Satellite image of the month

February 2021 - Etna eruption

23 February 2021

Mount Etna is one of the most active volcanoes in the world. Eruptive episodes happen extremely frequently resulting in the ejection of lava, volcanic ash and SO2 into the atmosphere. On February 16th a series of eruptive episodes began which resulted in significant amounts of SO2 being emitted in separate events over a succession of days (ongoing at the time of writing). Sulphur dioxide is a toxic gas, and concern is rising about its impact on aircraft occupants. Within the framework of the International Civil Aviation Organization, the Met Office has been invited to trial a global SO2 forecasting capability.

Here we have 3 images displaying the SO2 plume from the 23rd February. The first two images are from the SEVIRI instrument on MSG, which as a geostationary satellite is able to capture the plume every 15 minutes. The images chosen are the Dust RGB, which has IR channels chosen to highlight desert dust, but is also useful for identifying volcanic ash and SO2. In this example ash shows up as a pink area to the north-west of Sicily and SO2 in a green colour between Sicily and Sardinia. The second image utilises the absorption of SO2 in the SEVIRI channels around 7.3 μm and 8.7 μm to detect the SO2 and estimate the column loading. The third image is from Sentinel-5P which, as a polar satellite utilising visible light, is only able to view a given location once a day. However, the advantages of the polar product can be seen in the lack of noise and the more complete identification of the SO2 plume.

Credits: Image 1 & 2: Ⓒ Crown Copyright, Met Office, Data: EUMETSAT. Image 3: Met Office 2021, contains modified Copernicus Sentinel data 2021, processed by ESA.

January 2021 - Snow across Iberian Peninsula

11 January 2021

An area of low pressure, named 'Filomena' by Spain's meteorological agency passed over the Iberian Peninsular between January 8th and 10th bringing unusually high snow amounts to parts of Spain and Portugal. Residents of Madrid saw the deepest snow accumulations in the city for over 50 years with 50-60 cm of snow lying in some parts. Relatively cloud-free conditions on January 11th allowed this image to be captured by the NASA/NOAA operated Suomi-NPP satellite, showing the extent of the snow cover over Portugal, Spain and other European counties. This image type uses measurements from the near-infra-red part of the spectrum. This type of false-colour image highlights where snow is lying on the ground as it appears in a bright orange colour. This allows it to be easily differentiated from the white cloud.

Credits:  Image: © Crown copyright, Met Office, Data: NOAA/NASA