Transport of African-Arabian dust to Pakistan & north India

In early May, the Mediterranean saw very persistent low pressure centres. Although not unusual for this month some of them moved off into the Middle East, causing several deep, cold-air outbreaks. These then lifted dust between the north-eastern African coast and the Arabian peninsula.

Usually, such dust storms settle when reaching the Arabian Sea and/or the Sea of Oman and its eastern coast. However, on this occasion, between 12 and 15 May, the dust moved further east and moved into Iran, Pakistan, Afghanistan and North India, as shown on the sequence of Dust RGBs from Meteosat-8, between 6 and 15 May (Figure 2).

Although such widespread dust transport had certainly also happened in the past, this was the first time it was documented in its full extent by the multi-spectral SEVIRI instrument while in the IODC position.

In more detail, on 6 May, the animation shows the formation of a southward moving dust front, starting over the Egypt-Libya border regions, and a simultaneous dust outbreak from convective downdrafts over Somalia (Figure 3). The dust front with a dust veil at its back undercut the ‘convective’ dust on 7 May (Figure 4).

On 8 May the dust was integrated into a much more extended dust front stemming from a new and stronger cold-air outbreak that covered the whole Arabian peninsula (Figure 5).

Over the following days the dust situation became more complex (Figure 6) and by 12 May a large extended group of 'dust parcels' headed east (Figure 1) into Iran, Pakistan, Afghanistan and north India.

On 13 May an overpass of a GOME-2 instrument on Metop-A produced a map of the Aerosol Index (AAI) from EUMETSAT’s Atmospheric Composition SAF (AC SAF). A comparison (Figure 7) with the Dust RGB around the same time (GOME area outlined in white) shows a reasonable match to the dust-affected areas.

An overpass of the OLCI instrument on Sentinel-3A allowed for another comparison — a Tristimulus RGB with a Dust RGB (OLCI scene outlined in white on Figure 8). Due to the unfavourable (in terms of strong backward or forward scattering by the aerosol) timing of the solar illumination (local early afternoon) the OLCI scene only showed a very faint dust veil, although the Dust RGB showed relatively strong dust signals.

There are other features to discover in the animation, such as the sea breeze fronts along the coast of Balochistan provinces of Iran and Pakistan, or the dust lifted over the Taklamakan Desert in north-west China on 8 and 15 May at 12:00 UTC (Figure 9).