In late January/early February a large dust plume swept north east from Africa and over the Mediterranean Sea.
09 August 2021
31 January 2015
Picked up by an advection of westerly winds dust from Algeria travelled towards the north east, far beyond the Black Sea.
Isotachs (contour lines showing constant wind speed areas) that are overlaid on the Meteosat-10 Airmass RGB, 31 January 12:00 UTC (Figure 1), revealed the position of the high level jet, situated over the west Mediterranean Sea. This jet was responsible for the westerly low level advection of the relatively warm airmass situated over northern Algeria.
This advection picked up dust particles from the ground, and over the next few days the dust travelled with the prevailing flow beyond the Black Sea.
The dust plume's journey from Algeria to the Black Sea can be followed on the animated loop of the Dust RGB, 31 January 13:00 UTC–2 February 06:00 UTC.
The detection of the dust over water surfaces is very easy with Natural Colour RGB imagery, especially in the early morning hours when there is a lot of forward scattering coming from the dust particles, towards the satellite.
Some dust patches are even more pronounced in the Natural Colour RGB than in Dust RGB (Figure 2), but only when seen over the water surfaces (see east Mediterranean). In the Natural Colour RGB the dust is almost invisible over the African continent.
The VIIRS imager on Suomi-NPP also provided spectacular imagery of the dust streak. The good performance of the Dust RGB over land and water, during the day and at night, is established once again with this case (see Figures 3 and 6).
During the day the Dust RGB (Figure 3) can be compared to the Natural Colour RGB (Figure 4), at 375m spatial resolution. Although it is difficult to identify the thinning dust veil over western Turkey, the image brings out the wave cloud further to the east, showing that the south-westerly winds transported the dust.
VIIRS at night and under good moonlight offers the Day-Night band (Figure 5) for visible clues.
As the dust event happened just a few days before the full Moon, good lighting conditions could be expected. In fact, careful enhancement uncovers the moonlit dust veil between Libya and the Aegean Sea.
Over Turkey some wave cloud persisted and some strong city lights can be identified, e.g. those of Ankara.
Note that this large, synoptic-scale dust outbreak was well forecast by specialist dust NWP models, as seen in the total dust load forecast from Athens University.
Saharan Dust over the Mediterranean Sea (NASA Earth Observatory)
Animated gif of VIIRS True Colour imagery (CIMSS Blog)
The spectacular Saharan dust outbreak of 1 February 2015 (in German, Wetterzentrale Forum)
A strong outbreak of Saharan Dust (Michael Sachweh/YouTube)
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