Satellite imagery and multiple earthquakes near American Samoa

August 25th, 2022 |
False Color imagery over the American Samoa sector, 1610 UTC on 25 August 2022 (Click to enlarge)

Seismic activity has been ongoing in August 2022 beneath the island of Ta’u to the east of American Samoa. (USGS has published a variety of information on this swarm of Earthquakes: link 1; link 2; link 3); See also these two recorded Facebook Live presentations from the NWS WSO office in Pago Pago: (August 22nd and August 17th). Volcano updates fro Ta’u can also be viewed here.

The Volcanic Ash Advisory Center (VAAC) that has responsibility for this region of the south Pacific is Wellington NZ. Click here for a pdf that shows all VAAC boundaries.

Should an eruption occur (NOTE: An eruption is not expected in the near term!), what kind of satellite information will be useful? The Volcanic Cloud Monitoring website (link) from CIMSS includes imagery over various sectors on Earth, sorted by VAAC. For American Samoa, and adjacent regions, Choose ‘Satellite Imagery’ and under the ‘Sector’ menu, and then choose, under the Wellington VAAC subsection, ‘American Samoa (750 m)’ Both GOES-17 / GOES-18 and Himawari view the region, but GOES-17/GOES-18 sub-satellite points are closer to American Samoa and will provide better resolution views. (NOAA-20 and Suomi-NPP as polar orbiters will provide the highest spatial resolution data, but have poor temporal resolution). You can choose various image types at the website: quantitative estimates of Ash Loading, Ash Height, Ash Loading, Ash Reflectivity, Single-channel Brightness Temperatures (or Reflectivity), and various Red/Green/Blue composites. Note that this website has an extensive explanatory section (under the ‘Tutorials’ tab) to help you understand what you’re seeing in the imagery. The GOES-18 false-color image red/green/blue image, above, is the from the website. An eruption is not occurring, nor detected, in the image.

Various websites also allow views of Satellite Imagery over the region. For example, the CSPP Geosphere site includes True-Color imagery (day) and Night time Microphysics (night) by default, but also allows a user to view single channels. (Direct link, see an example below) There is also a NOAA/NESDIS site that includes some RGBs and each of the individual bands; the CIRA Slider also includes imagery over the south Pacific.

Night Microphysics RGB near American Samoa, 1700 UTC on 25 August 2022 (Click to enlarge)

Wind direction will be important if an eruption occurs (this is at present unlikely!!) to know as that will control the dispersion of any gases. The windy.com website will provide this with this link.


This blog entry is meant to be a resource should an eruption occur. (Note: that is not expected!) For more information, please refer to the USGS website, and the American Samoa Facebook page.

Explosive eruption of the Hunga Tonga volcano

January 15th, 2022 |

JMA Himawari-8 True Color RGB images [click to play animated GIF | MP4]

JMA Himawari-8 True Color RGB images created using Geo2Grid (above) showed the rapid expansion of a volcanic cloud following an explosive eruption of Hunga Tonga on 15 January 2022. An abrupt shock wave was also evident, which propagated radially outward in all directions.

The volcanic cloud also exhibited a striking appearance in GOES-17 (GOES-West) “Clean” Infrared Window (10.35 µm) images (below), with a pronounced arc of cloud-top gravity waves along its eastern edge as the bulk of the cloud material drifted westward. Pulsing concentric shock waves were also seen in the infrared imagery.

GOES-17 “Clean” Infrared Window (10.35 µm) images (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click to play animated GIF | MP4]

The explosive nature of the eruption could be seen by examining 10-minute GOES-17 Visible and Infrared images  during the first 30 minutes (below) — only 20 minutes after the 0400 UTC eruption onset, the infrared cloud-top brightness temperature had already cooled to -100ºC (placing it in the lower stratosphere).     

GOES-17 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.35 µm, right) images [click to play animated GIF | MP4]

Beginning at 0705 UTC, a GOES-17 Mesoscale Domain Sector was positioned over the region, providing imagery at 1-minute intervals — Infrared images during the period 0705-1200 UTC are shown below. The crescent-shaped area of “bow shock wave” ripples persisted, due to the robust and dense volcanic cloud acting as an obstacle to the easterly winds within the stratosphere.  The 1-minute imaging was also able to capture the brief pulse of an overshooting top which exhibited an infrared brightness temperature of -105.18ºC at 0841 UTC (zoomed-in animation: GIF | MP4) — which could be a record cold cloud-top temperature, as sensed from a geostationary satellite (see this blog post). 

GOES-17 “Clean” Infrared Window (10.35 µm) images [click to play animated GIF | MP4]

A plot of 1-minute GOES-17 overshooting top infrared brightness temperatures (IRBTs) along with 10-minute Full Disk GOES-17 and Himawari-8 IRBTs (below) showed that the brief cold 0841 UTC overshooting top (and its rapid collapse) occurred between the times of routine 10-minute Full Disk scans — highlighting the value of rapid scan 1-minute imagery. 

Plot of 1-minute GOES-17 overshooting top infrared brightness temperatures (IRBTs), along with 10-minute Full Disk GOES-17 and Himawari-8 IRBTs [click to enlarge]

VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi-NPP, viewed using RealEarth (below), also showed the region of cloud-top gravity waves (with minimal parallax compared to GOES-17) .  

VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi-NPP [click to enlarge]

Plot of 00 UTC rawinsonde data from Nandi, Fuji [click to enlarge]

Satellite-based lidar and limb sounder data indicated that the volcanic cloud reached maximum altitudes around 30-32 km — well into the lower stratosphere, where easterly winds existed according to 00 UTC rawinsonde data from Nandi, Fiji (above). The westward drift of most of the volcanic cloud as seen in a Suomi-NPP VIIRS Day/Night Band (0.7 µm) image (below) lined up well with wind barbs at 30 hPa (an altitude of 23.78 km on the Nandi NFFN sounding). 

Suomi-NPP VIIRS Day/Night Band (0.7 µm) image, with 30 hPa wind barbs plotted in violet and rawinsonde sites plotted in yellow [click to enlarge]

GOES-17 Mid-level Water Vapor (6.9 µm) Time Difference images (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click to play animated GIF | MP4]

Propagation of the volcanic shock wave across the Pacific Ocean could be followed in GOES-17 (GOES-West) Mid-level Water Vapor (6.9 µm) Time Difference images (above). As the shock wave continued to propagate farther eastward across North/South America and then the Atlantic Ocean, the wave front could be seen in GOES-16 (GOES-East) Water Vapor Time Difference images (below). As the shock wave moved across southern Wisconsin, a brief rise/fall couplet in surface air pressure just prior to 1500 UTC (9:00 am CDT) was evident in plots from the University of Wisconsin – Madison’s Atmospheric, Oceanic and Space Sciences building rooftop tower (as well as the personal weather station of the author of this blog post).

GOES-16 Mid-level Water Vapor (6.9 µm) Time Difference images (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click to play animated GIF | MP4]


GOES-17 and Himawari-8 visible imagery can be combined to create stereoscopic imagery of the eruption, as shown below.

GOES-17 Visible (Band 2, 0.64 µm) imagery, left, and Himawari-8 Visible (Band 3, 0.64 µm) imagery, right, 0400-0500 on 15 January 2022 (Click to enlarge)

Hunga Tonga erupts again

January 13th, 2022 |

GOES-17 imagery revealed another explosive eruption of Hunga Tonga-Hunga Ha?apai in the south Pacific Ocean between 1500 and 1530 UTC on 13 January 2022; an eruption in December 2021 is discussed here. The brightness temperatures in this volcanic plume cooled from -9.4o to -66.7o between 1520 and 1530 UTC. This 1308 UTC NUCAPS profile from 20.5oS / 175.5o W (the profile location is shown here) suggests the plume rose from 445 mb to 188 mb in those 10 minutes (or from 20 thousand to 39 thousand feet).

GOES-17 Clean Window*(see below) (Band 13, 10.3 µm) Infrared Imagery, 1500-1940 UTC on 13 January 2022 (Click to enlarge)

Imagery at 2100 UTC, below, shows the extent of the plume in the visible.

GOES-17 Visible (Band 2, 0.64 µm) Imagery, 2100 UTC on 13 January 2022 (Click to enlarge)

Computed Ash/Dust Cloud Heights, below, from 1510-1600 UTC on 13 January, available at the CIMSS Volcanic Cloud Monitoring Web Portal (link, search under the Wellington VAAC for Hunga Tonga), shows the rapid increase in height, to above 16 km, as well.

Retrieved Cloud Heights, 1510 – 1600 UTC on 13 January 2022 (Click to enlarge)

An animation of GOES-17 visible imagery, below, (courtesy Scott Bachmeier, CIMSS) shows the evolution of the pulsing eruption throughout the day on 13 January.

GOES-17 Visible (0.64 µm) imagery, 1700 UTC 13 January – 0010 UTC 14 January 2022 (Click to enlarge)

* You might notice that this AWIPS Full Disk imagery is at full resolution! In NWS Forecast Offices, full-disk imagery in AWIPS is degraded to 6-km resolution, meaning that interesting events outside of GOES-16 CONUS (or GOES-17 PACUS) that do not fall within a mesoscale sector can only be shown such that they’re zoomed out (as in this tweet from WFO Seattle about this event). The full-res imagery herein was created by inputting the full-resolution full-disk imagery (obtained at CIMSS from the GRB datastream) into AWIPS, replacing the subsected data.

Eruption of Volcán Wolf in the Galápagos Islands

January 7th, 2022 |

GOES-16 Ash RGB images [click to play animated GIF | MP4]

GOES-16 Ash RGB images created using Geo2Grid (above) displayed the expansion of 2 volcanic clouds following the eruption of Wolf in the Galápagos Islands on 07 January 2022 — one moving northeastward and dissipating, and the other moving westward. The green shades of the volcanic cloud suggested that it contained fairly high concentrations of SO2 (in contrast to volcanic ash, would would appear as shades of pink/magenta). The cluster of dark blue pixels represented the hot thermal anomaly at the summit of the volcano, which persisted during the entire day.

This persistent thermal anomaly was also apparent in Shortwave Infrared (3.9 µm) images from GOES-17 (GOES-West) and GOES-16 (GOES-East) (below), shown in the native projection of each satellite.

Shortwave Infrared (3.9 µm) images from GOES-17 (left) and GOES-16 (right) [click to play animated GIF | MP4]