In late March 2018 a cold outbreak drove Saharan dust from the Atlas mountains down to the south-west coast of Africa and on to Greece.
29 January 2021
20 March 2018
By Hans Peter Roesli (Switzerland), Charalampos Karvelis (Hellenic National Meteorological Service), Jochen Kerkmann (EUMETSAT), Ivan Smiljanic (CGI) and Maria Putsay (Hungarian Meteorological Service)
Towards the end of March 2018 exceptionally frequent and vast dust outbreaks occurred over the Sahara, spreading dust across southern Europe, into the tropical belt of Africa, and over the Atlantic.
The long image sequence of Dust RGBs from Meteosat-11 from 20 March 12:00 UTC to 26 March 12:00 UTC gives an overview over the whole event (Figure 1).
Unlike the usual mostly Harmattan or convective-driven March events, this dust season was dominated by cold-air outbreaks from low pressure areas crossing the Mediterranean.
On 20 March a cold front from one of these lows crossed the Atlas mountain range and lifted dust from the Moroccan-Algerian Sahara. Usually, in events like this, the lifted dust remains limited to the northern parts of the Sahara and may be driven east-north-eastward over the Mediterranean and beyond (see Previous Case Studies below)
In more exceptional cases the dust moves much more south down to the Sahel belt, where it then gets blocked, with its western branch fanning out into the Atlantic (see previous Case Studies below).
In this case, on 21 March at an average speed of 45 km/h, the dust veil travelled down to the western Sahel (Figure 2). From there it spread even further south, although more slowly, into the tropical belt and the African west coast.
From the west coast part of it was blown off over the Atlantic, as shown on 23 March in the false colour RGB (bands IR3.74/NIR1.61/VIS0.659) from the SLSTR instrument on Sentinel-3A (Figure 3).
This can also be seen on the animated sequence of Natural Colour RGBs from Meteosat-11 from 22 March 08:00 UTC–25 March 18:00 UTC (Figure 4), and in four daily VIIRS True Color RGBs in the NASA Earth Observatory case study Bits of the Sahara on the Move .
The arrival of the dust-laden air in the Sahel between 21 and 23 March was well documented by the midnight radio soundings from Tamanrasset in Mali and Niamey in Niger . Both soundings showed a significant fall in temperature and a pick up of northerly winds below 700hPa.
On 22 March, simultaneously with the southward travelling dust fan over the Sahara, pre-frontal winds lifted dust over Libya and drove it out into the central-eastern Mediterranean. On the right panel of Figure 2 two parallel tongues of dust can be identified. The right-hand one shows the classical pink colour of the Dust RGB, pointing to dense dust extending vertically well above the boundary layer. The left-hand one, of a deep blue colour, lacks contrast and points to thin dust trapped in the maritime boundary layer.
This low-level dust appears much better in cyan colouring in the Night Cloud Microphysics RGB (Figure 5). On the same night, the dust front over the Sahara also appeared in cyan.
For an in-depth explanation of the cyan colour see the EUMeTrain Colour Interpretation Guide.
Dust over Greece
It was one of the largest events of dust advection to Greece from North Africa. Dust levels in the atmosphere were extremely high in the southern part of the country, especially in the Crete Island and Cyclades (see Figures 6 and 7).
In fact, the African dust covered the entire country (including Athens) and concentrations were the highest in the last ten years. Forecasters were able to use satellite imagery as an aid in issuing warnings.
Other African dust cases
Large Dust Fan (Spanish Dancer) over West Africa
A cyclone over Algeria pushes cold air southward over West Africa, causing a synoptic scale dust outbreak, in early March 2019.
Large dust fan over Northwest Africa
The imagery shows a cyclone over Tunisia and the related cold air outbreak from Western Europe to Northwest Africa, which caused a major dust storm.
Sahara dust outbreak across the Atlantic
On 3 March 2004, the massive storm formed a huge arc of thick dust that swept over the Canary Islands.
Dust storm over West Africa and the Canary Islands
Early March 2004, a cold air outbreak from Europe to Western Africa caused a major dust storm over large parts of West Africa.
Latest case studies
Large smoke plume from wildfires in Russia
By Mark Higgins (EUMETSAT), Sancha Lancaster (Pactum) and Ilaria Parodi (CGI)
Devastating floods in western Europe
Catastrophic floods hit Germany, Belgium and parts of West Europe mid July 2021.
Catastrophic tornado in the Czech Republic
Satellites' view on the catastrophic tornado case on 24 June 2021 in the Czech Republic.
Tracking the Gulf Stream with satellite data
Using satellite data from multiple satellite instruments to track the Gulf Stream in 2020 and 2021.