This paper presents the results of the study on columnar aerosol optical and physical properties and radiative effects directly observed over Dushanbe, the capital city of Tajikistan, a NASA AERONET site (equipped with a CIMEL sunphotometer) in Central Asia. The average aerosol optical depth (AOD) and Angstrom exponent (AE) during the observation period from July 2010 to April 2018 were found to be 0.28 +/- 0.20 and 0.82 +/- 0.40, respectively. The highest seasonal AOD (0.32 +/- 0.24), accompanied by the lowest average AE (0.61 +/- 0.25) and fine-mode fraction in AOD (0.39), was observed during summer due to the influence of coarse particles like dust from arid regions. Fine particles were found in significant amounts during winter. The 'mixed aerosol' was identified as the dominant aerosol type with presence of 'dust aerosol' during summer and autumn seasons. Aerosol properties like volume size distribution, single scattering albedo, asymmetry parameter and refractive index suggested the influence of coarse particles (during summer and autumn). Most of the air masses reaching this site transported local and regional emissions, including from beyond Central Asia, explaining the presence of various aerosol types in Dushanbe's atmosphere. The seasonal aerosol radiative forcing efficiency (ARFE) in the atmosphere was found high (>100 Wm(-2)) and consistent throughout the year. Consequently, this resulted in similar seasonally coherent high atmospheric solar heating rate (HR) of 1.5 K day(-1) during summer-autumn-winter, and ca. 0.9 K day(-1) during spring season. High ARFE and HR values indicate that atmospheric aerosols could exert significant implications to regional air quality, climate and cryosphere over the central Asian region and downwind Tianshan and Himalaya-Tibetan Plateau mountain regions with sensitive ecosystems. (C) 2020 Elsevier Ltd. All rights reserved.

The location of Central Asia, almost at the center of the global dust belt region, makes it susceptible for dust events. The studies on atmospheric impact of dust over the region are very limited despite the large area occupied by the region and its proximity to the mountain regions (Tianshan, Hindu Kush-Karakoram-Himalayas, and Tibetan Plateau). In this study, we analyse and explain the modification in aerosols' physical, optical and radiative properties during various levels of aerosol loading observed over Central Asia utilizing the data collected during 2010-2018 at the AERONET station in Dushanbe, Tajikistan. Aerosol episodes were classified as strong anthropogenic, strong dust and extreme dust. The mean aerosol optical depth (AOD) during these three types of events was observed a factor of similar to 3, 3.5 and 6.6, respectively, higher than the mean AOD for the period 2010-2018. The corresponding mean fine-mode fraction was 0.94, 0.20 and 0.16, respectively, clearly indicating the dominance of fine-mode anthropogenic aerosol during the first type of events, whereas coarse-mode dust aerosol dominated during the other two types of events. This was corroborated by the relationships among various aerosol parameters (AOD vs. AE, and EAE vs. AAE, SSA and RRI). The mean aerosol radiative forcing (ARF) at the top of the atmosphere (ARF(TOA)), the bottom of the atmosphere (ARF(BOA)), and in the atmosphere (ARF(ATM)) were -35 +/- 7, -73 +/- 16, and 38 +/- 17 Wm(2) during strong anthropogenic events, -48 +/- 12, -85 +/- 24, and 37 +/- 15 Wm(2) during strong dust event, and -68 +/- 19, -117 +/- 38, and 49 +/- 21 Wm(2) during extreme dust events. Increase in aerosol loading enhanced the aerosol-induced atmospheric heating rate to 0.5-1.6 K day(-1) (strong anthropogenic events), 0.4-1.9 K day(-1) (strong dust events) and 0.8-2.7 K day(-1) (extreme dust events). The source regions of air masses to Dushanbe during the onset of such events are also identified. Our study contributes to the understanding of dust and anthropogenic aerosols, in particular the extreme events and their disproportionally high radiative impacts over Central Asia. (C) 2021 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.

The location of Central Asia, almost at the center of the global dust belt region, makes it susceptible for dust events. The studies on atmospheric impact of dust over the region are very limited despite the large area occupied by the region and its proximity to the mountain regions (Tianshan, Hindu Kush-Karakoram-Himalayas, and Tibetan Plateau). In this study, we analyse and explain the modification in aerosols' physical, optical and radiative properties during various levels of aerosol loading observed over Central Asia utilizing the data collected during 2010-2018 at the AERONET station in Dushanbe, Tajikistan. Aerosol episodes were classified as strong anthropogenic, strong dust and extreme dust. The mean aerosol optical depth (AOD) during these three types of events was observed a factor of similar to 3, 3.5 and 6.6, respectively, higher than the mean AOD for the period 2010-2018. The corresponding mean fine-mode fraction was 0.94, 0.20 and 0.16, respectively, clearly indicating the dominance of fine-mode anthropogenic aerosol during the first type of events, whereas coarse-mode dust aerosol dominated during the other two types of events. This was corroborated by the relationships among various aerosol parameters (AOD vs. AE, and EAE vs. AAE, SSA and RRI). The mean aerosol radiative forcing (ARF) at the top of the atmosphere (ARF(TOA)), the bottom of the atmosphere (ARF(BOA)), and in the atmosphere (ARF(ATM)) were -35 +/- 7, -73 +/- 16, and 38 +/- 17 Wm(2) during strong anthropogenic events, -48 +/- 12, -85 +/- 24, and 37 +/- 15 Wm(2) during strong dust event, and -68 +/- 19, -117 +/- 38, and 49 +/- 21 Wm(2) during extreme dust events. Increase in aerosol loading enhanced the aerosol-induced atmospheric heating rate to 0.5-1.6 K day(-1) (strong anthropogenic events), 0.4-1.9 K day(-1) (strong dust events) and 0.8-2.7 K day(-1) (extreme dust events). The source regions of air masses to Dushanbe during the onset of such events are also identified. Our study contributes to the understanding of dust and anthropogenic aerosols, in particular the extreme events and their disproportionally high radiative impacts over Central Asia. (C) 2021 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.