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CAMS Forecast of total column of Sulphur Dioxide for initialized at 00 UTC on 19 October and valid for 12 UTC. CAMS forecasts are based on satellite observations of SO₂ total columns (i.e. the number of SO2 molecules per unit area in a column from the surface to the top of the atmosphere). Credit: Copernicus Atmosphere Monitoring Service/ECMWF

As part of their continuous work on atmospheric composition and air quality around the world, scientists from the Copernicus Atmosphere Monitoring Service are closely monitoring after-effects of the Cumbre Vieja volcano eruption on La Palma in the Canary Islands which has caused large plumes of sulphur dioxide to travel over North Africa, Europe as well as across the Atlantic to the Caribbean

Scientists at the Copernicus Atmosphere Monitoring Service (CAMS) have been closely monitoring the impact of La Palma’s Cumbre Vieja volcano on atmospheric composition since it first erupted on 19^th September 2021, including the long-range transport of large plumes of sulphur dioxide (SO₂) over thousands of kilometers. The volcano, on the Spanish island of La Palma in the Canary Islands, erupted for the first time in 50 years, causing widespread destruction from its multiple lava flows and shows little sign of abating after nearly a month.

CAMS, which is implemented by the European Centre for Medium-Range Weather Forecasts on behalf of the European Commission with funding from the EU, consistently monitors air quality across the globe, providing users with data on past atmospheric composition and forecasts for the next few days. Using data from satellite observations, CAMS can assess many aspects of global air quality, including the impact of natural phenomena such as volcanic eruptions, wildfires and desert dust. The combination of observational data with a detailed model of the Earth’s atmosphere allows CAMS to predict atmospheric composition up to 5 days in advance. Since the Cumbre Vieja volcano first erupted in September, CAMS scientists have monitored the transport and chemical evolution of SO₂ emitted by the volcano as it has been transported across North Africa, Europe and the Atlantic. While the forecasts can show SO₂ in the atmosphere, CAMS does not use or provide information on volcanic ash, which is the responsibility of the Volcanic Ash Advisory Centres (VAACs).

When the Cumbre Vieja volcano first erupted on September 19^th, 2021, the plumes travelled mainly across northern Africa and southern European countries including Spain and Portugal, eventually reaching northern and western Europe.

CAMS analysis of Saharan dust which coincided with the arrival of SO2 plumes in the Caribbean as of 9^th October. (Credit: Copernicus Atmosphere Monitoring Service/ECMWF)

However, in early October, the wind direction changed, and CAMS tracked SO₂ plumes being transported over an approximate distance of 5,000 kilometres reaching the Caribbean. In addition to SO₂, CAMS provides information on particulate matter in the atmosphere, both in terms of the concentration and in Aerosol Optical Depth (AOD). Chemical conversion of SO₂ into sulphate aerosol is included in the CAMS model and CAMS analyses of AOD for this period revealed a transport of sulphate aerosol in conjunction with total column SO₂. Transport of Saharan dust across the Atlantic coincident with the volcanic plume resulted in reports of haze and poor air quality in Puerto Rico and other parts of the Caribbean between 8^th and 10^th October with visibility being down to five miles or less. Evaluation of CAMS forecasts for concentrations of fine particulate matter (PM2.5) showed increased values at some sites in Puerto Rico, corresponding with in-situ measurements.

Mark Parrington, Senior Scientist at the ECMWF Copernicus Atmosphere Monitoring Service, comments: “The Cumbre Vieja volcano has been erupting consistently for over a month now with wide-reaching impacts on atmospheric composition, as well as the local devastation caused by the lava flow. In CAMS, we monitor air quality around the world to provide information to better understand the effects of naturally occurring events such as this at different scales. Our monitoring of this event depends on the availability of satellite observations of SO₂ and we assume an initial injection at approximately 5 km altitude which, in this case, seems to be reasonable in capturing the long-range transport of the plume across Europe and as far as the Caribbean. When the SO₂ plume is at this height, as seen originally over Europe, the risk to air quality reduction is very small. However, as we tracked the plume 5,000 km towards the Caribbean, we observed the drop in air quality related to the conversion of SO₂ into sulphate aerosol, which also corresponded with the arrival of Saharan dust.”

“While the eruption of a volcano is a natural phenomenon, it is vital that we monitor the height, transport and transport of sulphur dioxide plumes to understand any potential impacts on air quality downwind of the volcano.” he adds.

The sulphur dioxide plumes are predicted by CAMS daily forecasts to recirculate to northern and western Europe by mid-October. Scientists will continue to monitor the plumes and air quality of affected regions for as long as the volcano continues to be active.

CAMS total column sulphur dioxide forecasts can be seen here:

https://atmosphere.copernicus.eu/charts/cams/sulphur-dioxide-forecasts?facets=undefined&time=2021092100,57,2021092309&projection=classical_south_west_europe&layer_name=composition_so2_totalcolumn

CAMS sulphur dioxide forecasts at the surface can be seen here:

https://atmosphere.copernicus.eu/charts/cams/sulphur-dioxide-forecasts?facets=undefined&time=2021092100,57,2021092309&projection=classical_south_west_europe&layer_name=composition_so2_surface

A visualization using the Windy.com-App of the predicted transport of sulphur dioxide from the Cumbre Vieja volcano, can be found here: https://twitter.com/m_parrington/status/1448267884065591302?s=20

More information on challenges in modelling volcanic eruptions: https://atmosphere.copernicus.eu/solving-challenges-modelling-volcanic-eruptions

More information on the eruption of Cumbre Vieja: https://atmosphere.copernicus.eu/cams-monitors-transport-so2-la-palma-volcano-nf

As part of its monitoring role and as an important international actor to understand and analyse air quality, CAMS has recently participated in updating WHO´s global air quality guidelines. The report can be downloaded here: https://www.who.int/publications/i/item/9789240034228.