Ash fall streak from the Sheveluch volcano in Kamchatka

May 12th, 2019 |

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images, with topography [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images, with topography [click to enlarge]

In a comparison of Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images on 12 May 2019 (above), a dark volcanic ash fall streak was evident in the Visible image, which extended over 100 miles southward from the Sheveluch volcano on the Kamchatka Peninsula of Russia. This feature was a layer of volcanic ash that had been deposited on top of existing snow cover — note that most of the dark ash fall streak exhibited much cooler infrared brightness temperatures compared to the bare ground of the interior valley to the west (since the ash streak existed on top of a higher-altitude area of snow cover).

This ash fall streak was a result of an explosive eruption of the volcano over a month earlier, on 10 April — the volcanic ash plume could be seen moving southward in Himawari-8 Visible (0.64 µm) images (below).

Himawari-8

Himawari-8 “Red” Visible (0.64 µm) images [click to play animation | MP4]

An interesting aspect of this long-lived ash fall streak was that a portion of it was apparently covered by a layer of fresh snowfall at some point after the eruption — and a 7-day sequence of Suomi NPP VIIRS True Color Red-Green-Blue (RGB) images viewed using RealEarth (below) suggested that this layer of new snow was melting with the aid of the high May sun angle, gradually revealing more of the original length of the ash fall streak.

Suomi NPP VIIRS True Color RGB images, 06-12 May 2019 [click to play animation | MP4]

Suomi NPP VIIRS True Color RGB images, 06-12 May 2019 [click to play animation | MP4]

Note that there was another small volcanic plume moving south-southwestward from Sheveluch in the 09 May VIIRS True Color image — retrieved quantities of ash probability, height, loading and effective radius for this volcanic plume (source) are shown below.

Suomi NPP False Color, Ash Probability, Height, Loading and Effective Radius [click to enlarge]

Suomi NPP False Color, Ash Probability, Height, Loading and Effective Radius [click to enlarge]

This type of volcanic ash fall streak frequently occurs on the snow-covered Kamchatka Peninsula — here is an example from March 2013.

Thanks go out to Santiago Gassó for bringing this interesting feature to our attention.

Eruption of Mount Etna in Italy

December 24th, 2018 |

VIIRS True Color RGB images from NOAA-20 (at 1110 and 1220 UTC) and Suomi NPP (at 1200 UTC) [click to enlarge]

VIIRS True Color RGB images from NOAA-20 (at 1110 and 1220 UTC) and Suomi NPP (at 1154 UTC) [click to enlarge]

A sequence of VIIRS True Color Red-Green-Blue (RGB) images from NOAA-20 and Suomi NPP viewed using RealEarth (above) showed the volcanic ash plume from an eruption of Mount Etna in Italy on 24 December 2018.

A toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images (below) revealed a colder cloud plume at higher altitude along the southern edge of the tan/brown volcanic ash plume. A thermal anomaly or “hot spot” (dark black pixels) could be seen at the snow-covered volcano summit.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1250 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1250 UTC [click to enlarge]

The volcanic plume could be quantitatively analyzed using Suomi NPP VIIRS Ash Probability, Ash Height, Ash Loading and Ash Effective Radius products from the NOAA/CIMSS Volcanic Cloud Monitoring site at 1154 UTC (below).

Suomi NPP VIIRS Ash Probability, Ash Height, Ash Loading and Ash Effective Radius at 1154 UTC [click to play enlarge]

Suomi NPP VIIRS Ash Probability, Ash Height, Ash Loading and Ash Effective Radius at 1154 UTC [click to play enlarge]

Since the bulk of the volcanic plume was high in ash content with minimal water or ice cloud, a good signature was seen using Meteosat-11 Split Window (11-12 µm) Brightness Temperature Difference images (below).

Meteosat-11 Split Window (11.12 µm) Brightness Temperature Difference images [click to play animation]

Meteosat-11 Split Window (11.12 µm) Brightness Temperature Difference images [click to play animation]

Eruption of the Anak Krakatau volcano in Indonesia

December 22nd, 2018 |

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, with hourly plots of surface reports from Jakarta (station identifier WIII) [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) showed the volcanic cloud from an eruption of Anak Krakatau in Indonesia on 22 December 2018. Two distinct pulses were evident: the first began around 1340 UTC, with the second starting around 1520 UTC. At times the cloud-top infrared brightness temperatures were -80ºC or colder (violet enhancement) — which roughly corresponded to altitudes around 15-16 km on rawinsonde data from nearby Jakarta (WIII) (below). The eruption process appears to have played a role in generating a tsunami that was responsible for over 400 fatalities — via a partial collapse of the southern flank of the volcano which then triggered an undersea landslide (visualization).

Plots of rawinsonde data from Jakarta, Indonesia [click to enlarge]

Plots of rawinsonde data from Jakarta, Indonesia [click to enlarge]

After sunrise, the volcanic cloud was evident in Himawari-8 “Red” Visible (0.64 µm) images (below) — a toggle between Visible and Infrared images at 0110 UTC showed an example of one of the cold overshooting tops.

Himawari-8 "Red" Visible (0.64 µm) images. with hourly plots of surface reports [click to play animation | MP4]

Himawari-8 “Red” Visible (0.64 µm) images, with hourly plots of surface reports from Jakarta (station identifier WIII) [click to play animation | MP4]

At the onset of the eruption, multi-spectral retrievals from the NOAA/CIMSS Volcanic Cloud Monitoring site showed Ash Height values of 12-14 km and Ash Loading values of 9-10 g/m2 (below). However, after about 1.5 hours the extremely high water and ice content of the volcanic cloud prevented further retrievals of such parameters.

Himawari-8 Ash Height retrievals [click to play animation]

Himawari-8 Ash Height retrievals [click to play animation]

Himawari-8 Ash Loading retrievals [click to play animation]

Himawari-8 Ash Loading retrievals [click to play animation]

A toggle between NOAA-20 VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images viewed using RealEarth (below) showed the volcanic cloud at 0610 UTC on 23 December.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0610 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0610 UTC [click to enlarge]

A comparison of Infrared Window images from NOAA-20 VIIRS (11.45 µm) and Himawari-8 AHI (10.4 µm) at 0610 UTC (below) demonstrated the advantage of improved spatial resolution — the minimum cloud-top infrared brightness temperature of the overshooting top feature was significantly colder on the 375-m resolution VIIRS image (-87ºC, darker shade of violet) than on the corresponding AHI image with 2-km resolution at satellite sub-point (-74.2ºC).

Infrared Window images from NOAA-20 VIIRS (11.45 µm) and Himawari-8 AHI (10.4 µm) [click to enlarge]

0610 UTC Infrared Window images from NOAA-20 VIIRS (11.45 µm) and Himawari-8 AHI (10.4 µm) [click to enlarge]

There was also a significant amount of lightning associated with this volcanic cloud:


A comparison of Himawari-8 Visible and Infrared images showed the persistent volcanic cloud following sunrise on 23 December (below). The pulsing overshooting tops continued to exhibit infrared brightness temperatures as cold as -80ºC at times.

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.4 µm, bottom) images [click to play animation | MP4]

===== 24 December Update =====

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

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

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images (above) provided a detailed view of the volcanic cloud at 0550 UTC on 24 December.

A long animation of Himawari-8 “Clean” Infrared Window (10.4 µm) images spanning over 48 hours from the onset of the eruption (below) showed the remarkably persistent volcanic cloud, with pulsing overshooting tops anchored over Anak Krakatau.

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, with hourly surface report plots from Jakarta WIII {click to play animation | MP4]

===== 25 December Update =====

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

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

In a toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0710 UTC on 25 December (above), a few -90ºC pixels could be seen embedded within the darker purple area of the overshooting top on the Infrared image. Note that there was some westward parallax shift of the image features, due to the scene being near the edge of the VIIRS scan.

The coldest pixels on another NOAA-20 VIIRS Infrared image at 1810 UTC (below) were still within the -80 to -87ºC range.

NOAA-20 VIIRS Infrared Window (11.45 µm) image [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) image [click to enlarge]

An updated long animation of Himawari-8 Infrared images (below) continued to show periodic bursts of cold pixels within overshooting tops above the eruption site.

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, 22-25 December [click to play MP4 animation]

===== 28 December Update =====

Himawari-8 "Clean" Infrared Window (10.4 µm) images, 22-28 December [click to play MP4 animation]

Himawari-8 “Clean” Infrared Window (10.4 µm) images, 22-28 December [click to play MP4 animation]

An updated long animation of Himawari-8 Infrared images (above) revealed that the volcanic thunderstorm — which had persisted over the eruption site nearly continuously since 1350 UTC on 22 December — underwent its final pulse around 0640 UTC on 28 December, and was no longer seen after 0900 UTC. The volcanic thunderstorm began its transition from being nearly continuous to a phase of discrete discontinuous pulses after about 0500 UTC on 27 December; the last image with cloud-top infrared brightness temperatures of -80ºC or colder was 2110 UTC on that day.

NOAA-20 captured one of the final convective pulses around 0620 UTC on 28 December (below), when the coldest cloud tops were in the -50 to -55ºC range (yellow to orange enhancement).

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

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



Eruption of Mount Veniaminof on the Alaska Peninsula

November 21st, 2018 |
GOES-17

GOES-17 “Red” Visible (0.64 µm) and Split Window Difference (10.3-12.3 µm) images [click to play MP4 animation]

* GOES-17 images posted here are preliminary and non-operational *

Following an eruption of Mount Veniaminof on 21 November 2018, 1-minute Mesoscale Domain Sector GOES-17 “Red” Visible (0.64 µm) and Split Window Difference (10.3-12.3 µm) images (above) showed the volcanic ash plume drifting southeastward over the Gulf of Alaska. During the period 1947-2323 UTC the plume was seen to grow to a length of 200 miles from the volcano summit. Note in the Visible imagery that the 2625 ft (800 m) volcano acted as a barrier to the northwesterly boundary layer winds to create a cloud-free “notch” immediately downwind of Veniaminof.

NOAA-20 VIIRS True Color RGB images viewed using RealEarth (below) highlighted the light brown color of the ash plume.

NOAA-20 VIIRS True Color RGB images [click to enlarge]

NOAA-20 VIIRS True Color RGB images [click to enlarge]

A sequence of retrieved Ash Probability, Ash Height and Ash Loading (source) derived from Terra/Aqua MODIS and Suomi NPP VIIRS data (below) indicated high probabilities of ash content, height values primarily in the 4-6 km range and ash loading exceeding 4 g/m3 at times.

Terra/Aqua MODIS and Suomi NPP VIIRS Ash Probability, Ash Height and Ash Loading images [click to play animation | MP4]

Terra/Aqua MODIS and Suomi NPP VIIRS Ash Probability, Ash Height and Ash Loading images [click to play animation | MP4]