Click on the image above to download the associated loop images.
Biomass burning can be monitored using the 3.9 um imagery. In this loop, covering one afternoon and evening, hundreds of fires can be seen as bright spots, covering large regions of northern Brazil. As described in earlier discussions on reflection at 3.9 um, water clouds are white and cirrus clouds are dark in this product; while thin cirrus around the edge of a thunderstorm anvil appear as filmy, slightly brighter regions. Also, in recalling the discussion regarding the difference in response at 3.9 versus 10.7 um for partially filled FOVs (the first "Fire Detection" display page), it can be seen that this product portrays fire areas as regions of enhanced "reflected energy" at 3.9 um, where the increased radiance is solely due to the fire's contribution.
The image above, from 10 September 1995, 1845-2115 UTC, reveals the magnitude of biomass burning. Note that the 3.9 um "reflected product" continues to show the fire areas at night, as would the normal 3.9 um imagery, after the smoke plumes are no longer trackable with VIS imagery.
The "reflected product" is also useful at night for detecting other sub-pixel related phenomena such as cities or a hurricane's eye that is covered by thin cirrus.