Volcanic eruptions in Pacific Ocean region

By Federico Fierli, Sancha Lancaster, HansPeter Roesli, Anu-Maija Sundström, Sabrina Szeto, Julia Wagemann

Table of contents

2022

Mauna Loa

28 Nov-1 Dec, Hawaii
By Federico Fierli, Anu-Maija Sundström, Sabrina Szeto, and Julia Wagemann

Mauna Loa is the world’s largest active volcano, and it is located on the south-central part of Hawaii’s Big Island. On 27 November, the volcano began erupting for the first time since 1984.

In volcanic eruptions, large amounts of gases, ash, and other aerosol particles are emitted in the atmosphere. One of the major emitted species is sulfur dioxide (SO₂), which is a reactive gas and an important indicator of volcanic activity.

SO₂ emissions from volcanic eruptions are clearly visible from satellite observations. One of the first satellite observations of the Mauna Loa SO₂ plume was captured by the Global Ozone Monitoring Experiment-2 instrument (GOME-2) onboard the Metop-B and Metop-C satellites on 28 November (Figure 1).

The plume of SO₂ with more than 10DU was emitted to the troposphere with an estimated plume height of about 6km in the immediate vicinity of the volcano (Figure 2).

The SO₂ plume was transported eastwards over the United States, then the Atlantic, up to the west coast of Africa, reaching plume heights of about 8-15km. Overall, SO₂ emissions were being transported more than 12,000km from their origin.

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.

Figure 3 shows GOME-2 observations on 3 December, when elevated SO₂ concentrations from Mauna Loa, were visible being transported to the west coast of Africa.

Figure 4 shows emissions on 7 December, when the direction of the transport changed more towards the north. The plume remained visible in satellite observations until 12 December.

Additional content

Hawaiian Volcano Observatory updates
CAMS

2019

Raikoke

21 June-5 July, Kuril Islands
By Sancha Lancaster, Hans-Peter Roesli, and Anu-Maija Sundström (FMI/AC SAF)

A powerful, rare eruption from Raikoke volcano in the Kuril Islands on 21 June 2019, could be clearly seen on satellite imagery.

On 21 June, just before 18:00 UTC, volcano Raikoke in the Kuril Islands, started a sequence of spectacular eruptions. It is reported that the last big eruptions dated from 1924.

Himawari-8 detected the first signs at local daybreak, between 17:50 UTC and 18:00 UTC. Both, the Himawari-8 visible band VIS0.64 and the Volcanic Ash RGB captured the first emerging plume of SO₂ and ash from the eruption (Figure 5).

The red arrows on the top left panel (VIS0.64 at 17:50 UTC, 500m spatial resolution at subsatellite point (SSP), enhanced) point to the very feeble shadow of the emerging plume. Ten minutes later shadow and plume were evident (top right panel).

On the Volcanic Ash RGB (lower left panel, four times lower spatial resolution than the VIS0.64) a red arrow points to a dark spot, which turns into a rising plume of SO₂ (green pixel) and ash (brown pixels) ten minutes later.

All four panels are in native projection in order to get a 3D-impression. Checking band IR3.9 for a hot spot (not shown) did not reveal any sign either before or after the first eruption, probably due to an inadequate spatial resolution or the oblique view not reaching the hot lava sources.

Also in native projection the animation of the same image couple (Figure 6) documents the evolution of the eruptions during the local daytime of 21 June (21 June 18:00 UTC to 22 June 09:00 UTC).

During this initial phase of the volcanic activity a sequence of large eruptions spewed considerable amounts of ash and SO₂ into the atmosphere, that spread, at low level westward, then, after reaching 5km height, eastward, accompanied by some overshooting tops consisting of ash (red tints) and sometimes mixed with SO₂ (yellow).

At the same time, although at a slower pace, ash moved in the opposite direction. This outflow appears to be confined to lower levels, as confirmed by the GFS analysis of the wind cross section from Raikoke on 21 June 18:00 UTC, see red barbs in wind cross section on Figure 7. Close to Raikoke the winds in the maritime boundary layer, ie up to some 2–3km, were rather weak and from the east, whereas from 3km to 16km stronger westerlies were blowing from Raikoke, beyond a distance of 800km.

The animation in polar-stereographic projection of Volcanic Ash and Airmass RGBs, from the start of the eruption to its end at about 16:00 UTC on 23 June (Figure 8), not only shows the very clear ash and SO₂ signals in the Volcanic Ash RGBs (red, yellow and green) on the left panel, but also an extraordinary SO₂ signal in the Airmass RGB (red) in the right panel.

The deep red colour suggests that the standard temperature range of the WV6.2–WV7.3 difference, which colours the red beam, was saturated due to a large amount of SO₂ under a slant viewing angle, reducing brightness temperature at 7.3µm through an intense absorption line.

The position of the tropopause and lower stratosphere can be gathered around 150hPa from the skew-T profile extracted from the GFS analysis at 18:00 UTC on 21 June (Figure 9).

Therefore, it is assumed that most of the long-distance SO₂ transport happened in the westerly winds in the drier higher troposphere and lower stratosphere up to around 16km high.

After having travelled eastward for a few hours and shedding most of the ash, the high-level SO₂ swath was taken up by a big deep cyclonic whirl over the Aleutian.

Figure 10 shows the situation at 09:00 UTC on 23 June, again in the Volcanic Ash and Airmass RGBs, when the cyclonic path had already made much progress. At the same time, a first break-up of the streamer, due to a deformation zone, had set in (white arrows). Subsequently, above Siberia, the SO₂ streamers broke down into ever smaller whirls and streaks. The SO₂ distribution became quite chaotic, it even flowed back over the Kuril Islands.

The GOME-2 instruments on Metop-A and B also detected the large sulphur dioxide plume. The AC SAF SO₂ products (Figure 11 and 12) show the very small expulsion of SO₂ on 21 June and the swirling mass of SO₂ by 27 June.

The combined view from Himawari-8 and GOES-E (GOES-17) gives an idea of the situation on 28 June at 00:00 UTC (Figure 13).

The SO₂ was still detectable on the Himawari-8 RGBs for a few days beyond that date. The animation in native projections of hourly Volcanic Ash and Airmass RGBs gives an overview from the start of the eruption on 21 June to 5 July (Figure 14).

Note: In other volcanic eruptions that were documented with Airmass RGBs, this RGB never showed such a strong (deep red) SO₂ signal. Compared to this event, these cases (see Previous Case Studies below) were observed at smaller viewing angles and in a very dry upper troposphere. In this case of Raikoke the airmass was variably humid through almost the whole troposphere, as shown by the blue to green colouring in Figure 3 and only really dry (yellow) only from close to the top of the troposphere upward.

Additional content

Eruption of the Raikoke volcano in the Kuril Islands (CIMSS Blog)
Raikoke Volcano's Eruption Seen from Space (Photos) (Space.com)
Raikoke Erupts (NASA Earth Observatory)
Volcano Raikoke spits ash over Bering Sea (Phys Org)
Raikoke volcano news & activity updates (Volcano Discovery)

2018

Aoba

5-14 April, Vanuatu
By HansPeter Roesli

The activity between 5 and 14 April can be seen in the Himawari-8 animation using Volcanic Ash RGBs from AHI at 10-minute intervals (Figure 15). The animation shows two major eruptions with a pause (shown in fast-forward) between 6 April 06:00 UTC and 9 April 16:20 UTC. Coincidentally, during the lull the area was frequently shrouded in convective cloud.

On 15 April the Wellington VAAC office reported that the eruption had ceased. The different phases of the eruptions are commented on in more detail below.

SO₂ plume travelling to the Coral Sea

A map of SO₂ concentration extracted from IASI on Metop, tweeted by Simon Proud (@simon_sat), showed a patch of high values east of Australia. The map was from 10 April and the tweet hinted that the SO₂ was being ejected from the volcano Aoba.

In fact, the first part of the animation in Figure 17 shows an eruption on 5 April after 13:50 UTC, with an SO₂ plume (green colour) that morphed into a ring while travelling west (see Figure 16).

According to the Ash and SO₂ RGB sequence (Figure 18) the SO₂ passed north of New Caledonia and arrived over the Coral Sea 24 hours later, very close to where IASI detected the large SO₂ patch.

The peculiar ring-shape of the SO₂ plume may be explained by the closest radio-soundings at Nouméa in New Caledonia (540km south-west of Aoba) on 5 April 12:00 UTC and 6 April 00:00 UTC. They show a temperature inversion at/above 700hPa and moderate easterly winds below.

Most probably, the plume has evolved under this temperature inversion in a rather laminar flow that favoured its regular horizontal expansion.

SO₂ and ash going east

After the lull, from 9 to 14 April, the skies cleared up somewhat and the renewed eruptions reached greater heights than before, most of them ending up in the westerly regime above the boundary layer.

The left-hand panel of Figure 18 shows a plume where the ejection of mainly ash (pink to grey colour) alternated with one of mainly SO₂ (green colour). In contrast, one day later (right-hand panel) an almost pure SO₂ plume encountered a turbulent regime and meandered considerably.

Going west again

After 11 April the eruptions weakened and the effluents were again driven westwards by the winds in the boundary layer. Sentinel-3A’s OLCI instrument scanned the area in daylight on 12 April.

The True Colour RGB from 12 April 22:20 UTC (Figure 19, left panel) shows a northwest pointing plume. Strangely enough, on the Himawari-8 Volcanic Ash RGB from the same time (Figure 19, right panel) the streak is hardly recognisable — very weak SO₂ colouring but no ash colours.

Mount Mayon

14-24 Jan, Philippines
By HansPeter Roesli

On 14 January Mount Mayon, the Philippines' most active volcano, started to erupt. This continued for at least two weeks and could be seen on both Himawari-8 and Suomi-NPP imagery between 22 and 24 January.

Figure 21 shows an animation of the Ash RGB from Himawari-8's AHI instrument, from 22 January 00:00 UTC to 24 January 06:00 UTC, the location of the volcano is indicated by a red dot.

The sequence shows a series of short eruptions seemingly consisting almost exclusively of ash (dirty red to dark violet) — no sulfur dioxide (SO₂) (light green) appears to be present. It ends at 06:00 UTC on 24 January, after a couple of hours without discernible activity on the images, as Mount Mayon ends up under cloud cover.

The Suomi-NPP Natural Colour RGB at 375m spatial resolution, from 05:20 UTC on 22 January (Figures 20 & 22), shows a meandering ash plume (brown arrows pointing to middle-grey plume) moving towards the north west, and varying between weaker to denser ash streaks.

There are another two dark patches near the volcano that do not stem from ash. On Figure 22 (the annotated version of the same image) the patch indicated by a blue arrow is a lake. The other, shown by the magenta-coloured arrow, is the shadow cast by the cyan-coloured ice cloud that fans out from the volcano, which signals a new, relatively strong eruption, that can be followed in the Himawari animation.

Additional content

Philippines volcano: lava erupts from Mount Mayon as ash covers towns (The Guardian)
The Philippines' most active volcano Mount Mayon erupts (BBC News)

2017

Aoba

22 Sep-1 Oct, Vanuatu
By HansPeter Roesli

Volcano Aoba, or Ambae, in the South Pacific nation of Vanuatu, had intermittent eruptions in September and October 2017.

The imaging radiometer AHI on Himawari-8 covered this period with imagery in 16 radiometric bands at 10-minute intervals.

The eruptive plumes did not reach great heights, so passing cloud decks hid or mixed with the volcanic effluents. Nevertheless, the Volcanic Ash & SO₂ RGB identified a couple of cyan-coloured SO₂ swaths between 22 and 23 September, as shown in the image sequence from 22 September 17:00 UTC to 23 September 23:00 UTC.

However, the ash signal did not show up very clearly in these RGBs. While the display of various shades from a dirty red to dark blue (instead of the typical pink) hinted at the presence of ash or other effluents, it manifested rather by its dynamical behaviour, ie by plumes originating from the crater area.

The single frames in Figure 23, 23 September 00:50 UTC (left slider) and 23 September 04:30 UTC (right slider) show examples, where the latter frame also offers a glimpse of the hot spot.

Image comparison

23 Sept 00:50 UTC 23 Sept 04:30 UTC

 

Reflected sunlight in the high resolution band VIS0.64 (spatial resolution of 0.5km v 2km in the infrared bands used to construct the Ash & SO₂ RGB) gave some more details of the various plumes and streamers. The image sequence from 22 September 19:00 UTC–25 September 06:30 UTC is three consecutive days The sequence shows many differently shaped outbursts during the daylight hours.

A couple of individual frames and their Ash & SO₂ RGB counterparts may help to identify some of those in the animation.

Figure 24 is the visible imagery showing a short initial outburst early on 22 September (locally the 23 September), that in the Ash & SO₂ RGB appeared as a faint SO₂ colour.

A little over six hours later Figure 25 shows a much stronger outburst. The VIS0.64 indicates a pulsating plume that originated from a tiny dark-grey spot, the active crater of Aoba. Due to the reduced resolution, the Ash & SO₂ RGB did not show the knotty pattern, but illustrated the crater as a hot spot in dark blue.

On 23 September at 21:30 UTC (24 September locally) (Figure 26) the visible imagery showed a southward-pointing plume that mixed with the cloud deck moving through the scene. In the Ash & SO₂ RGB that plume was hardly visible.

One hour later, the plume was still there, and the True Colour RGB from Sentinel-3’s OLCI imaging radiometer showed the situation in more detail.

Three hours later the scene took on a more chaotic look. On Figure 28, an image couple from Himawari-8 is compared to a Natural Color RGB and an Ash & SO₂ RGB from the VIIRS imager on Suomi NPP at 375m and 750m spatial resolution, respectively. Note the active crater on the VIIRS images (upper row), a tiny red spot in the Natural Colour RGB and a blue blotch on the Ash & SO₂ RGB. On the Natural Colour RGB the crater was surrounded by dark colours, hinting at deposited ash.

Aoba maintained some activity after 26 September — the animated visible imagery from 1 October, 19:00–21:00 UTC (Figure 29) showed a weak plume moving westward in the two hours after sunrise.

2014

Mount Ontake

27 Sep, Japan
By HansPeter Roesli

Mount Ontake, Japan's second highest volcano, erupted shortly before noon on 27 September, sending thick plumes of ash and rocks into the air.

Ash up to 20 inches deep covered large swathes of the mountain after the volcano erupted. A major rescue effort took place to bring down hikers who had been climbing the mountain. More than 30 people were believed to have died.

Full Resolution Suomi-NPP Volcanic Ash and SO₂ RGB

The zoomed split-window differences images above, taken a few hours after the eruption and almost 50 minutes apart, show a considerable weakening of the ash output — yellow pixels indicating negative differences of IR10.8-IR12.0 the ash signal.

However, this observation is only possible with hindsight after looking at Suomi-NPP VIIRS images. On the image comparison below the Natural Colour RGB image shows a small grey plume pointing eastward. The Volcanic Ash and SO₂ RGB is much clearer, with pink areas indicating ash and light-green areas indicating SO₂ (clouds appear as orange).

Image comparison

Natural Color RGB Volcanic Ash and SO2 RGB

 

Additional content

Five more bodies found on Japan's Mount Ontake after eruption (CNN)
Ash cloud captured by the Modis Satellite (Robert Speta/Twitter)
Volcanic Cloud Monitoring (NOAA/CIMSS)

2008

Kasatochi

7-31 Aug, Aleutian Islands
By HansPeter Roesli

Sulphur dioxide (SO2) plumes from the Kasatochi eruption circled the whole northern hemisphere over more than 20 days

Kasatochi is a small island volcano located in the Aleutian Island chain just east of 180° longitude (see map ). According to the Alaska Volcano Observatory of the USGS, on 7 August 2008: "Satellite data show an ash plume to an altitude of at least 35,000 feet in the vicinity of Kasatochi Volcano 22:30 UTC (14:30 ADT). The plume is drifting to the south-southwest."

Courtesy of the same website an animated sequence of GOES-12 images (Credit: David Schneider) depicts the expanding ash cloud resulting from the eruption. More information on the Kasatochi volcano may be found at the Smithsonian's Global Volcanism Program.

The SO₂ plumes trajectories have also been observed in the so-called Ash RGB composites of Meteosat-9, and with the GOME-2 and IASI instruments on Metop-A.

Both the amount of backscattered UV radiation from the Sun (GOME-2) and the emitted IR radiation (SEVIRI, IASI) are sensitive to the presence of SO₂. The hemispheric SO₂ circulation is well depicted by an animated sequence of the GOME-2 SO₂ product (daily composites, Credit: Univ. of Bremen). Limited to Meteosat-9's field-of-view, the Meteosat-9 Ash RGB sequence offers a smoother view of the trajectories of some of the light-green coloured SO₂ streaks.

Arrows on four RGB frames (16 August, 17 August, 20 August, 21 August ) allow better tracking of the SO₂ in the image loop.

The situation on 21 August offers a good opportunity to compare the RGB with the SO₂ product from GOME-2 and a simple SO₂ scheme from IASI. A narrow SO₂ streak over the eastern Atlantic moves slowly south-southeastwards crossing the British Isles and the Gulf of Biscay (see hourly Meteosat-9 Ash RGB sequence). A shorter RGB sequence (21 August, 08:00–14:00 UTC) overlaid with the GOME-2 product of the morning orbit matches reasonably well when taking into account the different observation techniques used and the considerable mismatch in spatial resolution.

IASI data are only available for the evening orbit. A simple qualitative scheme, namely the temperature difference on/off an SO₂ absorption line (1284cm^-1 minus 1344cm^-1) and free of other trace gas absorption, is used to show the presence of SO₂. There is an excellent match of the signals (left frame) between the light-green RGB streak (middle frame) and the dark IASI streak (right frame).

Compared to the Chaitén eruption in May 2008, where the volcanic SO₂ clouds followed the flow of smooth planetary waves around the southern hemisphere, Kasatochi's SO₂ streaks trace a more wave-like upper tropospheric flow over the northern hemisphere — as one would expect.

Animated sequence (10–20 August 2008)
(Credit: DLR, Applied Remote Sensing Cluster)
Animated sequence (01–31 August 2008, animated )
(Credit: A. Richter & colleagues, Univ. of Bremen)

Additional content

Met-8 24-h Cloud Microphysics RGB animation (5-minute scan interval) (21 Aug 12:00 UTC–22 Aug 06 UTC)