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EUMETSAT’s geostationary Second Generation Meteosats are the only satellites in orbit that can be used to derive real-time high-frequency imagery of the movement of volcanic dust clouds over Europe. The animation 1 shows Meteosat-9 observations from the High Resolution Visible (HRV) channel, providing measurements with a resolution of 1 km at the sub-satellite point, representing roughly a 3-5 km resolution over Iceland.  At around 19:15 UTC, a very rapid eruption of the Grímsvötn volcano occurred, which is visible from the animation below. The eruption is transporting a large amount of water vapour and ash significantly higher than the cloud deck heights over Iceland.

Animation 1: Meteosat-9 observations of the Grímsvötn eruption at around 19:15 UTC from the High Resolution Visible (HRV) channels. The data is produced by the EUMETSAT Central Application Facility (CAF).

Various instruments on board the Metop-A polar-orbiting satellite can also be used to derive the track of the Grímsvötn volcanic plume in different ways.  The data from the GOME-2 (Global Ozone Monitoring Experiment-2) can be used to detect the broad-band absorption of ultraviolet radiation by the volcanic ash from which the Absorbing Aerosol Index (AAI) product can be derived. Sulphur dioxide (SO2) can be measured from the same instrument using the specific absorption features of this gas in the ultraviolet spectral region.

The high-resolution Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A is sensitive to both SO2 and ash aerosol, and their concentrations are derived from the variations observed in the measured infrared radiation, derived as brightness temperature levels.

Finally, volcanic plumes can be monitored at very high spatial resolution by constructing red-green-blue (RGB) images from the Advanced Very High Resolution Radiometer (AVHRR) on board Metop. All methods show the volcanic plume during Metop overpasses, once (or twice) per day, here at around 13:50 UTC.

Figure 1 shows the SO2 plume as derived from GOME-2 on 22 May 2011 at around 13:50 UTC. The quantities of SO2 emitted during this current eruption are significantly larger than those measured during the eruption of the Eyjafjallajökull volcano in April 2010 and larger than the eruption of Grímsvötn in 2004. The product is produced by the Ozone Monitoring Satellite Application Facility (O3MSAF), and provided through the Support for Aviation Control Service (SACS) website by BIRA-IASB.

Figure 2 shows SO2 as derived from IASI during the day (13:50 UTC), also indicating the large SO2 concentrations associated with this eruption. The product is produced by ULB/BIRA-IASB and provided through the Support for Aviation Control Service (SACS) website by BIRA-IASB.

Figure 3: At the same time, GOME-2 is observing an eruption of volcanic ash. The plot shows the AAI derived from the ultra-violet part of the spectrum measured by GOME-2. The product is produced by the O3MSAF and is available from the Support for Volcano Ash Advisory Centres (VAAC) website, hosted by ESA.

There are first indications that the SO2 and ash injections are reaching very high altitudes (significantly above 10 km) and therefore reaching the stratosphere, which will mean that the resident time and the distribution of both ash and SO2 can potentially be long and widespread. The volcanic ash plume is drifting south-eastwards of the island, whereas the SO2 plume is initially drifting north-east. This is indicative for different injection heights of both plumes.

Figure 4 shows the very high spatial resolution RGB image from AVHRR. The volcanic ash plume is drifting more south-eastwards of the island. Near-real-time imagery from AVHRR is available on the EUMETSAT website.

Animation 1: High Resolution Visible (HRV) channels. (Click to enlarge)

Figure 1: SO2 concentration in Dobson Units. (Click to enlarge)

Figure 2: SO2 brightness temperature index. (Click to enlarge)

Figure 3: AAI as derived from GOME-2. (Click to enlarge)

Figure 4: RGB composite image. (Click to enlarge)

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