PyroCb

Two Bulls Fire near Bend, Oregon

Scott Bachmeier | June 8, 2014

GOES-15 0.63 µm visible channel (left) and 3.9 µm shortwave IR channel (right) images (click to play animation)

On 07 June 2014, McIDAS images of 1-km resolution GOES-15 0.63 µm visible channel and 3.9 µm shortwave IR channel images (above; click image to play animation) showed that the Two Bulls Fire just west of Bend, Oregon (station identifier KBDN) began to burn an area large enough to be detected by satellite around 20:00 UTC (1:00 PM local time), when a shortwave IR brightness temperature of 314.9 K was seen. Within 15 short minutes, the fire “hot spot” exhibited a shortwave IR brightness temperature of 339.6 K — the saturation temperature for the GOES-15 3.9 µm detectors — which continued for another 5.5 hours until 01:41 UTC on 08 June.

The corresponding 4-km resolution GOES-15 10.7 µm longwave IR channel images (below; click image to play animation) offered a hint that there may have been a brief pyrocumulonimbus (pyroCb) cloud at 00:30 UTC on 08 June, when a single pixel exhibited an IR brightness temperature value of -30º C (dark blue color enhancement). However, the GOES-15 satellite was in Full Disk scan mode during the time of formation of this potential pyroCb cloud, so images were only available every 30 minutes during this critical period.

GOES-15 10.7 µm IR channel images (click to play animation)

Luckily, an overpass of the NOAA-16 polar-orbiting (or POES) satellite offered an excellent 1-km resolution view with the AVHRR 12.0 µm IR channel — a minimum IR brightness temperature of -49.0º C (yellow color enhancement) was detected at 00:32 UTC (below). Other POES AVHRR images can be seen here (courtesy of Rene Servranckx).

POES AVHRR 12.0 µm IR image

The Two Bulls Fire continued to burn into the following night, and a comparison of 375-meter resolution Suomi NPP VIIRS 3.74 µm shortwave IR and 750-meter resolution VIIRS 0.7 µm Day/Night Band images at 09:28 UTC (2:28 AM local time) showed a distinct fire “hot spot” on the shortwave IR, with the DNB image revealing the bright glow of the large fire just west of the glow of the city lights of Bend, Oregon (below). The Bend Municipal Airport is located well to the northeast of the city of Bend, explaining the offset of the city lights and the airport observation.

Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

A comparison of the 375-meter resolution Suomi NPP VIIRS 3.74 µm with a 4-km resolution GOES-15 3.9 µm shortwave IR images around 09:30 UTC (below) demonstrated the clear advantage of improved spatial resolution for the detection of fire hot spot: VIIRS gave a maximum shortwave IR brightness temperature of 52.5º C, compared to only 14.5º C on the GOES-15 image.

Suomi NPP VIIRS 3.74 µm and GOES-15 3.9 µm shortwave IR images

On the following morning of 08 June, GOES-15 0.63 µm visible channel images (below; click image to play animation) showed that large amounts of smoke had been transported southward over northern California, and especially southeastward over Nevada. Later in the day on 08 June, pilot reports over northern California indicated that the top of the smoke layer was at an altitude of 11,000 feet.

GOES-15 0.63 µm visible channel images (click to play animation)

PyroCb in the Irkutsk region of Siberia

Scott Bachmeier | May 18, 2014

COMS-1 0.675 µm visible channel images (click to play animation)

The first unambiguous pyroCb event of the 2014 Northern Hemisphere wildfire season occurred in the Irkutsk region of Siberia, Russia on 18 May 2014. Korean COMS-1 satellite 0.675 µm visible channel images (above; click image to play animation; also available as an MP4 movie file) showed an increasing amount of smoke output from numerous fires burning northwest of Lake Baikal; toward the end of the day, a strong cold front moving eastward across the region appeared to be the catalyst for producing a pair of pyroCb events in the vicinity of Bratsk (station identifier UIBB).

A time series of surface weather for Bratsk (below) showed that smoke had been reducing surface visibility to 3-4 miles during the overnight and early morning hours, but the visibility then dropped to 1.9 miles as south-southeasterly winds began to increase ahead of the arrival of the cold front. Once the cold front passed, the surface air temperature dropped from 73ºF (22.8ºC) at 08 UTC to 43ºF (6.1ºC) at 13 UTC, as westerly winds gusted as high as 33 knots.

Bratsk (UIBB) time series of surface data

The corresponding COMS-1 10.8 µm IR channel images (below; click image to play animation; also available as an MP4 movie file) indicated that for the second, more explosive pyroCb northeast of Bratsk the cloud-top IR brightness temperature crossed the -40ºC threshold at 10:45 UTC, and then became colder than -50ºC at 11:00 UTC (IR/visible image comparison). The coldest cloud-top IR brightness temperature was -57.8 at 13:15 UTC.

COMS-1 10.8 µm IR channel images (click to play animation)

Looking at the 12 UTC rawinsonde data from Bratsk (below), the -57.8ºC cloud-top IR brightness temperature roughly corresponded to an altitude of 10.2-10.7 km.

Bratsk rawinsonde data ( 12 UTC on 18 May 2014)

Multi-angle Imaging SpectroRadiometer (MISR) smoke plume heights (below) confirmed that the maximum height of the smoke plume was in the 11-12 km range.

Multi-angle Imaging SpectroRadiometer (MISR) smoke plume heights

Using the NOAA ARL HYSPLIT model, forward airmass trajectories originating at the 2 pyroCb initiation sites near Bratsk (below) suggested an anticyclonic transport aloft over far northeastern Russia, eventually crossing over the Sea of Okhotsk.

NOAA ARL HYSPLIT forward airmass trajectories

The anticyclonic transport of smoke was confirmed by images of Suomi NPP OMPS Aerosol Index on 19 and 20 May (below; courtesy of Colin Seftor).

Suomi NPP OMPS Aerosol Index

A similar anticyclonically-curved signal of smoke aloft was seen on the AIRS Carbon Monoxide mixing ratio product from 18 May (below).

AIRS Carbon Monoxide mixing ratio

Fires in eastern Russia and Mongolia

Scott Bachmeier | March 29, 2014

MTSAT-2 0.68 µm visible channel (left) and 3.75 µm shortwave IR channel (right) images (click to play animation)

MTSAT-2 0.68 µm visible channel and 3.75 µm shortwave IR channel images (above; click image to play animation) showed that numerous wildfires had developed over far southeastern Russia (near the Russia/Mongolia/China border) during the day on 29 March 2014. A portion of Lake Baikal is outlined in blue in the far upper left corner of the images; the largest of the still-frozen lakes seen in the lower center portion of the images was Hulun Lake in far northeastern China. The only regularly-reporting surface station in the area was Chita, Russia (station identifier UIAA) – note the sharp drop in dew point temperatures during the day, falling from +18º F (-7.8º C) at 22 UTC on 27 March to -4º F (-20.0º C) at 05 UTC on 28 March. This sharp drop in dew point was accompanied by westerly to northwesterly winds with sustained speeds of 20 knots (10.3 meters per second).

The corresponding MTSAT-2 10.8 µm IR channel images (below; click image to play animation) revealed that the large cluster of fires southeast of Chita generated a pyroCumulonimbus (pyroCb) cloud shortly before 09:32 UTC; the minimum IR brightness temperature of this pyroCb cloud was -46.6º C (lighter yellow color enhancement) at 10:32 UTC. However, the pyroCb cloud top IR brightness temperatures then began to rapidly warm after 11:32 UTC.

MTSAT-2 10.8 µm IR channel images (click to play animation)

Large bushfires in southeastern Australia

Scott Bachmeier | January 16, 2014

MTSAT-2 0.68 µm visible channel (left) and 3.75 µm shortwave IR (right) images (click to play animation)

An extended period of hot, dry weather led to the development of multiple large bushfires across parts of southeastern Australia, some of which began to produce pyrocumulonimbus (pyroCb) clouds during the 15-16 January 2014 period. McIDAS images of MTSAT-2 0.68 µm visible channel and 3.75 µm shortwave IR channel data (above; click image to play animation; also available as an MP4 animation) showed the development of a well-defined pyroCb associated with the Northern Grampions fire in the state of Victoria. After the visible images on the left panels faded to black during the night-time hours, the shortwave IR images on the right panels showed that many of the fire “hot spots” (denoted by the darker black pixels) continued to grow during the night.

MTSAT-2 10.8 µm longwave IR channel images (below; click image to play animation; also available as an MP4 animation) indicated that cloud-top IR brightness temperatures associated with the rapidly-growing pyroCb cloud became as cold as -38.7º C (lighter green color enhancement) at 07:32 UTC. Other areas of cold-topped thunderstorms developed near the coast, likely initiated by sea breeze and/or local terrain influences. Surface reports ploted on the IR images revealed very hot temperatures: for example, it was 109º F (42.8º C) at Melbourne Essondon (station identifier YMEN) at 04 UTC.

MTSAT-2 10.8 µm longwave IR images (click to play animation)

A larger-scale view of MTSAT-2 0.68 µm visible channel images (below, visualized using the SSEC RealEarth web map server) showed that there were also some large bushfires to the northwest that were producing long, dense smoke plumes which were drifting southward off the coast.

MTSAT-2 0.68 µm visible channel images (click to play animation)

Bush fires in the Sydney, Australia region

Scott Bachmeier | October 17, 2013

Update 10/21/13:

While there’s still no clear indication of pyroconvection from the MTSAT imagery, the Sydney fires have continued to burn over the weekend, belching large quantities of smoke over the western Pacific. The MTSAT-2 visible and shortwave infrared loop (below; click image to play animation) contains hourly images from 00:32UTC on Oct. 17 to 16:32UTC on Oct. 21. While the temporal resolution of the MTSAT-2 imagery over this region is somewhat coarse (hourly images instead of 30 or 15 minute images), it is still possible to see the time evolution of these fires (dark black pixels) in the infrared imagery and their smoke emission in the visible imagery. While it is possible that some brief pyroconvection may have been missed due to the lack of imagery, it is unlikely that a full pyrocumulonimbus formed and decayed entirely in an hour.

MTSAT-2 visible channel (left) and shortwave IR channel (right) images (click to play animation)

The Aqua MODIS 250m true color imagery from Oct. 21 offers a better view of the sizable smoke plumes being created by these fires.

Aqua MODIS true color image

According to CNN, there is concern in the Sydney region that these bush fires may conglomerate into one large complex, further threatening the populous New South Wales region. In the case of such an amalgamation, this region would additionally be well-primed for pyroconvection; more updates will come as these fires evolve.

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Original Post:

MTSAT-2 visible channel (left) and shortwave IR channel (right) images (click to play animation)

Numerous bush fires began to burn in state of New South Wales near Sydney, Australia on 16-17 October 2013. On a comparison of MTSAT-2 visible channel and shortwave IR channel images (above; click image to play animation) some of the southeastward-drifting smoke plumes were evident on the visible images, while numerous fire “hot spots” (darker black pixels) could be seen on the shortwave IR images. Toward the end of the animation (at 06:32 UTC on 17 October), the hot fire pixels grew in areal coverage as winds increased in association with a cold frontal passage. Sydney (station identifier YSSY) is at the center of the images.

A 48-hour plot of surface data for Sydney Airport (below) showed that smoke restricted the surface visibility to 4-5 miles from 02-06 UTC on 17 October. Prior to the passage of the cold front, surface air temperatures were unseasonably hot (in the middle 90s F), with wind gusts as high as 38 knots. In addition, note the sharp drop in dew point temperature to -2º F at 04 UTC on 17 October.

Plot of surface data for Sydney, Australia

A 250-meter resolution Aqua MODIS true color image from the NASA EOSDIS Worldview site (below) offers a closer view of the smoke plumes in the Sydney area.

Aqua MODIS true color image

PyroCb Event in British Columbia, Canada

Britta Gjermo | September 15, 2013

GOES-15 Visible and Shortwave IR images (Click image to play animation)

On 15 September 2013, a Pyrocumulonimbus (PyroCb) was detected by GOES-15 imagery in British Columbia, Canada in the center of the province. The animation above is imagery from GOES-15 (click animation to play); the panel on the left is the visible bandwidth and the panel of the right is shortwave infrared bandwidth highlighting the fire hot-spots in black and red pixels. The PryoCb began at 23:30 UTC and continues for the next few hours until 02:30 UTC on 16 September 2013.

GOES-15 Longwave IR (Click image to play animation)

Using the GOES-15 Longwave IR imagery (above, click image to play animation), we were able to see the cloud-top temperatures associated with the PyroCb in the center of image (Latitude: 54 N, Longitude: 126 W) become colder than -40˚C (green color enhancement) after 23:30 UTC and continues until 02:30 UTC. The higher the clouds are, the colder the cloud top temperatures. This PyroCb gets as cold as -55˚C, which is quite impressive for a PyroCb to reach this height in the atmosphere.