Satellite image of the month

March 2022 - Saharan dust over Spain and France

15 March 2022

NOAA20 Saharan dust images 20220315

A large cloud of desert dust, created by storms in the Sahara desert, is carried northwards over Spain and France by the wind, as can be clearly seen in this pair of VIIRS satellite images from the NASA/NOAA-operated satellite NOAA-20. Both images show the situation at 1318 UTC on the 15th March 2022. In the left-hand true colour image the dust cloud appears as a sandy light brown colour, whereas in the right-hand image, an infrared false-colour ("Dust RGB") composite, the dust appears as bright pink/magenta colours.

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


February 2022 - Storm Eunice

18 February 2022

Storm Eunice was named by the Met Office on 14 February 2022, and resulted in the issue of two rare red weather warnings, one for areas of South Wales and South West England and one for London and the South East of England, prior to the storm crossing the UK on 18 February. The left-hand image above shows a visible image taken from the geostationary Meteosat-11 satellite at around 1115 UTC on the morning of 18 February. At a similar time, a wind gust of 122 miles per hour (55 metres per second) was recorded at the Needles, Isle of Wight, provisionally setting a record for the fastest wind gust ever recorded in England.

The right-hand image above shows measured surface winds near the centre of Eunice at a similar time. The colours on the map indicate the instantaneous strength of the wind, with each point representing an average over an area around 30 km across; yellow shades represent the strongest winds (approaching 30 metres per second) for the swath covered, whilst the arrows show the wind direction. These wind data are derived from the Advanced Scatterometer (ASCAT) instrument on-board the polar-orbiting Metop-B satellite. From an orbit of over 800 km above the Earth’s surface ASCAT cannot measure the wind directly. Instead the radar sends down pulses of microwave energy and measures the return signal which is scattered back from the ocean surface. As the wind strength increases the ocean surface becomes rougher and more energy is back-scattered towards the satellite. By taking multiple measurements of the same patch of ocean an estimate of the surface (10 m height) wind speed and direction can be made.

Credits: Images: © Crown copyright, Met Office, Data: EUMETSAT/KNMI


January 2022 - Hunga Tonga-Hunga Ha'apai Eruption

15 January 2022

A submarine volcano, located in the South Pacific Island nation of Tonga, began erupting in late December 2021. Activity built in the following weeks, coming to a head on January 15th with a ferocious explosion in the early hours of the day.

The images above show the eruption on January 15th, captured by GOES-17, a geostationary satellite operated by NASA/NOAA. The images are ‘natural colour RGB’ which uses a combination of visible and near infra-red channels to provide a view close to what the human eye would see, except ice clouds show up as a cyan colour. The left image (04:30 UTC), and right image (05:00 UTC) help illustrate the rapid development of the volcano plume.

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