Radiative cooling and atmospheric perturbation effects of dust aerosol from the Aralkum Desert in Central Asia

Abstract. The Aralkum is a new desert created by the desiccation of the Aral Sea since the 1960s, and is an efficient source of dust aerosol which may perturb 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’ and ‘Present’ defined by differences in surface water coverage, it is found that in the Present scenario the yearly mean net surface DRE across the Aralkum is -1.34±6.19 W m^-2, of which -0.15±1.19 W m^-2 comes from dust emitted by the Aralkum. Meanwhile in the atmosphere the yearly mean DRE is -0.62±2.91 W m^-2, of which -0.05±0.51 W m^-2 comes from Aralkum dust: on the yearly timescale Aralkum dust is cooling both at the surface and in the atmosphere. The daytime surface cooling effect (solar zenith angle ≲70–80°) outweighs both the nighttime heating effect and the corresponding atmospheric daytime (solar zenith angle ≲60–70°) heating and nighttime cooling effects. Instantaneous Aralkum dust DREs contribute up to -116 W m^-2 of surface cooling and +54 W m^-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.