Large dust plume ejecting off west Africa

By Jochen Kerkmann and José Prieto (EUMETSAT), Miguel Angel Martinez (AEMET), Daniel Lindsey (CIRA)

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.