In the last ten days of April 2004, at the end of the dry season, MSG observed an increase of fire activity over West Africa.
24 May 2022
27 April 2004
The fires can be observed very well in channel 04 (IR3.9) of MSG SEVIRI, but also in the brightness temperature difference between channel 04 and channel 09 and in RGB composites that make use of channel 04. The fires do not need to cover a full pixel of MSG SEVIRI to be seen, but can already be observed if they cover only a few percent of a pixel.
For instance, in Africa, a hot fire (ca. 500K) of about 500 x 500m increases the brightness temperature of channel 04 by about 2 K. MODIS (on Terra and Acqua), with a maximum horizontal resolution of 250m, can detect fires of sizes down to about 50 x 50m.