Unexpected High Absorption of Atmospheric Aerosols Over a Western Tibetan Plateau Site in Summer

Abstract

The assessment of atmospheric aerosol radiative effects in the Tibetan Plateau (TP) suffers from large uncertainties due to limited understanding of aerosol physicochemical properties. To quantify aerosol optical properties, size distributions, and chemical compositions in the western TP, an intensive field campaign was carried out at Shiquanhe National Reference Climatological Station from July 8 to August 2, 2019. Unexpected low single scattering albedo (SSA) at 870 nm was found for the fine aerosols with an average value of 0.73 ± 0.18. SSA was even lower than 0.60 in the morning when fine aerosols peaked, indicating high absorption of the fine aerosols induced by anthropogenic activities. Coarse mode aerosols accounted for 70.58% ± 14.98% of the total volume concentration and mineral dust was the most abundant species in total suspended particles with a mass fraction of 48.7%. Fine mode aerosol concentrations showed little dependence on wind speed while coarse mode aerosols and metallic element concentrations exhibited strong positive correlations with wind speed, indicating the importance of wind‐blown dust particles. The present study for the first time quantified key aerosol parameters in the western TP and unexpected high absorption of atmospheric aerosols were found over the site in summer. Our results suggest the need to carefully consider the radiative effects caused by aerosol absorption in the TP region.

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

“…The afternoon peak of aerosols at 15:00 might be related to the peak of wind speed and BLH at the same time (Figures 3b and 4c). Such diurnal variations in aerosols and meteorological parameters are distinct from results observed at typical urban, rural, and other remote sites (e.g., Dumka et al., 2015; Gautam et al., 2011; Guan et al., 2021; Marinoni et al., 2010; Zhang et al., 2021), where they only exhibit unimodal structures during noon or afternoon. Such diurnal variation will be further discussed in Section 3.5.…”

“…The marginal sites on the south slope of the TP (e.g., Jomsom, Dhunche, NCO-P, Kali Gandaki Valley (KGV), Kathmandu Valley, and Naintal) are heavily influenced by fossil fuel combustion and mostly associated with regional circulation from the IGP and westerly air masses from the Middle East, Africa and Europe (Chen et al, 2019;Dhungel et al, 2018;Dumka et al, 2010;Marinoni et al, 2010;Panday & Prinn, 2009). At the same time, some studies on the TP also have analyzed the physical properties of aerosols, such as using the aerosol scattering Ångström exponent (SAE) and absorption Ångström exponent (AAE) to distinguish aerosol size and type, and utilizing single scattering albedo (SSA) to study aerosol absorption and radiative forcing (e.g., Kant et al, 2020;Tian et al, 2023;Zhang et al, 2021;Zhang et al, 2022). However, there is still a lack of the comprehensive analysis of the physical properties and chemical composition of aerosols transported over long-range in the Himalayas (Ram et al, 2010).…”

A New Method for Eliminating Dust Effects When Quantifying the Light Absorption Properties of Brown Carbon

“…For example, the organic components observed by an HR‐ToF‐AMS can be replaced by the organic matter measured by an organic carbon/elemental carbon analyzer (Du et al., 2020). The dust mass concentration can also be reconstructed using the mass concentration of aerosol metal elements (M. Wang et al., 2021; L. Zhang et al., 2021). It is believed that the radiative effects of global BC, BrC, and dust aerosols can be better constrained if the algorithm in this study is extended and applied to globally accumulated aerosol chemistry and absorption data.…”

Fossil and Nonfossil Sources of Winter Organic Aerosols in the Regional Background Atmosphere of China

“…BB is a well-known contributor to OC in emissions, 32 and low coal combustion efficiency can increase the emission of carbona- ceous components. 50 The highest ratio was observed at WLG (average 22.1), which is similar to the OC/EC ratios at Nam Co station (average 24.3) 51 and Shiquanhe station (average 17.4), 52 all located in the Tibetan Plateau. These findings suggest the prevalence of elevated OC/EC ratios, potentially due to high photochemical activity at high altitudes and atmospheric aging during long-range transport.…”