Grassland fire in Mongolia generates a pyrocumulonimbus cloud

April 19th, 2022 |

JMA Himawari-8 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.4 µm, bottom) images [click to play animated GIF | MP4]

JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed signatures of a rapidly-spreading grassland fire in eastern Mongolia’s Numrug National Park (near the border with China) on 19 April 2022. The fast rate of northeastward growth of the dark burn scar in Visible imagery was particularly striking. Strong winds aided the rapid expansion of this fire, due to the tight pressure gradient between a high over central China and a deepening low that was moving from Siberia to northeastern China (surface analyses).

Consecutive NOAA-20 VIIRS Infrared image valid at 0401 UTC and 0541 UTC — viewed using RealEarth (below) — showed the eastward drift of individual small pyrocumulonimbus (pyroCb) clouds, which exhibited cloud-top infrared brightness temperatures of -40ºC and colder (brighter green color enhancement).

NOAA-20 VIIRS Infrared Window (11.45 µm) images at 0401 UTC and 0541 UTC [click to enlarge]

A toggle between NOAA-20 VIIRS True Color RGB and Infrared images at 0541 UTC (below) depicted the dark burn scar as well as the smoke plume with embedded pyroCb clouds.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0541 UTC [click to enlarge]

30-meter resolution Landsat-8 False Color RGB imagery valid at 0252 UTC (below) provided an even more detailed view of the dark burn scar — in addition, the active fire front appeared as brighter shades of pink to red along the eastern and southeastern flanks.

Landsat-8 False Color image at 0252 UTC [click to enlarge]

After sunset, the northern flank of the fire continued to burn at an intense rate, judging from the thermal signature seen in Himawari-8 Shortwave Infrared images (below). Dense layered clouds began to move over the region before sunrise the next day, which then acted to mask the fire’s thermal signature.

JMA Himawari-8 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.4 µm, bottom) images [click to play animated GIF | MP4]

A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images valid at 1757 UTC (below) showed the bright nighttime glow of active fires — especially along the aforementioned northern flank — in addition to the associated smoke plume that was moving eastward, as illuminated by the Moon (which was in the Waning Gibbous phase, at 90% of Full). This smoke did not exhibit a signature in the corresponding 11.45 µm Infrared image, since relatively thin smoke layers are generally transparent to upwelling surface radiation at longer wavelengths.

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1742 UTC [click to enlarge]

GOES-17 imagery and a cooler Set Point temperature

April 19th, 2022 |
GOES-17 Band 10 Infrared (Upper Level water vapor imagery, 7.34) imagery, 1531 UT on 19 April 2022 (Click to enlarge)

At 1500 UTC today, the Set Point temperature on the cryocooler was re-set to a cooler temperature (the effect of the warmer Set Point temperature is discussed here: Bands 10 and 12 had more lines of missing data related to the warming of the satellite by the Sun). The cryocooler works to reduce the thermal load on the satellite, but during seasonal peak heating (see the figure on Page 5 in this document), it is unable to counteract fully the effects of the malfunctioning Loop Heat Pipe on GOES-17.

The figure below compares Focal Plane Temperatures on 16 April (with the warmer Set Point temperature) and 19 April (during which day the cooler Set Point Temperature was re-implemented). (More comparison imagery is at this website; imagery for Band 10 on 16 April is here; from 19 April is here) Note how the brightness temperature difference between GOES-16 and GOES-17 is very different (one might say noisy) on 16 April, and on 19 April until about 1530 UTC, after which point it stabilizes at less than about 0.25K warmer for GOES-17. The change in the Focal Plane Module (FPM) Temperature is also apparent: The FPM is about 3K cooler than on 16 April starting around 1500 UTC on 19 April. This is because of the change in the Set Point on the cryocooler that occurred at that time.

GOES-17/GOES-16 brightness temperature differences within a small region (Blue stars/line) and Focal Plane Temperature (Black Line/magenta stars) from 0000-1730 UTC on 16 and 19 April 2022 (Click to enlarge)

NUCAPS fields over American Samoa

April 19th, 2022 |
Sounding Availability fields over the South Pacific, 1234 UTC on 19 April 2022. Note the two green dots to the north and south of American Samoa (Click to enlarge)

Oceans such as the South Pacific can be a large data void. NOAA-20 NUCAPS profiles can be an important data source to define the state of the atmosphere. The image above shows NUCAPS Sounding Availability from the overnight pass over American Samoa; the largest island of American Samoa, Tutuila, is just west of 170oW in image above. There are green circles just north and just south of Tutuila, signifying locations of NUCAPS profiles associated with successful retrievals. The toggle below compares those two profiles with the 1200 UTC rawinsonde launch (NSTU) from Pago Pago. Good agreement is apparent, although the NUCAPS profiles are smoother.

NUCAPS soundings just north and south of American Samoa (1308 UTC), and the 1200 UTC Radiosonde at NSTU, 19 April 2022 (Click to enlarge)

The environment is somewhat dry. This is confirmed by a MIMIC Total Precipitable water mapping, shown below (for 1200 UTC on 19 April 2022) in an image taken from here. The Samoan islands are between two bands of moisture.

MIMIC Total Precipitable Water, 1200 UTC on 19 April 2022

NUCAPS profiles give useful information, but it can be cumbersome to view all individual profiles sequentially. Gridded fields of various properties are available in AWIPS (and online here and here). The toggle below shows a larger view than the topmost image, and it compares gridded Temperature fields at 950 mb, and the 950-700 mb lapse rate. Over the Samoan islands, 950-mb temperatures are faily uniform around 23o C, with “cooler” temperatures (closer to 21o C) just to the northeast. Lapse rates are stable: between 4 and 5 oC/km. As you might expect given the relative dryness and stability, shower chances over American Samoa for 19 April are low.

NUCAPS Soundings Availability points over the South Pacific, along with gridded fields of 950-mb Temperature, and 950-700mb Lapse Rates (Click to enlarge)

Use NUCAPS when your weather is approaching from a region void of conventional data.

Imagery in this blog post was in part from the NOAA/TOWR-S instance of AWIPS in the Cloud. Thank you!