Multi-year Raman-polarization lidar profiling in Central Asia: Seasonal analysis of dust and non-dust optical properties over the ACTRIS site in Dushanbe, Tajikistan

Abstract. Dushanbe, located in Central Asia, resides in the global dust belt, fundamental for the emission and transport of dust. The Central Asian Dust EXperiment (CADEX, 2015 to 2016) provided foundational insights into the optical properties of atmospheric dust in Central Asia by means of lidar observations. A follow-up dataset of high-quality multi-year (2019 to 2025) lidar observations from a newly established Aerosol Clouds and Trace Gases Research Infrastructure (ACTRIS) site in Dushanbe, Tajikistan have been analyzed with the goal to deepen the knowledge of the extent, duration and interannual characteristics of the annual dust cycle in the Central Asian region. The dataset consists of automatically processed lidar data, including the application of the POlarization Lidar and PHOtometer Network (POLIPHON) method to separate the measured total particle backscatter coefficient into a dust and non-dust fraction. The study found a pronounced cycle of the dust backscatter coefficient over the course of several years with low values in winter, also in the planetary boundary layer, and a slow onset of the dust season in spring with an increased occurrence of lofted dust layers. The main dust season spans from July to September with a sharp end in September/October. During summer, non-dust particles, likely local pollution, additionally get lifted above the PBL. The PBL is normally well-mixed and shows rather constant contribution of local pollution. These results show the importance of long-term lidar observations in the Central Asian region and the value of high-quality automated processing of the retrieved data.