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).

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.

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.

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.

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.

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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.

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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 170^oW 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.

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.

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 23^o C, with “cooler” temperatures (closer to 21^o 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.

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

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

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The month-long animation above shows the Himawari-8 Sandwich Product (daytime, blending visible band 3 (0.64 µm) and Band 13 (10.41 µm); and nighttime: Infrared only (Band 13, 10.41 µm) ) for the period from 16 March 2021 through 16 April 2021 over the Pacific Island (1) sector from this site, courtesy of JMA. How has the tropical western Pacific changed over this month? During the first week, mid-latitude extratropical fronts move west to east across the northern part of the domain, brushing the northern Marianas Islands. The monsoon trough over the southern part of the domain shows a lot of activity from the start of an animation, although some periods show more activity than others (25-28 March is quiescent compared to times before and after). A cyclonic circulation moves westward to the south of Guam on 31 March/1 April. Then a stronger impulse moves into the domain from the east on 2-3 April. By 7 April, this tropical storm is south of Guam moving towards the northwest where it becomes Typhoon Malakas. An obvious eye is apparent in that system as it recurves to the west of Guam on 12-13 April. By the end of the animation (17 April), the system has lifted to the north/east of this domain, and the sector has only scattered convection.

Note in particular as the animation occurs how the region of Sun glint has shifted northward. Northern Hemisphere Spring is ongoing.

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