Physical Properties, Chemical Components, and Transport Mechanisms of Atmospheric Aerosols Over a Remote Area on the South Slope of the Tibetan Plateau

The physicochemical properties and origins of atmospheric aerosols in the Tibetan Plateau (TP) region are a research topic of great interest, but an in-depth understanding of this topic is challenging, partially due to a lack of intensive in situ observations. Thus, a field campaign was conducted over Yadong, a remote area on the south slope of the TP from June 11 to 31 August 2021. The aerosol loading was low, with a black carbon mass concentration of 147.4 +/- 98.4 ng center dot m-3. Aerosol single-scattering albedo was low (0.73 +/- 0.11 at 550 nm) and increased from 450 to 700 nm wavelength. Organic matter (OM) accounting for 69.6% of the total aerosol mass and relatively high secondary organic carbon ratios, highlighting the importance of secondary formation. An interesting phenomenon observed was that the evolution of aerosols was mainly characterized by diurnal variation, which could not be explained by large-scale atmospheric processes such as Indian summer monsoon. Instead, it was found that regional mountain-valley winds between the Himalayas and South Asia transported polluted air masses toward the TP, especially in the afternoon when regional valley wind are expected to be the strongest and the boundary layer in South Asia is deepest. Additionally, daytime local valley wind further elevated these aerosols to higher altitudes on the TP. This paper provides insights into the transport mechanisms of aerosols from South Asia to the TP. These findings are of great importance since aerosols exhibit significant diurnal variations in the TP region. Previous studies focused on the analysis of the physical or chemical properties of aerosols on the Tibetan Plateau, but this study provides a comprehensive examination of both. The findings reveal that aerosols on the southern slope of the Tibetan Plateau exhibit strong absorption efficiency. Aerosol single-scattering albedo was low (0.73 +/- 0.11 at 550 nm), which may be attributed to aerosol secondary generation and coating. Finally, the mechanism of pollutant transport from South Asia to the Tibetan Plateau was analyzed relies on site observations, satellite, and reanalysis data to highlight the link between diurnal variations of pollutants and transport mechanism. The specific transport mechanism be understood uniformly across different scales, including Indian summer monsoon, regional mountain-valley winds between the Himalayas and South Asia, and local mountain-valley winds circulation. Aerosol single-scattering albedo was low (0.73 +/- 0.11 at 550 nm) and secondary organic matter was the major aerosol component The evolution of aerosols was mainly characterized by diurnal variation that was related to transport mechanism over Yadong The Himalayas-South Asia regional mountain-valley winds combined with local mountain-valley winds transport aerosols to the Tibetan Plateau