Eruption of Mount Shishaldin in Alaska

January 19th, 2020 |

Topography along with Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 1323 UTC [click to enlarge]

Topography along with Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 1323 UTC [click to enlarge]

Following two days of increasing seismicity, Mount Shishaldin began a period of more intense eruptive activity around 0930 UTC on 19 January 2020 — a comparison of topography along with Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 1323 UTC (above) displayed a distinct thermal anomaly (cluster of red 3.74 µm pixels) and a volcanic cloud moving east-southeastward.

Comparisons of Shortwave Infrared and Infrared Window images from Suomi NPP VIIRS and GOES-17 ABI (below) revealed a parallax shift that is inherent with geostationary imagery at high latitudes.

Comparison of Shortwave Infrared images from Suomi NPP VIIRS (3.74 um) and GOES-17 ABI (3.9 um) [click to enlarge]

Comparison of Shortwave Infrared images from Suomi NPP VIIRS (3.74 µm) and GOES-17 ABI (3.9 µm) [click to enlarge]

Comparison of Infrared Window images from Suomi NPP VIIRS (11.45 µm) and GOES-17 ABI (10.35 µm) [click to enlarge]

Comparison of Infrared Window images from Suomi NPP VIIRS (11.45 µm) and GOES-17 ABI (10.35 µm) [click to enlarge]

A toggle between GOES-17 parallax correction vectors and magnitudes for cloud top heights of 15,000 feet (4.5 km) and 30,000 feet (9.1 km) are shown below —  the amount of northwestward volcanic cloud displacement between the Suomi NPP and GOES-17 Infrared images roughly matched the 16 km (or 10 mile) value for a 15,000 foot cloud top in that region of the Full Disk. Later advisories listed the maximum ash height at 20,000-30,0000 feet.

GOES-17 parallax correction vectors (green) and magnitudes (km, red) [click to enlarge]

GOES-17 parallax correction vectors (green) and magnitudes (km, red) [click to enlarge]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) Split Cloud Top Phase (11.2 – 8.4 µm) images (below) displayed an increasing volcanic ash signal (negative values, darker blue to violet enhancement) beginning around 01 UTC on 20 January. Some light ash fall was reported at False Pass, Alaska.

GOES-17 Split Cloud Top Phase (11.2 - 8.4 um) images [click to play animation | MP4]

GOES-17 Split Cloud Top Phase (11.2 – 8.4 µm) images [click to play animation | MP4]

10-minute images of GOES-17 radiometrially retreived Ash Height from the NOAA/CIMSS Volcanic Cloud monitoring site (below) indicated that the bulk of the ash plume existed within the 2-6 km altitude range.

GOES-17 Ash Height product [click to play animation | MP4]

GOES-17 Ash Height product [click to play animation | MP4]

In corresponding GOES-17 False Color Red-Green-Blue (RGB) images (below), the volcanic plume exhibited shades of red/magenta/pink — the characteristic signature of an ash-laden cloud.

GOES-17 False Color RGB [click to play animation | MP4]

GOES-17 False Color RGB [click to play animation | MP4]

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