The spectrum of dust colours over the Arabian Peninsula

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A dust storm formed rapidly over the Arabian peninsula on 1 April

Date & Time
01 April 2015 23:00 UTC
Satellites
Meteosat-10, Metop-B, Suomi-NPP
Instruments
SEVIRI, AVHRR, VIIRS
Channels/Products
Dust RGB, Day-Night Band, Natural Colour RGB, True Colour RGB

Download animation (MPG, 10 MB), Meteosat-10 Dust RGB, 1 April 02:00 UTC–2 April 10:00 UTC
Download animation (MPG, 34 MB), Meteosat-10 Dust RGB, 1 April 00:00 UTC–8 April 06:00 UTC

 

In Depth

by Ivan Smiljanic (DHMZand Hans Peter Roesli (Switzerland)

Figure 1
 
Figure 1: Meteosat-10, Dust RGB, 1 April 23:00 UTC
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An interesting dust event happened on 1 April over the Arabian peninsula. The Dust RGB image (Figure 1) reveal different colours of the same dust, which is transported in different directions and to different layers of the troposphere.

The Meteosat-10 Dust RGB loop from 1–8 April (MPG, 34MB)  shows the evolution of the dust storm. Among other interesting features note the vigorous and multicoloured initial dust uptake and the fast night time progression of the dust front on the night of 1–2 April, which speeds up to a 65km/h low-level jet.

Figure 2a shows the low pressure system apparent from the geopotential field at 500 hPa. Background image is infrared 10.8 um image from the SEVIRI instrument. Dust can be seen as a brighter area on this image, due to the fact that dust itself reduces the radiation coming from the ground ('cooler' area).

Dust could also be seen in visible channels. One example is the Natural Colour RGB image in which dust can be recognized as a light-brownish area (Figure 2b).

 
Figure 2a
 
Figure 2a: Low pressure system apparent from the geopotential field at 500 hPa, 1 April 12:00 UTC
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Figure 2b
 
Figure 2b: Meteosat-10 Natural Colour RGB, 2 April 06:00 UTC
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Early in the afternoon on 1 April the VIIRS Dust/Natural Colour RGB images (Figure 3a & 3b) show a sequence of dust fronts within the initial dust whirl and mostly dust-covered stratocumulus streets. The Dust RGB renders the dusty stratocumuli rather well, whereas they are hard to see in the Natural Colour RGB. There, only the dust-free part shows up (in white at the top left corner of Fig 3b). The shades of colour from pink to magenta reflect the varying density and/or height of the top of the dust.

 
Figure 3a
 
Figure 3a: Suomi-NPP Dust RGB, 1 April 09:34 UTC
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Figure 3b
 
Figure 3b: Suomi-NPP True Colour RGB, 1 April 09:34 UTC
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The Dust RGBs from VIIRS in Fig 4a, 5a and 6a follow the further evolution of the lifted dust at 12 hours intervals until the evening of 2 April and local early morning of 3 April. As it moved down the Arabian peninsula and the Gulf of Persia, accompanied by a large dust sheet over Iran, the whirl pattern started to give way to more linear structures (Fig. 4a). In the early afternoon of 2 April (Figure 5a) the front of the dust area approached the coast of the Arabian Sea. The elongated front outlined the range of hills and rock formations running along the coast. Finally, in the early morning of 3 April (Fig 6a) the dust passed over the lower obstacles and started to be dispersed over the Arabian Sea. The dust then drifted for many days over the sea and also invaded some western states of India, as shown in AVHRR from Metop-B on 6 April 05:16 UTC (light-greyish hue over the land as an extension of the dust over the Arabian Sea, Fig 7). Note that off the Indian coast SSW-NNE oriented sunglint overlays the dust signal. Also looking at the loop from 1–8 April the dust can be seen spreading into African countries (Eritrea, Ethiopia, a bit Somalia), see for example the situation on 4 April at 11.00 UTC.

The Dust RGBs are accompanied by True Colour RGBs or Day-Night-Band (DNB) images, according to the time of the day (Fig 4b, 5b and 6b). The TrueColour RGBs demonstrate the considerable density/thickness of the dust layer – terrain features remained completely hidden. Under the light of the first spring fullmoon also the DNB images show attractive scenes. However, the density thickness of the dust layer was not such to damp noticably the artificial lights sources and occasional gas flare.

 
Figure 4a
 
Figure 4a: Suomi-NPP Dust RGB, 1 April 22:01 UTC
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Figure 4b
 
Figure 4b: Suomi-NPP Day-Night Band, 1 April 22:01 UTC
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Figure 5a
 
Figure 5a: Suomi-NPP Dust RGB, 2 April 09:11 UTC
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Figure 5b
 
Figure 5b: Suomi-NPP True Colour RGB, 2 April 09:11 UTC
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Figure 6a
 
Figure 6a: Suomi-NPP Dust RGB, 2 April 21:42 UTC
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Figure 6b
 
Figure 6b: Suomi-NPP Day-Night Band, 2 April 21:42 UTC
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Figure 7
 
Figure 7: Metop-B AVHRR, 6 April 05:16 UTC
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See also:

Download full resolution image, Suomi-NPP Dust RGB, 3 April 08:53 UTC
Download full resolution image, Suomi-NPP Natural Colour RGB, 3 April 08:53 UTC
Sandstorm envelops Qatar (The Peninsula)
See all our dust cases

 
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