Modelling of the spatial and temporal patterns of dust storms emitted from the Aralkum (the former Aral Sea) in Central Asia

The formation of the ‘Aralkum’ desert in Central Asia, as a consequence of the severe desiccation of the Aral Sea since the 1960s, has created a major new source of dust aerosol in the region. Recently dried lakebeds can be efficient dust sources, due to the availability of readily erodible sediments, and as a dry lakebed with an area of over 60,000 km² exposed to wind erosion the Aralkum has become a significant driver of dust storms in the region. However due to a paucity of ground-based remote sensing sites in Central Asia it is difficult to quantify the behaviour and consequences of dust activity in the region.

 

Using the dust transport model COSMO-MUSCAT we perform a one-year simulation of dust emission from the Aralkum and other desiccating lakes in Central Asia, exploring the resultant dust emission and transport patterns and assessing the viability of measuring such dust using remote sensing techniques. Making use of the Global Surface Water dataset (produced by the Copernicus Programme) in order to define the surface water coverage in various epochs, we make estimates of dust emissions for the Central Asian and Middle Eastern region under three scenarios: 1) the ‘Past’, representative of water coverage in the 1980s; 2) the ‘Present’, representative of water coverage in the 2010s; and 3) the ‘Aralkum’ scenario, representing only dust emissions from the present-era Aralkum.

 

In the Present scenario we estimate that the Aralkum area (here considered as 43-47°N, 58-62°E) emitted 27.1 Tg of dust over the course of a year from March 2015 to March 2016, while in the Past scenario it emitted 14.3 Tg. However ~68% of these Aralkum emissions occurred when the cloud cover was > 95%, raising questions as to the extent to which dust storm activity from the Aralkum is measurable by standard remote sensing techniques. Exploring the patterns of wind direction and dust emission, we find that of the 27.1 Tg of dust emitted by the Aralkum during the Present scenario, 14.5 Tg were driven by westerly winds, and as a result of this the longest transport pathways are simulated to be to the east. This is in contrast to several previous studies (during previous years) of Aralkum dust which have shown more typical easterly and north-easterly dust emission patterns. Analysis of ERA5 wind data over a 15-year period reveals that there is a high degree of interannual variability as to the direction of the strongest surface winds over the Aralkum, and hence the directions of emitted dust will also vary substantially from year to year.