Providing information on sulphur dioxide from the Cumbre Vieja eruption to aviation.

For the first time since 1971, the Cumbre Vieja volcano on La Palma (Canary Islands, Spain) started to erupt on 19 September 2021 at 13:10 UTC, more than a month ago. Together with the outflowing lava, the volcano emits ash and several gases, amongst these sulphur dioxide (SO₂). Volcanic ash and SO₂ are dangerous to public health and aviation (damage to engine due to ash melting and sulphidation). Therefore, tracking and monitoring volcanic plumes and their constituents is very important. For this reason, since 2009 the Support to Aviation Control Service (SACS; https://sacs.aeronomie.be) system uses satellite observations from UV-vis and IR hyperspectral sensors to detect ash and SO₂ emissions. For this particular eruption, no ash notification has currently been sent by SACS. However, since the start of the eruption, daily notifications of exceptional SO₂ concentrations have been sent to users by the SACS system. Dedicated webpages are created with key information and links to tailored images (e.g., alert and Google Earth) and data (e.g., https://sacs.aeronomie.be/TROPOMIalert/2021/09/alertsTROPOMI_20210920_14h12_205.php). In particular, the alert data file available through the SACS notifications are referred as NCAP, for NetCDF Alert Products (see details in Brenot et al. 2014, 2021).

A key source of information in the context of the Cumbre Vieja eruption comes from the Tropospheric Ozone Monitoring Instrument (TROPOMI) onboard the Copernicus Sentinel-5P satellite. TROPOMI provides observations at an unprecedented 3.5 × 5.5 km² spatial resolution and BIRA-IASB is in charge of the algorithm development to retrieve SO₂ columns from TROPOMI (Theys et al., 2017, 2019). SACS/ALARM EWS observes SO₂ with other sensors, such as the Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellites and the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the geosynchronous Meteosat Second generation satellites.

The transport of the SO₂ plume as observed by TROPOMI and SEVIRI instruments over northern Africa, southern Europe and the Atlantic Ocean from the 19^th of September to the 20^th of October 2021, is shown in the animation below. The right panel shows the RGB Ash composite product from EUMETSAT. This product has a high temporal resolution and allows to follow and nowcast the transport of the plume. However, the SO₂ detection from this broadband instrument is limited, as can be seen when comparing to the daily observations of TROPOMI SO₂ vertical column density (left panel).

The animation shows that the emitted SO₂ has been transported from the surroundings of the Canary Islands to the North of Africa (e.g., on 27 Sept. and 9 Oct.), to the South of Europe (e.g., on 25-26 Sept. and 19-20 Oct.), and along the Atlantic Ocean (e.g., on 30 Sept. and 6 Oct.). From the 19^th October onwards the plume was transported towards Portugal, Spain, France, UK and the Benelux. The observations on 20 October show a horizontal very thin plume of few hundred kilometers wide (an atmospheric river) which brings SO₂ towards Germany, Switzerland, Italy and Poland. This animation shows the added value of combining complementary observations from different satellite platforms, using different spectral information and different temporal resolutions.

For the time being, it is plausible that the eruption will continue for several weeks or even months. The volcanic emissions of Cumbre Vieja have not stopped since one month with ~50 kt of SO₂ emitted per day (inset figure of left panel) and a total of ~1.5 Tg.

Acknowledgements: We thank Pierre de Buyl and Nicolas Clerbaux from the Royal Meteorological Institute of Belgium (IRM-KMI) for providing near real-time access to SEVIRI data used in the frame of ALARM H2020 project (www.alarm-project.eu). We are currently working on the development and the implementation in SACS of selective detection of SO₂ and aerosols (Ash and dust) from SEVIRI.

Read also:

https://terrascope.be/en/news-events/monitoring-volcano-ash-plumes-la-palma-different-satellites

Contact:     Hugues.Brenot@aeronomie.be     and   Nicolas.Theys@aeronomie.be

References:

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Theys, N., Hedelt, P., De Smedt, I. et al. Global monitoring of volcanic SO2 degassing with unprecedented resolution from TROPOMI onboard Sentinel-5 Precursor. Sci Rep 9, 2643 (2019).

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