Eruption of Calbuco Volcano, Chile

By Jochen Kerkmann, Mark Higgins, Vesa Nietosvaara and Michael Grzegorski (EUMETSAT) and HansPeter Roesli (Switzerland)

The Meteosat-10 Dust RGB shows the plume from the second eruption, as it headed towards Chile, Argentina and Uruguay at 05:00 UTC on 24 April.

The eruption caused air traffic disruptions with a number of international flights cancelled or delayed. Qantas flight QF27 was five hours into its journey to Santiago when it had to turn back to Sydney.

The Calbuco volcano in southern Chile erupted around 21:03 UTC on 22 April, as can be seen on the GOES-13 visible image from 21:38 UTC (Figure 2) and the infrared animation from 22 April 20:38 UTC to 23 April 13:38 UTC (Figure 3).

There was a second explosive eruption that began some time before the Suomi-NPP VIIRS image from 05:13 UTC (Figure 4). The I-band 5 (11.4µm) minimum brightness temperature within the overshooting top of the second plume was -101°C, which is extraordinary for mid-latitudes and indicates a cloud top height of well above 15km.

The volcanic cloud from the second eruption can also be seen in the VIIRS Ash RGB product (Figure 5) close to the position of the Calbuco volcano in the lower part of the image. The colour (brown) indicates a very thick ash cloud. The cloud from the first pulse is visible more to the north (red and yellow colours), stretching east-west along a deformation zone. The yellow colour indicates the presence of SO₂ inside the plume (probably together with the presence of small ash particles).

About one hour later, Aqua MODIS also captured the volcanic plumes (Figure 6). Note that no retrievals are present in the core of the cloud produced by the second explosion due to its large optical depth. The MODIS retrievals show small effective radii in the eastern, and highest portion, of the dispersed cloud (yellow colour in the Ash RGB product, top left) from the first eruption. The relatively small area of larger heights in the western portion of the dispersed cloud are likely an artifact of the unsupervised, near-real time retrieval process.

Unfortunately, the volcanic clouds were located near the edge of the Aqua MODIS morning pass, which means that a CALIPSO overpass above the cloud was not available (CALIPSO and Aqua fly in nearly the same orbit, offset by a few minutes). But the CALIPSO afternoon overpass captured the volcanic plume, the portion of the cloud overpassed by CALIOP was as high as about 17–18km (Figure 7).

A daytime view of the volcanic clouds was provided by Suomi-NPP VIIRS on 23 April at 19:10 UTC (Figures 8 and 9). At this time, the volcanic clouds stretch from the west to the east coast of southern South America.

In the Ash RGB product (Figure 9), most of the cloud, which is getting thinner as it moves away from the Calbuco volcano, is yellow (ash and SO₂ mixed), but there is also a larger red area ('pure' ash cloud) and a small cyan-green band close to Santiago ('pure' SO₂ cloud with some remaining ash particles).

The presence of SO₂ in the yellow and cyan parts of the volcanic cloud is confirmed by GOME-2 (Figure 10) and AIRS (Figure 11) SO₂ vertical column products.

Although right on the edge the Meteosat-10 field of view, the volcanic plumes could also be seen on Ash and Airmass RGB imagery (Figures 12 and 13).

The Airmass RGB (Figure 13) is sensitive to high-level sulphur dioxide, because of the WV7.3 band that is used in combination with the WV6.2 in the red component of the RGB. The Ash RGB (Figure 12) is sensitive to both SO₂ and ash clouds.

The animations above follow the plume of the Calbuco eruptions across the South Atlantic from 23 to 27 April. The Airmass RGB animation shows the high-level SO₂ plume (bright red, gradually fading), as it crosses Argentina, Paraguay, Uruguay and Brazil (it reaches Buenos Aires at around 10:00 UTC on 24 April). In the second part of the animation, when the plume crosses the Atlantic and gets thinner, the colour of the SO₂ plume gets 'weaker' (more orange), thus it is more difficult to distinguish it from regions with low upper-level humidity (also orange colour).

The Ash RGB animation shows both the ash (pink to magenta), SO₂ (cyan-green) and ash mixed with SO₂ (yellow). On its way to the mid Atlantic, the colour turns from mainly yellow to mainly cyan-green, hinting that the ash is falling down, leaving, essentially, only SO₂ behind.

The Polar Multi-Sensor aerosol product retrieves aerosol optical depth over sea (Figure 14) and a volcanic ash classification flag (Figure 15, ash pixels marked in red) using GOME and AVHRR on Metop. The transport of the ash over sea can be clearly observed in both products.

The PMAp results are also in a very good agreement with the SO₂ observations from GOME showing a strong plume moving eastwards. The operational sulphur dioxide products from GOME-2 Metop-A and -B are produced by the O3M SAF.

Additional content

Gravity Waves Associated with Calbuco Volcanic Eruption (CIMSS Blog)
Calbuco Volcano Erupts in Southern Chile (NOAA)
Tracking the Sulfur Dioxide from Calbuco (NASA Earth Observatory)
Time lapse video of the eruption (Rodrigo Barrera/YouTube)
Chile volcano Calbuco causes flight problems (BBC News)