Insights into Variations and Potential Long-Range Transport of Atmospheric Aerosols from the Aral Sea Basin in Central Asia

Abstract

The dramatic shrinkage of the Aral Sea in the past decades has inevitably led to an environmental calamity. Existing knowledge on the variations and potential transport of atmospheric aerosols from the Aral Sea Basin (ASB) is limited. To bridge this knowledge gap, this study tried to identify the variations and long-range transport of atmospheric aerosols from the ASB in recent years. The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data were used to gain new insight into the types, variation and long-range transport of atmospheric aerosols from the ASB. The results showed five types of tropospheric aerosols and one type of stratospheric aerosol were observed over the ASB. Polluted dust and dust were the dominant subtypes through the year. Sulfate/other was the only stratospheric aerosol detected. The occurrence frequency of aerosols over the ASB showed obvious seasonal variation. Maximum occurrence frequency of dust appeared in spring (MAM) and that of polluted dust peaked in summer (JJA). The monthly occurrence frequency of dust and polluted dust exhibited unimodal distribution. Polluted dust and dust were distributed over wide ranges from 1 km to 5 km vertically. The multi-year average thickness of polluted dust and dust layers was around 1.3 km. Their potential long-range transport in different directions mainly impacts Uzbekistan, Turkmenistan, Kazakhstan and eastern Iran, and may reach as far as the Caucasus region, part of China, Mongolia and Russia. Combining aerosol lidar, atmospheric climate models and geochemical methods is strongly suggested to gain clarity on the variations and long-range transport of atmospheric aerosols from the Aral Sea Basin.

Identifying Seasonal and Diurnal Variations and the Most Frequently Impacted Zone of Aerosols in the Aral Sea Region

“…Elevated smoke had a percentage of 3% in the daytime, and the percentage in the nighttime was twice as much as that during the daytime. Dust and polluted dust were the two dominant atmospheric aerosol subtypes over the Aral Sea region ( Table 1 ), which is consistent with the findings of Wu et al [ 63 ]. The dust and polluted dust were the two most commonly observed aerosol subtypes for both nighttime and daytime, with the two accounting for over 75% of observed aerosols.…”

“…The Aral Sea’s ongoing declining tendency has not been halted. In 2021, it had a surface area of only 0.56 × 10 4 km 2 , leaving 6.2 × 10 4 km 2 of playa around the present Aral Sea [ 63 ]. The eco-environment around the Aral Sea has deteriorated quickly, and a vast dry lakebed came into being and has turned into a source of fine salt-dust and dust due to strong wind erosion in the Aral Sea region.…”

“…There are seven aerosol subtypes for tropospheric aerosols (dust, polluted dust, clean continental, polluted continental/smoke, elevated smoke, marine, and dusty marine) and four aerosol subtypes for stratospheric aerosols (polar stratospheric aerosol (PSA), volcanic ash, sulfate/other, and smoke) when using a scene classification algorithm [ 73 ]. Following Han et al [ 75 ] and Wu et al [ 63 ], aerosol subtypes with an absolute CAD score (cloud–aerosol discrimination) ≥70 were selected to expound day-night variation in atmospheric aerosols in the Aral Sea region in spring (MAM, from March to May), summer (JJA, from June to August), autumn (SON, from September to November), and winter (DJF, from December to February).…”

“…Wang et al [ 62 ] investigated the temporal characterization of sand and dust storms and their possible driving factors in the Aral Sea region. Wu et al [ 63 ] revealed the night-time variation features of aerosols from the Aral Sea region. However, the seasonal and diurnal variations of aerosols in the Aral Sea region are still unknown, and these variations generally determine their impact on health and climate in this region.…”

“…Up to now, data in terms of the zone most frequently impacted by aerosols from the Aral Sea region have been scarce and limited. Despite previous efforts to analyze the Aral Sea Basin’s aerosol fluctuations and probable long-distance transport [ 61 , 63 ], a lack of seasonal and diurnal variations and the specific most frequently impacted zone in respect of aerosols in the Aral Sea region still exists. In the context of climate change, a more comprehensive and in-depth understanding of the variations and zone most frequently impacted by aerosols from the Aral Sea region is of great practical and scientific significance for taking effective measures to mitigate and deal with environmental and health disasters.…”