Large dust plume ejecting off west Africa
15 February 2021 07:00 UTC-19 February 08:00 UTC
In mid-February 2021, Saharan dust headed for Europe; the second major dust outbreak of the season.
21 April 2021
23 February 2021
On Monday 15 February, the Spanish Meteorological Service (AEMET) notified EUMETSAT of an ongoing major dust outbreak over west Africa, which was affecting the weather in the Canary Islands. The ejection of the dust plume from the west coast of Africa can be seen in the enhanced Natural Colours RGB animation (Figure 1). At around 13:30 UTC the dense dust cloud reached the most eastern islands — Fuerteventura and Lanzarote — drastically reducing the visibility and tinting the air orange. In the following hours, powerful wind gusts of up to 80 km/h overwhelmed all the Canary Islands with ‘calima’ — dust in the warm east wind coming from Africa.
The large scale of the 15 February dust outbreak is well captured in the Dust RGB product (Figure 2). The animation shows a simultaneous outbreak of dust at around 9:00 UTC, from a large number of dust sources located in Algeria and Mauritania (so-called dust hot spots), with the biggest source in Algeria, northwest of the Hoggar mountains. Strong Harmattan winds drive the dust clouds westward, while new dust is being lifted in the source areas.
Interestingly, the dust outbreak over West Africa and adjacent Atlantic Ocean, was observed from three different GEO satellites: SEVIRI on Meteosat-11 (nearly NADIR view), SEVIRI on Meteosat-8 (view from east), and ABI on GOES-16 (view from west).
While Meteosat-11 has the best horizontal resolution for the area of west Africa, GOES-16 and Meteosat-8 offer very slant views of the dust cloud, which has the advantage of better detecting thin dust clouds, which appear optically thicker e.g. in the Dust RGB. Also, strong forward scattering of dust particles can improve the dust signal in solar channels, like in the Natural Colours RGB. This is shown in Figure 3, where the dust signal is very strong in the Meteosat-8 image (looks more dramatic than it is) than in the Meteosat-11 image.
Figure 4 shows the GOES-16 perspective of the dust plume over the Atlantic Ocean. According to this loop, thin dust already reached the Canaries in the morning hours of 15 February, before the main dust streamers reached the islands in the afternoon.
Figure 5 shows a series of dust outbreaks over four days, from 15 to 19 February, not only over western Africa but also over central Africa (Bodélé Depression). In summer, the large dust plume would have probably gone westward across the Atlantic to the Americas. But in winter, with the polar front further south, see synoptic situation on 16 February 12:00 UTC (Credit: EUMeTrain), the dust plume encountered a deformation zone over the Atlantic and was partly deflected towards Europe. In fact, a thin dust streamer can be seen reaching Spain on 18 February. News reports noted that parts of Spain could expect to see 'mud rain', as the approaching dust plume combined with a weather front.
On the same day, a dramatic display of the dust cloud over the Atlantic was observed by NOAA-20 VIIRS (Figure 6). The dust appears widespread, with new dust being stirred up over the Bodélé Depression in northeastern Chad, and old dust filaments reaching Spain.
Note: The mid-February dust storm followed an intense event earlier in the month that coated the snow on the Pyrenees and Alps and turned skies orange in France.
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Exceptional Saharan dust transport over the Atlantic Ocean
In June 2020 large amounts of Saharan dust, declared by the media as an "historic Saharan dust plume", travelled on easterly trade winds all the way to the Caribbean and south-eastern parts of the continental US.
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