Heat signatures from the fire that destroyed part of the historic Parisian cathedral Notre-Dame in April 2019 could be seen on satellite imagery.
By William Straka III (CIMSS), Ivan Smiljanic (SCISYS)
On 15 April, just before 16:20 UTC (18:20 CEST), a fire broke out beneath the roof of Notre-Dame Cathedral, Paris.
While there were clouds present in the region the fire could be seen with the SEVIRI instrument on Meteosat-11, using Band 4 or 3.9 µm channel (Figure 2), which is often used for nighttime fire detection. Higher temperatures appear as darker pixels on the imagery.
The fire was reportedly so intense it melted parts of the roof's lead cladding, which is probably why the high temperature signature was picked up by SEVIRI, even through the clouds.
Figure 2: Meteosat-11 infrared animation, 15 April 16:00–23:15 UTC
Around four hours later at 20:09 UTC, while the fire was still ongoing, Metop-A passed overhead, closely followed at 20:48 UTC by Metop-C, both observing the region around Paris at near-nadir viewing angle (Figure 3).
Although the fire was dying down it could still be easily be seen through a break in the clouds. The 1 km Full Resolution Area Coverage data showed a 3.7 µm brightness temperature of roughly 291.1 K (18.0º C). This temperature is similar to hot spots observed from small wildfires. Even though the cloud had returned by the time Metop-C passed overhead, the hot spot could still be easily seen.
The fire occurred four hours after the Suomi-NPP and NOAA-20 afternoon overpasses, and had been virtually extinguished by the nighttime overpasses. However, this case is a perfect example of how information provided by both European and American satellites and sensors can be used together to monitor the environment and make observations of the impact from both man-made and natural disasters during different times of the day.
Looking at fast-looping imagery over Paris area (Figure 4), one can notice that there are more than one fire-excited pixels (annotated by red rectangle). This is mostly due to transformation/remapping of the sensed information from detector level to a regular pixel grid, as part of the data processing. That way the ‘heat information’ is partially transferred to surrounding pixels.
Figure 4: Meteosat-11 infrared animation, 15 April 15:00–20:00 UTC (looped three times)
Satellite signatures of the Notre Dame Cathedral fire in Paris, France (CIMSS Blog)
Notre Dame Fire Damage Spotted from Space (Photo) (Space.com)
Notre-Dame: Massive fire ravages Paris cathedral (BBC News)
Why the Notre Dame fire was so destructive, according to fire experts (Vox)
The hot, dangerous physics of fighting the Notre Dame fire (Wired)