Pyrocumulonimbus cloud in South Africa

October 29th, 2018 |

Meteosat-11 Visible (0.8 µm), Shortwave Infrared (3.92 µm) and Longwave Infrared Window (10.8 µm) images [click to play animation | MP4]

Meteosat-11 Visible (0.8 µm, top), Shortwave Infrared (3.92 µm, center) and Longwave Infrared Window (10.8 µm, bottom) images [click to play animation | MP4]

The Garden Route Fires had been burning since about 24 October 2018 near George along the southern coast of South Africa (media story). On 29 October, EUMETSAT Meteosat-11 High Resolution Visible (0.8 µm), Shortwave Infrared (3.92 µm) and Longwave Infrared Window (10.8 µm) images (above) showed an elongated west-to-east oriented thermal anomaly or fire “hot spot” (red pixels) just northeast of George (station identifier FAGG) on Shortwave Infrared imagery during the hours leading up to the formation of a pyrocumulonimbus (pyroCb) cloud around 1300 UTC. The pyroCb exhibited the characteristic warm (+10 to +15ºC, darker gray enhancement) shortwave infrared cloud-top signature just off the coast at 1315 UTC, — this is due to enhanced solar reflection off ice crystals that are smaller compared to those of conventional thunderstorm tops.

Zooming out a bit to follow the southeastward drift of the pyroCb cloud (below), the coldest cloud-top 10.8 µm infrared brightness temperature (BT) was -61ºC (darker red enhancement) at 1315 UTC — then the cloud tops remained in the -55 to -59ºC range (orange enhancement) for the next 6 hours or so. Leveraging the large difference between cold 10.8 µm and warm 3.92 µm BTs, NRL calculates a pyroCb index, which classified this feature as an “intense pyroCb” (1315 UTC | animation). The coldest 10.8 µm cloud-top BT of -61ºC roughly corresponds to an altitude of 13.5 km based on 12 UTC rawinsonde data from Port Elizabeth (plot | list).

Meteosat-11 Shortwave Infrared (3.92 µm, left) and Longwave Infrared Window (10.8 µm, right) images [click to play animation | MP4]

Meteosat-11 Shortwave Infrared (3.92 µm, left) and Longwave Infrared Window (10.8 µm, right) images [click to play animation | MP4]

Imagery from NOAA-19 at 1420 UTC (courtesy of René Servranckx) also revealed the warm (dark gray) Shortwave Infrared pyroCb signature, along with a minimum cloud-top infrared BT of -58.1ºC (below).

NOAA-19 AVHRR imagery at 1420 UTC [click to enlarge]

NOAA-19 AVHRR imagery at 1420 UTC [click to enlarge]

A Suomi NPP VIIRS True Color Red-Green-Blue (RGB) image at 1230 UTC (below) was about a half hour before the formation of the pyroCb, but it did show a signature of smoke drifting southeastward off the coast.

Suomi NPP VIIRS True Color RGB image [click to enlarge]

Suomi NPP VIIRS True Color RGB image [click to enlarge]

On the following day (30 October), a NOAA-20 VIIRS True Color image (below) showed the classic comma cloud signature of a mid-latitude cyclone south of the coast, with the band of cold-frontal clouds extending northward across Lesotho. Note the thick plume of smoke spreading eastward within the strong post-frontal westerly winds.

NOAA-20 VIIRS True Color RGB image [click to enlarge]

NOAA-20 VIIRS True Color RGB image [click to enlarge]

A time series of of surface observations from George (below) supported the idea of a cold frontal passage: ahead of the front, temperatures rapidly rose to 104ºF/40ºC (with a dew point of 39ºF/4ºC) on 28 October about 1.5 hours prior to the formation of the pyroCb — then strong westerly winds (gusting to 40 knots/21 mps) with rising pressures and falling temperatures followed on 30 October.

Time series plot of of surface observations from George [click to enlarge]

Time series plot of of surface observations from George [click to enlarge]

The pyroCb research community believes that this is the first documented case of a pyroCb on the African continent.

 

Delta Fire pyroCumulonimbus cloud in California

September 5th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), “Clean” Infrared Window (10.3 µm, bottom left) and Cloud Top Temperature product (bottom right) [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and Cloud Top Temperature product images displayed using AWIPS (above) showed the formation of a pyroCumulonimbus (pyroCb) cloud generated by the Delta Fire in Northern California late in the day on 05 September 2018. As the pyroCb cloud drifted eastward toward the California/Nevada border, Cloud Top Temperature values cooled to a minimum of -53ºC (lighter green enhancement) at 0300 UTC. Note the pulsing behavior of updrafts over the fire area: 2 distinct updraft pulses were apparent (at 0022 UTC and 0042 UTC), with the later pulse producing the pyroCb.



A longer animation of GOES-16 “Red” Visible, Shortwave Infrared and “Clean” Infrared Window images displayed using McIDAS (below) showed that the first hot (red) Shortwave Infrared pixels appeared at 2027 UTC. The fire caused a 5-mile section of Interstate 5 to be closed.

GOES-16 "Red" Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle), "Clean" Infrared Window (10.3 µm, bottom); Interstate 5 is plotted in cyan [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.3 µm, bottom) images; Interstate 5 is plotted in cyan [click to play animation | MP4]

GOES-17 (positioned at 89.5º W longitude during its post-launch checkout phase) had a more direct view of the pyroCb than GOES-16 (positioned over the Atlantic Ocean at 75.2º W longitude) — and GOES-17 “Red” Visible, Shortwave Infrared and “Clean” Infrared Window images are shown below. Unfortunately the default GOES-17 Western US Mesoscale Domain Sector was shifted farther to the south on this day, so 1-minute imagery of the pyroCb event was not available.

GOES-17 "Red" Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle), "Clean" Infrared Window (10.3 µm, bottom) images; Interstate 5 is plotted in cyan [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.3 µm, bottom) images; Interstate 5 is plotted in cyan [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

A Nebraska thunderstorm and a Wyoming wildfire, as viewed by GOES-15, GOES-17 and GOES-16

August 29th, 2018 |
Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right), with SPC storm reports plotted in red [click to play animation | MP4]

Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right), with SPC storm reports plotted in red [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

A comparison of Visible images from GOES-15 (GOES-West), GOES-17 and GOES-16 (GOES-East) (above) showed an isolated thunderstorm that developed in the Nebraska Panhandle late in the day on 29 August 2018. The storm produced hail (SPC storm reports), and also exhibited an Above Anvil Cirrus Plume. The images are displayed in the native projection of each satellite, with no re-mapping.

One other feature that was seen north of the thunderstorm was smoke which was being transported eastward from the Britania Mountain Fire in southeastern Wyoming. The smoke was more apparent on the GOES-17 and GOES-16 images as forward scattering increased toward sunset.

Shortwave Infrared imagery from the 3 satellites revealed important differences affecting fire detection: namely spatial resolution and viewing angle. The 3.9 µm detector on the GOES-15 Imager has a spatial resolution of 4 km (at satellite sub-point), compared to 2 km for the GOES-16/17 ABI. Given that the fire was burning in rugged mountain terrain, the view angle from each satellite had an impact on the resulting bire brightness temperature values. For example, the first indication of very hot (red-enhanced) pixels was at 1527 UTC from GOES-16/17, vs 1715 UTC from GOES-15; at the end of the day, the very hot fire pixels were no longer seen with GOES-15 after 2300 UTC, but continued to show up in GOES-17 imagery until 0042 UTC and in GOES-16 imagery until 0122 UTC.

Shortwave Infrared images from GOES-15 (3.9 µm, left), GOES-17 (3.9 µm, center) and GOES-16 (3.9 µm, right) [click to play animation | MP4]

Shortwave Infrared images from GOES-15 (3.9 µm, left), GOES-17 (3.9 µm, center) and GOES-16 (3.9 µm, right) [click to play animation | MP4]

Wildfires in British Columbia

August 17th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and Shortwave Infrared (3.9 µm, right) images [click to play MP4 animation]

A 2-panel comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed the smoke plumes and thermal anomalies or “hot spots” (darker black to red pixels) associated with a flare-up of wildfires in western British Columbia on 17 August 2018.

A sequence of Shortwave Infrared (3.7 µm) images from Terra / Aqua MODIS and Suomi NPP / NOAA-20 VIIRS (below) revealed the diurnal changes in areal coverage and intensity of the thermal signature of the fires.

Shortwave Infrared (3.7 µm) images from Terra / Aqua MODIS and Suomi NPP / NOAA-20 VIIRS [click to enlarge]

Shortwave Infrared (3.7 µm) images from Terra / Aqua MODIS and Suomi NPP / NOAA-20 VIIRS [click to enlarge]

Toggles between Visible and Shortwave Infrared images from Terra MODIS (1912 UTC), NOAA-20 VIIRS (1950 UTC) ans Suomi NPP VIIRS (2129 UTC) are shown below (note: the NOAA-20 images are incorrectly labeled as Suomi NPP). It is interesting to note the impact that the smoke plume had on the air temperature at Quesnel (CYQZ) — because the smoke layer was optically dense enough (VIIRS True Color image) to significantly reduce incoming solar radiation, the temperature was as much as 14-18ºF (8-10ºC) cooler than Prince George (CYXS) to the north and Williams Lake (CYWL) to the south.

Terra MODIS Visible (0.65 µm) and Shortwave Infrared (3.7 µm) images [click to enlarge]

Terra MODIS Visible (0.65 µm) and Shortwave Infrared (3.7 µm) images at 1912 UTC [click to enlarge]

NOAA-20 VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images [click to enlarge]

NOAA-20 VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images at 1950 UTC [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images at 2129 UTC [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images at 2129 UTC [click to enlarge]

Farther to the east in Alberta, thick smoke caused very poor air quality in cities like Edmonton and Grande Prairie (photo 1 | photo 2). Daily composites of Suomi NPP VIIRS True Color RGB images from 11 August to 17 August (below) revealed the transport of smoke across British Columbia, Alberta and Saskatchewan.

Daily composites of Suomi NPP VIIRS True Color RGB images (with VIIRS fire detections in red), 11-17 August [click to play MP4 | Animated GIF]

Daily composites of Suomi NPP VIIRS True Color RGB images (with VIIRS fire detections in red), 11-17 August [click to play MP4 | Animated GIF]

A time series of surface reports from Edmonton, Alberta covering the period 14-17 August (below) showed that smoke restricted the surface visibility there to 1.5 miles on 15 August and 17 August.

Time series of surface reports from Edmonton, Alberta during the period 14-17 August [click to enlarge]

Time series of surface reports from Edmonton, Alberta during the period 14-17 August [click to enlarge]

===== 19 August Update =====

* GOES-17 images shown here are preliminary and non-operational *

GOES-17 Near-Infrared

GOES-17 Near-Infrared “Cloud Particle Size” (2.24 µm, left) and Shortwave Infrared (3.9 µm, right) images [click to play 81 Mbyte MP4 animation]

A 2-panel comparison of GOES-17 Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images during the 7-day period of 13-19 August (above) showed the diurnal changes in thermal signatures of the ongoing British Columbia wildfires. The nighttime thermal signatures seen on the 2.24 µm images (brighter white pixels) result from the fact that this spectral band is located close to the peak emitted radiance of very hot features such as active volcanoes or large fires (below).

Plots of Spectral Response Functions for ABI Bands 5, 6 and 7 [click to enlarge]

Plots of Spectral Response Functions for ABI Bands 5, 6 and 7 [click to enlarge]