Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 4 2005 10.5194/acpd-5-4641-2005 http://www.atmos-chem-phys-discuss.net/5/4641/2005/ http://www.atmos-chem-phys-discuss.net/5/4641/2005/acpd-5-4641-2005.html http://www.atmos-chem-phys-discuss.net/5/4641/2005/acpd-5-4641-2005.pdf 4641 4677 2005-07-12 Screening the ESA ATSR-2 World Fire Atlas (1997–2002) B. W. Mota J. M. C. Pereira D. Oom M. J. P. Vasconcelos M. Schultz Departamento de Engenharia Florestal, Instituto Superior de Agronomia, Tapada da Ajuda 1349-017 Lisboa, Portugal Centro de Cartografia, Instituto de Investigação Científica Tropical, Tv. Conde da Ribeira 9, 1300-142 Lisboa, Portugal. Max Planck Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany The European Space Agency (ESA) World Fire Atlas (WFA), for the period 1997–2002, is built using night time data from the Along Track Scanning Radiometer (ATSR) onboard the Second European Remote-Sensing Satellite (ERS-2). The spatial resolution of the data is 1 km and the satellite revisiting period is 3 days at the equator. The WFA is the first and longest archive of global fire observations and has been used in numerous biomass burning studies. Known limitations of the WFA are the inclusion of warm surfaces, gas flares, and city lights, and an underestimation of actual global fire activity, due to the time of satellite overpass. Nevertheless, it has been considered that the WFA contains a relatively small proportion of observations that do not correspond to vegetation fires. We used ancillary land cover, night-lights and volcanic activity datasets, combined with statistical techniques to detect the occurrence of space-time clusters, to screen the algorithm 2 (308°K threshold) WFA data for the period 1997–2002. During the study period, the annual percentage of false alarms and non-vegetation fires varied from a minimum value of 20.6% in 1997 to a maximum of 27.9% in 1998. Gas flares and hot bare soils are the major sources of false alarms and non-vegetation fires.