Dust aerosol from the Aralkum Desert influences the radiation budget and atmospheric dynamics of Central Asia

Abstract

The Aralkum is a new desert created by the desiccation of the Aral Sea and is an efficient source of dust aerosol which perturbs the regional Central Asian radiation balance. COSMO-MUSCAT model simulations are used to quantify the direct radiative effects (DREs) of Aralkum dust, and investigate the associated perturbations to the atmospheric environment. Considering scenarios of "Past"(end of 20th century) and "Present"(beginning of 21st century) defined by differences in surface water coverage, it is found that in the Present scenario the simulated yearly mean net surface DRE across the Aralkum is -1.34 Wm-2 with a standard deviation (±) of 6.19 Wm-2, of which -0.15 ± 1.19 Wm-2 comes from dust emitted by the Aralkum. In the atmosphere the yearly mean DRE is -0.62 ± 2.91 Wm-2, of which -0.05 ± 0.51 Wm-2 is from Aralkum dust: on the yearly timescale, Aralkum dust is cooling both at the surface and in the atmosphere, due to its optically scattering properties. The daytime surface cooling effect (solar zenith angle ≲ 70-80°) outweighs the nighttime heating effect and the atmospheric daytime (solar zenith angle ≲ 60-70°) heating and nighttime cooling effects. Instantaneous Aralkum dust DREs contribute up to -116 Wm-2 of surface cooling and +54 Wm-2 of atmospheric heating. Aralkum dust perturbs the surface pressure in the vicinity of the Aralkum by up to +0.76 Pa on the monthly timescale, implying a strengthening of the Siberian High in winter and a weakening of the Central Asian heat low in summer. These results highlight the impacts of anthropogenic lakebed dust on regional atmospheric environments.