Dust crossing the Gulf of Aden

By Jochen Kerkmann (EUMETSAT)

February to June is the peak season for large-scale dust outbreaks over the Arabian Peninsula and the Middle East (see example from 20 February 2008 at 05:15 UTC, Meteosat-9, Natural Colour RGB). Usually, the progress of the dust clouds towards the south slows down over the southern part of the Arabian Peninsula where the diffluent flow encounters southerly winds from the Arabian Sea.

The peculiarity of the case shown below is the fact that the dust cloud was blown far out into the Arabian Sea, crossing the Gulf of Aden and passing the island of Socotra (Yemen). This can be seen on the Meteosat-7 image below which shows thick dust plumes, bordered by thick banks of clouds, blowing over the ocean waters. The latter mark the southern border of the dust outbreak and represent, in meteorological terms, a convergence line of the lower-level winds.

It should be noted that the dust clouds seen in the Meteosat-7 image over the Gulf of Oman, close to Iran and Pakistan, are part of a second wave of dust outbreaks that usually occur when, with the eastward movement of the cold front, the Shamal winds blow dust from Iran, Afghanistan and/or Pakistan to the Arabian Sea (see example from 22 February 2008 at 05:00 UTC, Meteosat-7, VIS). Occasionally, this second wave of dust crosses the Gulf of Oman and reaches Oman itself, often with severe consequences for air and road traffic. An example for this is reported in the case study Dust crossing the Gulf of Oman (8 May 2005).

Additional information (1 February 2011)

The image below shows the MSG (Meteosat-9) Dust RGB product taken about three hours after the above shown Meteosat-7 visible image. Note how difficult it is to see the dust cloud over the Indian Ocean. To verify the height of the dust clouds we have plotted the Calipso vertical profile in the upper left part of the image.

The Calipso track is given by the green line. The dust cloud is outlined by the dark red line. As expected from the interpretation of the colour of the dust cloud, (relatively weak magenta), the dust cloud is low level dust with a top at around 1km. In the southern part, the dust is embedded in a stratocumulus cloud field as indicated by the stronger Calipso signal (white colour).

Further north, close to the Oman coastline, the dust cloud reaches higher levels of up to 2km. Note the stronger colour of the low level dust cloud over southern Iran, which is due to the higher temperatures of the underlying land surface (the image is around local noon).

Additional content

Met-9 Dust RGB image (1 February 06:30 UTC)
Met-9 Dust RGB animation (hourly, 31 January 08:00 UTC–2 February 07:00 UTC)
Terra MODIS Truecolour RGB image (2 February 06:20 UTC, source: NASA)
Aqua MODIS Truecolour RGB image (2 February 09:25 UTC, source: NASA)