Regional Differences in the Light Absorption Properties of Fine Particulate Matter Over the Tibetan Plateau: Insights From HR‐ToF‐AMS and Aethalometer Measurements.

The Tibetan Plateau (TP) has received wide scientific concern in recent decades owing to its important impacts on regional climatic and cryospheric changes, hydrological cycles, and environments. However, our understanding of the spatial distribution of the chemical and optical properties of aerosols is still limited based on prior single‐site observations. In this study, aerosol light absorptions from black carbon (BC) and brown carbon (BrC) were explored and compared among three remote TP sites, including Qomolangma Station (QOMS) on the southern TP, Nam Co Station (NamCo) on the central TP, and Waliguan Observatory on the northeastern TP. Although the aerosol mass concentration at QOMS was less than half of that at Waliguan, the light absorption coefficient of aerosols at QOMS was nearly 5 times higher than that at Waliguan, mainly as a result of more light‐absorbing carbonaceous aerosols on the southern TP due to long‐range transported biomass burning emissions. Specifically, BC dominated aerosol light absorption at all wavelengths, whereas BrC contributed ∼30% of the light absorption at 370 nm at QOMS and ∼20% at Waliguan and NamCo. A major contributor to BrC light absorption at QOMS was biomass burning‐related organic aerosols apportioned from aerosol mass spectrometry measurements. Understanding the significant regional differences in aerosol light absorption properties on the TP is useful for evaluating the regional climatic and environmental effects and validating the model results on aerosol radiative forcing. Plain Language Summary: Brown carbon (BrC) is a group of organic compounds that preferentially absorbs solar light at short wavelengths and has raised wide scientific concerns. However, understanding the physicochemical and optical properties of BrC is still limited, especially in remote regions. Combining two online instruments and adopting a novel approach, our study focuses on the absorption properties of BrC on the Tibetan Plateau (TP), which should be considered carefully in future climate models for evaluating the radiant energy budget and potential impacts on climatic and cryospheric changes over the TP. Key Points: The aerosol light absorption coefficient in the southern region of the Tibetan Plateau (TP) was much higher than that in the northeastern TPBrown carbon contributed significantly to light absorption in the southern TP and was mainly related to biomass burning emissions [ABSTRACT FROM AUTHOR]