Vertical distribution, optical properties, and source attribution of summer dust in southern Tajikistan: ground-based observations and model results

Abstract

It is known that dust storms frequently occur during the summer in southern Tajikistan, mainly from satellite-based observations. However, a comprehensive understanding of dust characteristics remains limited due to the scarcity of continuous ground-based measurements. In June of 2023, we established an observational station for investigating the physical and optical properties of dust aerosols in Shaartuz, southern Tajikistan. This study reports dust storms that occurred from July 19 to 26, 2023, focusing on the spatiotemporal distribution and sources of dust aerosols. It is shown that both number and mass concentrations of particles exceeding 10 μm remained substantial throughout the observation period, confirming the persistent presence of coarse-mode dust particles. During the event, PM₁₀ and PM_2.5 concentrations near the ground reached up to 3841 μg/m³ and 695 μg/m³, respectively, coinciding with the dust storm outbreak on July 19. Two coexisting distinct dust layers were found based on statistical analysis of lidar-derived depolarization ratio and color ratio. The lower layer, located below approximately 1.6 km, was predominantly impacted by air masses from northwest Central Asia, whereas the higher elevated layer distributed between 2.2 km and 4 km, was originated from the southern desert regions. Moreover, optical properties of these two dust layers are largely different, indicating that impact of dust aerosols originated from various dust sources on climate in southern Tajikistan may complex. These results highlight the characteristics of the spatiotemporal evolution, transport pathways of dust aerosols, helping to further evaluate their climatic and environmental impacts in southern Tajikistan. These results highlight the characteristics of the spatiotemporal evolution and transport pathways of dust aerosols, and help to further evaluate their climatic and environmental impacts in southern Tajikistan.