Can Geostationary Imagers See Noctilucent Clouds?

June 20th, 2022 |

Q: Can geostationary imagers see the very thin, very high Noctilucent Clouds? A: Yes and no, depending on the satellite, how data are processed, time of the year, time of the day and spectral band. Thanks to Simon Proud for this tweet using JMA‘s Advanced Himawari Imager (AHI):

Note the very thin line near the top of the images on June 20, 2022. These images are derived from Japan’s AHI. A animated gif version.
A similar loop as above, but more zoomed in. From June 20, 2022. These images are derived from Japan’s AHI. An animated gif version.
A “spectral” loop of AHI’s three visible bands at 15 UTC on June 20, 2022. A animated gif version.

Since NOAA’s ABI is a similar instrument to AHI it seems likely that ABI can also observe noctilucent clouds at times. Noctilucent clouds are possibly only observable in visible bands when they are off the earth’s edge, with space as a background, and when illuminated from certain angles. However, due to ground system processing in the generation of the ABI radiance files, most users cannot see data that the ABI scans off the Earth’s edge in space. Special processing of ABI data does allow to show off Earth pixels, such as in these examples with the moon and the Webb Space Telescope plume in space. Recall that the AHI Full Disk is made up of 23 swaths (as opposed to 22 for the ABI), so it scans a bit more space both north and south of the Earth.

An animation including the AHI 3.9 micrometer band shows the relationship between the Earth’s edge and the apparent cloud location. (A animated gif version.) Consider also the large apparent displacement of these high altitude (“shining at night”) clouds due to parallax.

Also see this image:

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]

A month of Himawari imagery over Guam

April 18th, 2022 |

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.

ACSPO SSTs from Himawari-8 in AWIPS

April 15th, 2022 |
Himawari-8 Band 3 (0.64 µm) visible imagery overlain on top of ACSPO SSTs derived from Himawari-8 data, toggled with Himawari-8 Band 13 (10.41 µm) infrared imagery, 0800 UTC on 15 April 2022 (Click to enlarge)

The image above toggles between Advanced Clear-Sky Processor for Ocean (ACSPO) sea-surface temperatures (created with AHI data from Himawari-8) overlain with AHI Band 3 (0.64 µm) visible imagery, and AHI Band 13 (10.41 µm) clean window infrared imagery. Sheared tropical Storm Malakas — in the midst of transition to an extratropical storm — is apparent in the upper center of the imagery. The SST color enhancement is such that violet temperatures show were SSTs exceed 27o C. Malakas is now over ocean water with a temperatures of around 20o C.