PyroCb near Perth in Western Australia

Himawari-8 Shortwave Infrared (3.9 µm, left) and Visible (0.64 µm, right) images [click to play animation]

Himawari-8 Shortwave Infrared (3.9 µm, left) and Visible (0.64 µm, right) images [click to play animation]

A 2-panel comparison of Himawari-8 Shortwave Infrared (3.9 µm) and Visible (0.64 µm) images (above) showed the “hot spot” (red pixels) associated with a large bush fire burning near Waroona (south of Perth) in Western Australia on 06 January 2016 (media report), along with smoke from the fire and the explosive development of a pyroCb cloud after about 0830 UTC. The variation in smoke transport was explained by the strong vertical wind shear profile seen on a plot of 12 UTC Perth rawinsonde data: easterly winds within the 800m-2000m layer were carrying smoke westward off the coast, while smoke transported to higher altitudes by the pyroCb cloud was drifting southeastward due to northwesterly flow aloft.

Himiwari-8 Infrared (10.4 µm) images (below) indicated that cloud-top IR brightness temperatures cooled to -40º C (bright green color enhancement) around 0830 UTC, eventually reaching a minimum of -56º C (darker orange color enhancement). According to analysis performed by René Servranckx, the coldest cloud-top IR brightness temperature detected by the AVHRR instrument on NOAA-18 was -61.2º C at 1104 UTC (which corresponds to an altitude of 14 km based upon the Perth rawinsonde data).

Himawari-8 Infrared (10.4 µm) images [click to play animation]

Himawari-8 Infrared (10.4 µm) images [click to play animation]

During the nighttime hours following the initial pyroCb development, the fire raced westward as revealed by the spreading out of the red pixels on Himawari-8 Shortwave IR (3.9 µm) images and the light gray to brighter white pixels on Near-IR (2.3 µm) images (below).

Himawari-8 Shortwave IR (3.9 µm) images [click to play animation]

Himawari-8 Shortwave IR (3.9 µm) images [click to play animation]

Himawari-8 Near-IR (2.3 µm) images [click to play animation]

Himawari-8 Near-IR (2.3 µm) images [click to play animation]

On 07 January, two additional pyroCb clouds were seen to develop from the Waroona fire: the first after about 03 UTC, and the second after about 06 UTC. In this case, the pyroCb cloud material was transported rapidly eastward, as seen in Himawari-8 Infrared (10.4 µm) images (below), due to an increase in westerly winds aloft as seen in a plot of 00 UTC Perth rawinsonde data. An animation of Himawari-8 true-color images showing these 2 pyroCb events can be seen here.

Himawari-8 Infrared (10.4 µm) images [click to play animation]

Himawari-8 Infrared (10.4 µm) images [click to play animation]

A comparison of Suomi NPP VIIRS true-color images from 06 January and 07 January (below) showed an increase in the thickness and areal coverage of smoke aloft over the region (Note: the actual overpass times of the Suomi NPP satellite were between 06 and 07 UTC, as seen here and here). A plot of VIIRS-detected fire locations (red dots) for the period ending at 12 UTC on 07 January is also shown.

Suomi NPP VIIRS true-color images from 06 January and 07 January [click image to enlarge]

Suomi NPP VIIRS true-color images from 06 January and 07 January [click image to enlarge]

To further investigate the transport of smoke from this fire CALIPSO was used. This LIDAR shows the height of the clouds from the wildfire. The first image below is the 532nm Total Attenuated Backscatter plot on 07 January from 05:37 UTC to 6:00 UTC. The smoke from this fires can be seen ~ 32 S indicated faintly by a red/grey color. The second image is 1064 nm Total Attenuated Backscatter plot, the smoke on this plot is indicated by a grey color. The third image is the Depolarization image the smoke is indicated by a red color. The fourth image is the Attenuated Ratio plot between 1064 nm and 532 nm. The smoke is indicated by the light blue pixels. The fifth image is the Vertical Feature Mask. This plot shows the different features that are in the atmosphere, the smoke is attributed as a cloud on this plot and is indicated by a light blue color.
2016-01-07_04-30-00_Exp_V3.30_4_1CALIPSO 532 nm Total Attenuated Backscatter on 07 January (click to enlarge)

2016-01-07_04-30-00_Exp_V3.30_4_4CALIPSO 1064 nm Total Attenuated Backscatter on 07 January (click to enlarge)

2016-01-07_04-30-00_Exp_V3.30_4_3CALIPSO Depolarization Ration on 07 January (click to enlarge)

2016-01-07_04-30-00_Exp_V3.30_4_5CALIPSO Attenuated Color Ratio between 1064 nm and 532 nm on 07 January (click to enlarge image)

2016-01-07_04-30-00_Exp_V3.30_4_6CALIPSO Vertical Feature Mask on 07 January (click to enlarge image)

Below is an animation of the convergence at 250 mb shown by a color fill, the the 250 mb geopotential height contoured every 30 meters and the wind barbs.It has been investigated that upper level divergence is associated with the ability for pyroCu to turn into a pyroCb (Peterson et al., BAMS, Feb. 2015, 229-247). Starting at 0 UTC on 06 January the spot of the pyroCbs are indicated by the white dots. These pyroCbs are in an area of divergence indicated by the light blue and dark green color. This is conducive to the strengthening of the pyroCb. If there is divergence at upper levels there is rising air below that area of divergence. These conditions are favorable to the pyroCb developing.


250 mb Convergence(color fill), Geopotential Height (contoured every 30 m) and wind barbs every 6 hours starting on 06 January 0 UTC.

This Skew-T taken at 12 UTC on 06 January after the pyroCb located at 32.9 S 116 E. From the Skew-T it is apparent that there is a very dry air above this pyroCb.
106skewtSkew-T at 12 UTC (click to enlarge) Green line is dew point and red line is temperature.

This Skew-T taken at 12 UTC on 07 January after the pyroCb located at 32.9 S 116 E. From the Skew-T it is apparent that there is a very dry air above this pyroCb, but becomes very moist above 300 mb. This moist air could be beneficial to the develop of the pyroCbs at this time.
107skewtSkew-T at 12 UTC (click to enlarge) Green line is dew point and red line is temperature.

Leave a Reply

Your email address will not be published.