Eruption of the Anak Krakatau volcano in Indonesia

By Scott Bachmeier • 22 December 2018

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]

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 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]

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).

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:

#Krakatoa/#Krakatau #lightning update: Rough counts have had peak values of 90 lightning events per minute detected around the volcano! Between ~1430 UTC 22 Dec and ~1900 UTC 23 Dec, there have been tens of thousands of lightning events detected by GLD360. pic.twitter.com/iekphVjsD2

— Chris Vagasky (@COweatherman) December 23, 2018

Here’s the @WWLLN lightning strike detection map for #Krakatau on Dec 23: 10856 strokes. Remarkable. pic.twitter.com/6xxdYSgjmu

— Simon Carn (@simoncarn) December 24, 2018

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 “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 (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 “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]

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]

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 “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]

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]

Here it is…a loop of #lightning from 2:30am MT 22 Dec until 2:30am MT 28 December from #Krakatau/#Krakatoa detected by GLD360. A truly incredible event. pic.twitter.com/nvStqoMaAC

— Chris Vagasky (@COweatherman) December 28, 2018

Categories: Himawari-8, Lightning, NOAA-20, RealEarth, Red-Green-Blue (RGB) images, VIIRS, Volcanic activity

CIMSS Satellite Blog

CIMSS Satellite Blog

Eruption of the Anak Krakatau volcano in Indonesia