5-minute GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Fire Temperature RGB images (above) revealed that the Dixie Fire in northern California produced a pair of pyrocumulonimbus (pyroCb) clouds— denoted by cloud-top 10.35 µm infrared brightness temperatures of -40ºC or colder (shades of blue pixels) — late in the day on 19 July 2021. The maximum surface 3.9 µm brightness temperature sensed with this fire was 138.7ºC — which is the saturation temperature for the ABI Band 7 detectors.

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Fire Temperature RGB images (above) revealed that the Bootleg Fire in far southern Oregon produced a pyrocumulonimbus (pyroCb) cloud — denoted by cloud-top 10.35 µm infrared brightness temperatures of -40ºC and colder (darker blue pixels) — late in the day on 14 July 2021. The maximum surface 3.9 µm brightness temperature sensed with this fire was 138.7ºC — which is the saturation temperature for the ABI Band 7 detectors.

A plot of 00 UTC rawinsonde data from nearby Medford, Oregon (below) indicated that the -40ºC temperature closely corresponded to the height of the tropopause and the Most Unstable (MU) air parcel Equilibrium Level (EL).

On the following morning, signatures of the upper-tropospheric/lower-stratospheric smoke that was forced aloft by the pyroCb cloud could be seen arcing east-southeastward over parts of Idaho, Montana and Wyoming on GOES-17 Visible and Near-Infrared “Cirrus” (1.37 µm) images (below). The smoke signature in 1.37 µm images was not due to the plume being composed of ice particles; rather, the Cirrus imagery is also able to highlight the presence of particles that are highly effective at scattering sunlight (which includes ice crystals, dust, volcanic ash, smoke) — and the smoke signature was also further highlighted by a favorable forward scattering angle.