Pyrocumulonimbus cloud over northern Paraguay

September 29th, 2021 |

GOES-16 Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, center) and Infrared Window (10.35 µm, bottom) images [click to play animation | MP4]

Fires burning in far northern Paraguay on 29 September 2021 created a pyrocumulonimbus or pyroCb cloud — GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the pyroCB cloud, fire thermal anomalies or “hot spots” (clusters of red pixels) and cold cloud-top infrared brightness temperatures, respectively. The minimum 10.35 µm temperature was -47.6ºC at 1840 UTC. Note the relatively warm (darker gray) appearance of the pyroCb cloud in the 3.9 µm images — this is a characteristic signature of pyroCb cloud tops, driven by the smoke-induced shift toward smaller ice particles (which act as more efficient reflectors of incoming solar radiation).

A Suomi-NPP VIIRS Infrared Window (11.45 µm) image at 1751 UTC as viewed using RealEarth (below) revealed cloud-top infrared brightness temperatures in the -60s C (shades of red). Surface temperatures at nearby sites had reached 38ºC (100ºF) by 18 UTC. 

Suomi-NPP VIIRS Infrared Window (11.45 µm) image at 1751 UTC [click to enlarge]

South American pyrocumulonimbus clouds are fairly uncommon — since the first documented case in 2018, only 7 other pyroCbs have been identified over that continent. 

Thanks to Mike Fromm, NRL, for alerting us to this latest pyroCb case. Additional information is available from Metsul.com.

Pyrocumulonimbus clouds produced by the Cougar Peak Fire in Oregon

September 9th, 2021 |

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), “Clean” Infrared Window (10.35 µm, bottom left), and Fire Temperature RGB (bottom right) [click to play animation | MP4]

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 Cougar Peak Fire in southern Oregon produced a pair of pyrocumulonimbus (pyroCb) clouds— denoted by cloud-top 10.35 µm infrared brightness temperatures of -40ºC or colder (with the coldest being -64.9ºC at 0047 UTC) — late in the day on 09 September 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. Since it was exhibiting extreme fire behavior during this time, evacuation orders were being increased for the immediate area.
 
5-minute GOES-17 True Color RGB images created using Geo2Grid (below) showed a larger-scale view of the 2 pyroCb clouds. Also apparent were smoke-filled clouds — characterized by shades of tan to light brown — from fires in northern California, which were drifting north-northeastward across southern Oregon and the Cougar Peak Fire.
 

GOES-17 True Color RGB images [click to play animation | MP4]

Caldor Fire approaches South Lake Tahoe

August 31st, 2021 |
Suomi NPP and NOAA-20 (as indicated) VIIRS Day Night Band visible (0.7 µm) imagery, 11-31 August 2021 (Click to enlarge). Sacramento CA is at the western edge of the imagery, and Reno NV is along the northern boundary.

Day Night Band imagery collected from the VIIRS-Today website, above, shows night-time snapshots of the Caldor Fire (discussed previously here, here and here on this blog) as it formed and moved towards Lake Tahoe in August 2021. On 31 August, the last day of the animation, the fire was close enough to the city of South Lake Tahoe that evacuation orders for that town have been issued.

The longer animation, below, shows the evolution of the Caldor Fire and the Dixie Fire complex as well (and is an update to this blog post).

Suomi NPP and NOAA-20 (as indicated) Day Night Band Imagery, 9 July – 31 August 2021 (Click to enlarge)

VIIRS imagery can also be used to outline burn scars from the fire. The ‘False Color’ RGB image below, from 30 August 2021 (from this url at VIIRS Today), depicts just how large the burn scar (the brownish region in the imagery) from the Dixie Fire is.

NOAA-20 False Color imagery from 30 August 2021 (Click to enlarge)

Smoke plumes continue from Northern California wildfires

August 30th, 2021 |

GOES-17 True Color RGB images [click image to play animation | MP4]

GOES-17 (GOES-West) True Color RGB images created using Geo2Grid (above) showed the diurnal variation of smoke from the Dixie Fire and the Calfor Fire in Northern California on 30 August 2021. Early in the day, smoke from the previous day of fire activity that had settled into valleys was apparent — however, as daytime heating continued this valley smoke was ventilated and mixed to higher altitudes, with new smoke plumes eventually developing as the fire activity ramped up once again. Occasional brighter-white pyrocumulus clouds were produced over the hottest portion of the larger fires.

===== 31 August Update =====

GOES-17 True Color RGB images [click image to play animation | MP4]

GOES-17 (GOES-West) True Color RGB images created using Geo2Grid (above) showed the diurnal variation of smoke from the Dixie Fire, Caldor Fire and Tamarack Fire in Northern California on 31 August 2021. Early in the day, smoke from the previous day of fire activity that had settled into valleys was evident — but as daytime heating continued, this valley smoke was ventilated and mixed to higher altitudes, with new smoke plumes eventually developing as the fire activity ramped up once again. Occasional brighter-white pyrocumulus clouds were produced by the larger, hotter fires.

In a toggle between Suomi NPP VIIRS True Color RGB and False Color RGB images (below), recent fire burn scars appear as darker shades of reddish-brown while currently active and hot fires appear as brighter shades of pink in the False Color image. 

Suomi NPP VIIRS True Color RGB and False Color RGB images [click to enlarge]

Suomi NPP VIIRS False Color RGB images 5 days apart — 26 August and 31 August — (below) revealed changes in fire burn scar size and active fire locations across that region.

Suomi NPP VIIRS False Color RGB images on 26 August and 31 August [click to enlarge]

A closer view of Suomi NPP VIIRS True Color RGB and False Color RGB mages centered on the Caldor Fire (below) showed that a large active fire was located just a few miles south of South Lake Tahoe, California. 

Suomi NPP VIIRS True Color RGB and False Color .RGB images [click to enlarge]