Features

Volcanic activity during the course of the following day (22 May) in central Iceland was observed via the High Resolution Visible (HRV) channel of EUMETSAT’s geostationary Second Generation Meteosat satellites (MSG) at the three to five kilometre resolution (Animation 1). See also an earlier animation from yesterday's report.

Volcanic ejecta are seen to follow different routes, possibly due to different injection heights of the SO2 and the volcanic ash plume. Shortly after the eruption the majority of the SO2 drifted northward, whereas the volcanic ash quickly dispersed. In addition, a significant fraction of the emitted volcanic ash has been transported southwards. Animation 2 shows the Grímsvötn volcanic ash cloud drifting south east, as observed by MSG. Clouds contaminated with volcanic ash are highlighted by the pink hues in order to separate them from non-contaminated cloud decks.

SO2 plume spreading out in the polar regions

The high-resolution Infrared Atmospheric Sounding Interferometer (IASI) on EUMETSAT’s Metop-A polar-orbiting satellite observed the SO2 as it spread out during the last couple of days over Greenland, the polar regions and towards Siberia. Some of the SO2 has reached the stratosphere, leading to relatively long persistence at higher altitudes. The large area covered by the plume can be seen in Animation 3. SO2 observations with the IASI instrument are defined by the variation of IASI brightness temperature measurements due to elevated SO2 concentrations in the atmosphere.

Volcanic ash travelling south-east towards Europe

While a large part of the SO2 plume is distributed over the polar regions, a significant faction of the volcanic ash plume emitted by Grímsvötn is travelling towards the south east toward Europe. The ash cloud is followed by the MSG Volcanic Ash Index, derived from satellite imagery using a dedicated algorithm developed by EUMETSAT’s NWC SAF (Animation 4). By the morning of 25 May the intensity of the ash cloud - reaching the south of Norway in the meantime - has decreased below the detection limit.

Data from the GOME-2 (Global Ozone Monitoring Experiment-2) instrument on board Metop-A can also be used to detect the broad-band absorption of ultraviolet radiation by the volcanic ash, which forms the basis of the Absorbing Aerosol Index (AAI) product. Animation 5 shows the AAI from GOME-2 which is available around mid day, when Metop-A passes over Europe. The AAI product as shown here is produced as an experimental product by Tuinder et al at the KNMI, in support of EUMETSAT’s O3MSAF. Related imagery from GOME-2 is also available from the TEMIS website hosted by ESA, in support of the Volcano Ash Advisory Centres (VAAC).

Figure 1 shows the same ash cloud as observed by the IASI instrument on 24 May 11:35 UTC. IASI, as well as the other instruments on Metop-A, typically observes the region of the ash cloud twice every 24 hours - once in the morning and again at night.

 A volcanic ash index is derived from variations observed in the infrared brightness temperatures measured by the instrument. The product is provided by ULB and LATMOS.

In correspondence with the volcanic ash index derived from the geostationary satellite (MSG), the ash cloud as observed by the polar orbiting instruments (GOME-2 and IASI) reached the North Sea by 23 May and presently travelling eastwards, reaching the south of Norway on 25 May at significantly decreased concentration levels.

The flight trajectory monitoring provided by flightradar24.com shows a consistent picture, with the majority of flights avoiding the affected region on 24 May, at around 12:00 UTC over the North Sea - as shown in Figure 2.

Animation 1: High Resolution Visible (HRV) channel of EUMETSAT’s geostationary Second Generation Meteosats (MSG) (Right click to save and view animation - AVI, 2.2 MB)

Animation 2: Grimsvotn volcanic ash cloud drifting south-east as observed by MSG. (Right click to save and view animation - MPG, 9.5 MB)

Animation 3: SO2 concentrations derived from IASI, spreading out over the Polar Regions. (Click to enlarge) 

Animation 4: Volcanic Ash Index derived from MSG imagery using an algorithm provided by EUMETSAT’s NWC SAF. (Click to enlarge)

Animation 5: AAI as derived from the GOME-2 instrument on board Metop-A. (Click to enlarge)

Figure 1: Volcanic Ash Index on 24 May 11;35 UTC, as derived from IASI brightness temperature measurements onboard Metop-A. (Click to enlarge)

Figure 2: Flight positions at 12:00 UTC as provided by flightradar24.com correlated with a Metop-A overpass and the detection of the ash cloud by the GOME-2 instrument. (Click to enlarge)

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