The Tunnel Fire north of Flagstaff offers an excellent example of why knowledge of Parallax with satellite features is important. In the animations above, note how the location of the warmest pixels are shifted: GOES-17 has the warmest pixels very close to US Highway 89 leading northeast away from Flagstaff; GOES-16 has the warmest pixels just to the west of that road! Which is correct?

Even with surface-based features such as fires, parallax (see other blog posts dealing with parallax here, here, here and here) is an issue with GOES imagery. (Click here to see parallax with lakes) The perceived location is shifted away from the sub-satellite point. So for this example, the true fire location might be somewhere between the satellite-indicated locations. Note also that the FDCA values from GOES-17 differ from those GOES-16; for this fire, GOES-17 values were warmer.

NOAA-20 overflew this fire at 20:50, 20:30 and 20:10 on 19, 20 and 21 April, and imagery from the NASA Worldview site is shown below (Click here for a direct link to the 20 April scene) VIIRS imagery typically has smaller parallax shifts than GOES (and in fact, as detailed here, considerable effort has gone into better georeferencing of VIIRS imagery, as discussed in this blog post and shown in this toggle), and the fire location is therefore more accurate. The 20 April view from NOAA-20 occurred shortly after the end of the animation above, and shows a fire straddling the highway.

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A toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 0954 UTC or 3:54 am local time (above) displayed the nighttime glow and thermal signatures of actively-burning portions of the Tunnel Fire on 20 April 2022. As noted in the Inciweb report, a 10-mile section of the north-south U.S. Highway 89 was closed (from milepost 425 to 435) as the fire crossed that road.

After sunrise, GOES-17 (GOES-West) Fire Temperature RGB, Shortwave Infrared (3.9 µm), Fire Power and Fire Temperature images (below) showed how the fire intensified during the day (the Fire Temperature and Fire Power derived products are components of the GOES Fire Detection and Characterization Algorithm FDCA).

A longer animation of GOES-17 Fire Temperature RGB images created using Geo2Grid is shown below. The less-intense signature of the Crooks Fire is also apparent, to the southwest of the more prominent Tunnel Fire.

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JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed signatures of a rapidly-spreading grassland fire in eastern Mongolia’s Numrug National Park (near the border with China) on 19 April 2022. The fast rate of northeastward growth of the dark burn scar in Visible imagery was particularly striking. Strong winds aided the rapid expansion of this fire, due to the tight pressure gradient between a high over central China and a deepening low that was moving from Siberia to northeastern China (surface analyses).

Consecutive NOAA-20 VIIRS Infrared image valid at 0401 UTC and 0541 UTC — viewed using RealEarth (below) — showed the eastward drift of individual small pyrocumulonimbus (pyroCb) clouds, which exhibited cloud-top infrared brightness temperatures of -40ºC and colder (brighter green color enhancement).

A toggle between NOAA-20 VIIRS True Color RGB and Infrared images at 0541 UTC (below) depicted the dark burn scar as well as the smoke plume with embedded pyroCb clouds.

30-meter resolution Landsat-8 False Color RGB imagery valid at 0252 UTC (below) provided an even more detailed view of the dark burn scar — in addition, the active fire front appeared as brighter shades of pink to red along the eastern and southeastern flanks.

After sunset, the northern flank of the fire continued to burn at an intense rate, judging from the thermal signature seen in Himawari-8 Shortwave Infrared images (below). Dense layered clouds began to move over the region before sunrise the next day, which then acted to mask the fire’s thermal signature.

A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images valid at 1757 UTC (below) showed the bright nighttime glow of active fires — especially along the aforementioned northern flank — in addition to the associated smoke plume that was moving eastward, as illuminated by the Moon (which was in the Waning Gibbous phase, at 90% of Full). This smoke did not exhibit a signature in the corresponding 11.45 µm Infrared image, since relatively thin smoke layers are generally transparent to upwelling surface radiation at longer wavelengths.

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At 1500 UTC today, the Set Point temperature on the cryocooler was re-set to a cooler temperature (the effect of the warmer Set Point temperature is discussed here: Bands 10 and 12 had more lines of missing data related to the warming of the satellite by the Sun). The cryocooler works to reduce the thermal load on the satellite, but during seasonal peak heating (see the figure on Page 5 in this document), it is unable to counteract fully the effects of the malfunctioning Loop Heat Pipe on GOES-17.

The figure below compares Focal Plane Temperatures on 16 April (with the warmer Set Point temperature) and 19 April (during which day the cooler Set Point Temperature was re-implemented). (More comparison imagery is at this website; imagery for Band 10 on 16 April is here; from 19 April is here) Note how the brightness temperature difference between GOES-16 and GOES-17 is very different (one might say noisy) on 16 April, and on 19 April until about 1530 UTC, after which point it stabilizes at less than about 0.25K warmer for GOES-17. The change in the Focal Plane Module (FPM) Temperature is also apparent: The FPM is about 3K cooler than on 16 April starting around 1500 UTC on 19 April. This is because of the change in the Set Point on the cryocooler that occurred at that time.

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