Satellite signatures of the Notre Dame Cathedral fire in Paris, France

April 15th, 2019 |

EUMETSAT Meteosat-11 Shortwave Infrared (3.92 µm) images, with airport identifiers plotted in red [click to play animation | MP4]

EUMETSAT Meteosat-11 Shortwave Infrared (3.92 µm) images, with airport identifiers plotted in red [click to play animation | MP4]

The subtle thermal anomaly (or “hot spot”) from the Notre Dame Cathedral Fire was evident in 4.8-km resolution (at satellite nadir) EUMETSAT Meteosat-11 Shortwave Infrared (3.92 µm) imagery (above) as a cluster of brighter yellow pixels just north of Paris Orly International Airport (LFPO) near the center of the images on 15 April 2019.

The fire reportedly began around 1650 UTC; the maximum 3.92 µm brightness temperature sensed by Meteosat-11 was 284.5 K (11.35ºC) on the 1745 UTC image, not long after the fire had spread to the large spire of the cathedral (Meteosat-11 was actually scanning the Paris area at 1756 UTC, since the Meteosat Second Generation satellites scan each Full Disk from south to north). Clouds approaching from the west began to mask the fire signature at 1930 UTC.

Even though high clouds had begun to move overhead, a thermal signature (darker black pixel) could still be seen in 1-km resolution Metop-A and Metop-C Shortwave Infrared (3.75 µm) images at 2009 and 2048 UTC (below, courtesy of William Straka, CIMSS). The maximum 3.75 µm brightness temperature detected by Metop was 291.1 K (18.0ºC).

Metop-A and Metop-C Shortwave Infrared (3.74 µm) images at 2009 and 2048 UTC [click to enlarge]

Metop-A and Metop-C Shortwave Infrared (3.75 µm) images at 2009 and 2048 UTC [click to enlarge]

GOES-17 Loop Heat Pipe Effects on 14 April 2019

April 15th, 2019 |

16-Panel GOES-17 Full-Disk Advanced Baseline Imager (ABI) Imagery, 0010 – 2340 UTC on 14 April 2019 (Click to play mp4 animation)

Solar illumination of the GOES-17 Advanced Baseline Imagery (ABI) was at a maximum on 14 April, so that the effects of the Loop Heat Pipe that is not operating at its designed capacity (and therefore cannot keep the ABI detectors as cold as preferred) were at their worst. (This image of the predicted Focal Plane Temperature from this blog post shows the mid-April peak to be warmest). The animation above shows that only Band 14 (11.2 µm) was able to send a useable signal during the entire night. The Band 14 data are biased, however. The image below compares GOES-16 and GOES-17 temperatures over a region on the Equator (here, from the GOES-17 perspective, and here, from the GOES-16 perspective, from this website) equidistant between the two sub-satellite points (75.2º W for GOES-East, 137.2º W for GOES-West).  GOES-17 slowly cools relative to GOES-16 (assumed to be ‘truth’) before undergoing a series of cold/warm/cold oscillations relative to GOES-16.   So while a useful signal is preserved, algorithms that rely on threshold temperatures, or brightness temperature difference fields (such as the 3.9 µm – 11.2 µm Brightness Temperature Difference), would likely produce unexpected results.

ABI Band 14 (11.2 µm) temperature differences, GOES-17 – GOES-16 on 14 April 2019 (Click to enlarge). Representative Band 14 images during a time largely unaffected by Loop Heat Pipe issues are shown at top.

 

Loop Heat Pipe issues should slowly subside over the coming weeks.  ‘Predictive Calibration’ is likely to be in place by the time the (Northern Hemisphere) Autumnal Equinox arrives.  This will extend the useful signal for the ABI channels.  One might even conclude that this current episode will have the worst impact on useable imagery from the ABI.