Two PyroCbs in Alaska

On 15 July two pyroCbs formed in the interior of Alaska. GOES-15 detected the smoke plumes and pyroCb clouds, as well as the fire hot spots. The first pyroCb (65.8º N, 155.5º W) formed from the Dulbi Flats fire around 1:30 UTC . The second pyroCb (66.6º N, 153.8ºW ) formed from the Hog Fire, also around 1:30 UTC.  Starting at 21:00 UTC on 14 July, the animation below (also available as an MP4) )shows GOES-15 (GOES-West) 0.63 µm visible (top), 3.9 µm shortwave IR (middle) and 10.7 µm IR window images (bottom). In the shortwave IR images, the red pixels indicate very hot IR brightness temperatures exhibited by the fire source regions.

GOES-15 0.63 µm visible (top), 3.9 µ shortwave IR (middle) and IR window (10.7 µm) images [click to play animation]

GOES-15 0.63 µm visible (top), 3.9 µ shortwave IR (middle) and IR window (10.7 µm) images [click to play animation]

A 1-km resolution NOAA-18 image at 03:07 UTC (below; courtesy of René Servranckx) showed the cloud-top IR brightness temperature for the first pyroCb to be -50.2º C (yellow color enhancement) and the second pyroCb to be -48.3º C (dark green color enhancement).

NOAA-18 AVHRR 0.64 µm visible (top left), 3,7 µm shortwave IR (top right), 10.8 µm IR window (bottom left) and false-color RGB composite image (bottom right). [click to enlarge]

NOAA-18 AVHRR 0.64 µm visible (top left), 3,7 µm shortwave IR (top right), 10.8 µm IR window (bottom left) and false-color RGB composite image (bottom right). [click to enlarge]

On the following morning, a Suomi NPP VIIRS Day/Night Band (0.7 μm) image (below) provided a good view of the smoke plume, which had drifted eastward as far as the Alaska/Yukon border. Numerous fire hot spots were still seen on the corresponding VIIRS shortwave IR (3.74 μm) image (yellow to red color enhancement); note how there was no signature of the smoke plume on the VIIRS IR Window (11.45 μm) image, since smoke is transparent to thermal radiation at that wavelength.

Suomi NPP VIIRS Day/Night Band (0.7 μm), Shortwave Infrared (3.74 μm) and Infrared Window (11.45 μm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 μm), Shortwave Infrared (3.74 μm) and Infrared Window (11.45 μm) images [click to enlarge]

Later in the day, Suomi NPP OMPS Aerosol Index (AI) values within the smoke plume feature (below; OMPS data courtesy of Colin Seftor) were as high as 8.0 (67.35ºN, 140.52ºW at 21:01:42 UTC) and 6.0 (66.96º N, 139.16º W at 22:42:33 UTC).

Suomi NPP OMPS Aerosol Index [click to enlarge]

Suomi NPP OMPS Aerosol Index [click to enlarge]

An overpass of the CALIPSO satellite after 13 UTC provided CALIOP data showing a portion of the smoke plume aloft, which exhibited high values of attenuated backscatter and low values of depolarization ratio (below).

CALIPSO CALOIP attenuated backscatter and depolarization data; Alaska pyroCb smoke plume aloft indicated by arrow [click to enlarge]

CALIPSO CALOIP attenuated backscatter and depolarization data; Alaska pyroCb smoke plume aloft indicated by arrow [click to enlarge]

===== 16 July Update =====

Suomi NPP OMPS Aerosol Index images from 16 July (below) showed that smoke from the Alaska pyroCbs continued to drift eastward across the Yukon and Northwest Territories regions of Canada.

Suomi NPP OMPS Aerosol Index images [click to enlarge]

Suomi NPP OMPS Aerosol Index images [click to enlarge]

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