July-August. Current activity is focusing on the implementation of the World-Fire-Web network: A system for globally mapping vegetation fires.