On 13 February the Indonesian volcano Kelut (also known as Kelud) exploded with a powerful eruption which was seen by a number of satellites.
22 October 2020
13 February 2014
Satellites first detected the eruption plume at 16:09 UTC. Then at 17:30 UTC, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite acquired images of an umbrella or mushroom-shaped ash plume above the cloud deck.
The ash fall was significant and widespread — the village Pandan Sari (Ngantang) is totally destroyed; at least four people died and all three major airports, Surabaya, Solo and Yogyakarta, were closed.
by Martin Setvak (CHMI ) and Jochen Kerkmann (EUMETSAT)
On 13 February the VIIRS instrument on the Suomi NPP satellite captured a large umbrella cloud, that resembled a convective storm with a cold-ring feature, which formed above Kelut volcano after its massive eruption.
The images below show the low-light capabilities of the VIIRS instrument, namely its Day-Night band (DNB). The DNB image is combined with color-enhanced 11.45 microns 375 m band image to create the so-called 'sandwich product'. While the sandwich products are typically used in daytime, to show details of tops of convective storms, the sandwich image utilizes reflected light of the almost full Moon, illuminating this nocturnal scene.
Figure 1: Regular DNB image
As the volcano cloud was composed of large number of ash particles, it was noticeably darker compared to normal clouds around it. As well as the clouds themselves, some city lights could be seen around, where the sky was clear.
This cropped image of a larger area better shows the colour difference between the ash cloud (dark grey) and regular clouds (white).
Figure 2: HDR-merged DNB images
To show as much details as possible, the Figure 2 was created using the HDR technique, combining two differently processed DN images. These two input images were HDR-merged in Photoshop CS5, where fine-tuning the HDR output was done. As result, the volcanic cloud appeared as bright as the surrounding clouds, showing more details of the cloud-top morphology than the regular DNB image (Figure 1).
Figure 3: Black-and-white 11.45 microns band
This image shows a regular black-and-white displayed 11.45 microns (375 m) band.
The structure of the warm inner area (above the core of this volcanic cloud) shows up better in the inverted image (Figure 4), where the warm plume, which is brighter in this image, can be easily seen drifting westwards.
Figure 5: Colour-enhanced 11.45 microns band
The thermal structure of the whole cloud top is best revealed in this colour-enhanced 11.45 microns band image. The brightness temperature scale is inserted in this image — the blue end of the color enhancement represents temperatures around 230 K, while the red part shows the cloud tops at about 180 K, the minimum temperature detected for this cloud in 11.45 microns band.
Figure 6: Sandwich product
The image is the sandwich product of Figures 2 and 5, merging together the morphology of the cloud tops as seen in the DNB, together with thermal information from the 11.45 microns band.
The VIIRS SDR Level 1 data were retrieved from the NASA LAADS archive , processed in ENVI 5 software , using the VIIRS Conversion Toolkit (VCTK, version 1.0.6). Final processing of the images, HDR DNB product and the sandwich product were created in Photoshop CS5.
MODIS Dust RGB image
The RGB image taken about 1.5 hours after the Metop overpass. The ash plume is indicated by the yellowish colour.
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