There were a series of spectacular eruptions from the Indonesian volcano Sangeang Api at the end of the May.
22 October 2020
30 May 2014
The volcano underwent a sustained, significant eruption on 30 May, resulting in large masses of volcanic ash being ejected into the sky.
The ash cloud grounded flights between Australia and south-east Asia, and all domestic flights from Darwin airport in the north of the country.
by HansPeter Roesli (Switzerland)
The Figure 1 comparison slider below shows two Metop-B images taken some seven hours after the first eruption on 30 May. The first image is the split-window difference (SWDF) (IR11-IR12) and enhances in yellow-to-red colours the negative differences coming mainly from volcanic ash (and other spurious sources). The positive differences are enhanced from black to white.
The second image is the Night Microphysics RGB composite, but taken during the day. Here the stronger pink colour is ash, while the brown-coloured feature lower right is ice cloud.
The video of hourly images from MTSAT-2 again uses the SWDF scheme (the only scheme enhancing ash over 24 hours available from MTSAT's channels). The sequence starts just before the first eruption.
This ash cloud drifts into Central Australia (at ~100km/h) where it then disappears (the yellow colour coming up from SW-Australia is due to differential emission by the land surface).
A second longer eruption started on 30 May after 17:30 UTC and ended on 31 May towards 12:00 UTC. It was followed by smaller puffs. By 1st June major activities had stopped.
The three VIIRS images (Figures 2–4) are from 30 May, 17:45 UTC, shortly after the start of the second eruption. They are Volcanic Ash and SO2 . Figure 5 is a composite of the Suomi-NPP Day-Night Band and the IR11.4, also from 30 May, 17:45 UTC.
The image shows the ash cloud from the first eruption. The ash cloud can be seen off the Australian coast, at the end of a long pink tail.
The image is the zoomed-in version of Figure 2.
The image is a close-up of the volcano area with the fresh multi-coloured eruption cloud.
Brown colours represent iced tops of thick cloud, black are thin ice cloud (the green hue might be an indication of the presence of SO2), pink areas are from volcanic ash, and the yellow parts are again ash, possibly mixed with SO2.
Composite of the Day-Night Band (DNB, red-to-yellow) at 750m resolution and the IR11.45 (I5, colour scale at the top) channel at 375m resolution.
The DNB clearly shows two craters. The brighter one was emanating the big plume with temperature values down to -196.5 K (76.6 °C) at the top. The secondary crater was emanating some material, but at much lower level so could hardly be seen.
The overpass of Metop-B's IASI sensor seven hours after the start of the eruption allows for the retrieval of SO2 and ash signals. Using simple spectral-line differences (absorption on/off) the presence of SO2 and ash from the eruption can be clearly seen in Figure 6.
At the time of observation ash was still flowing out of the volcano forming a meandering plume. SO2 emission appears to have stopped earlier on and its cloud has drifted east-southeastward. Comparing the distribution of the two species, SO2 was mixed with ash, but not the other way round.
Eruption of the Sangeang Api volcano in Indonesia (CIMSS Blog)
MODIS imagery (NASA Earth Observatory)
News.com-au story on the eruption
Mt. Sangeang Api continues to erupt (Jarkarta Post)
Pictured from a passenger plane: Menacing 12-mile-high ash cloud looms over Indonesia's 'Mountain of Spirits' after volcano erupts (Daily Mail)
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