Abstract:Aerosol black carbon (BC) was measured with an Aethalometer™ at Lulang, a high‐altitude station in southeastern Tibetan Plateau (TP), from July 2008 to August 2009. Daily mean BC loadings varied from 57.7 to 5368.9 ng m−3 (grand average ± standard deviation = 496.5 ± 521.2 ng m−3), indicating a significant BC burden even at free tropospheric altitudes. BC loadings were highest during the premonsoon and lowest during the monsoon, and peaks in BC were coincident with high atmospheric boundary layers. Daily peaks… Show more
“…An intensive measurement campaign was conducted from Figure 1. Black carbon concentrations (µg m −3 ) measured at 15 sampling sites in the Himalayas and on the Tibetan Plateau based on the measurements from this study (blue solid circles) and other studies (black solid circles) from Ma et al (2003), Pant et al (2006), Marinoni et al (2010), Stone et al (2010), Babu et al (2011), Engling et al (2011, Li et al (2017), Wan et al (2015), Wang et al (2015a), M. Wang et al (2016), Zhu et al (2016), and Raatikainen et al (2017). More detailed information concerning these studies is summarized in Table S1.…”
Section: Sampling Sitementioning
confidence: 96%
“…However, several recent studies showed that the impact of internal Tibetan sources (e.g., yak dung combustion by local residents) on the atmosphere of the TP should not be overlooked (Chen et al, 2015;Li et al, 2016a;. In the past few decades, a number of field campaigns conducted on the TP have investigated the concentrations, sources, and spatial and temporal variations of BC aerosol (e.g., Engling et al, 2011;Cong et al, 2015;Zhu et al, 2016;Wang et al, 2017;. Recently, research has begun to focus on the light absorption characteristics of BC particles in the atmosphere and snow (Li et al, 2016b, c;.…”
mentioning
confidence: 99%
“…Although some aerosol-related field studies have been conducted on the TP, the BC measurements were mainly made using online or offline filter-based techniques (e.g., aethalometer, thermal/optical reflectance method, and multiangle absorption photometer) (e.g., Engling et al, 2011;Marinoni et al, 2010;Wan et al, 2015;Zhu et al, 2016;Li et al, 2017). These techniques are based on the bulk particle deposition onto the filters, and they cannot provide high time resolution information on of BC size and mixing state.…”
Abstract. Black carbon (BC) aerosol has important effects on the climate and hydrology of the Tibetan Plateau (TP). An intensive measurement campaign was conducted at Lulang (∼ 3300 m a.s.l. – above sea level), southeastern TP, from September to October 2015, to investigate the sources and physicochemical characteristics of refractory BC (rBC) aerosol. The average rBC mass concentration was 0.31 ± 0.55 µg m−3, which is higher than most prior results for BC on the TP. A clear diurnal cycle in rBC showed high values in the morning and low values in the afternoon. A bivariate polar plot showed that rBC loadings varied with wind speed and direction, which also reflected the dominant transport direction. The estimated net surface rBC transport intensity was +0.05 ± 0.29 µg s−1 m−2, indicating stronger transport from outside the TP compared with its interior. Cluster analysis and a concentration-weighted trajectory model connected emissions from north India to the high rBC loadings, but the effects of internal TP sources should not be overlooked. The average mass median diameter (MMD) of rBC was 160 ± 23 nm, with smaller MMDs on rainy days (145 nm) compared with non-rainy days (164 nm). The average number fraction of thickly coated rBC (FrBC) was 39 ± 8 %, and it increased with the O3 mixing ratios from 10:00 to 14:00 LT, indicating that photochemical oxidation played a role in forming rBC coatings. The average rBC absorption enhancement (Eabs) was estimated to be 1.9, suggesting that light absorption by coated rBC particles was greater than for uncoated ones. The Eabs was strongly positively correlated with the FrBC, indicating an amplification of light absorption for internally mixed rBC. For rBC cores < 170 nm, Eabs was negatively correlated with MMD, but it was nearly constant for rBC cores > 170 nm. Our study provides insight into the sources and evolution of rBC aerosol on the TP, and the results should be useful for improving models of the radiative effects of carbonaceous aerosols in this area.
“…An intensive measurement campaign was conducted from Figure 1. Black carbon concentrations (µg m −3 ) measured at 15 sampling sites in the Himalayas and on the Tibetan Plateau based on the measurements from this study (blue solid circles) and other studies (black solid circles) from Ma et al (2003), Pant et al (2006), Marinoni et al (2010), Stone et al (2010), Babu et al (2011), Engling et al (2011, Li et al (2017), Wan et al (2015), Wang et al (2015a), M. Wang et al (2016), Zhu et al (2016), and Raatikainen et al (2017). More detailed information concerning these studies is summarized in Table S1.…”
Section: Sampling Sitementioning
confidence: 96%
“…However, several recent studies showed that the impact of internal Tibetan sources (e.g., yak dung combustion by local residents) on the atmosphere of the TP should not be overlooked (Chen et al, 2015;Li et al, 2016a;. In the past few decades, a number of field campaigns conducted on the TP have investigated the concentrations, sources, and spatial and temporal variations of BC aerosol (e.g., Engling et al, 2011;Cong et al, 2015;Zhu et al, 2016;Wang et al, 2017;. Recently, research has begun to focus on the light absorption characteristics of BC particles in the atmosphere and snow (Li et al, 2016b, c;.…”
mentioning
confidence: 99%
“…Although some aerosol-related field studies have been conducted on the TP, the BC measurements were mainly made using online or offline filter-based techniques (e.g., aethalometer, thermal/optical reflectance method, and multiangle absorption photometer) (e.g., Engling et al, 2011;Marinoni et al, 2010;Wan et al, 2015;Zhu et al, 2016;Li et al, 2017). These techniques are based on the bulk particle deposition onto the filters, and they cannot provide high time resolution information on of BC size and mixing state.…”
Abstract. Black carbon (BC) aerosol has important effects on the climate and hydrology of the Tibetan Plateau (TP). An intensive measurement campaign was conducted at Lulang (∼ 3300 m a.s.l. – above sea level), southeastern TP, from September to October 2015, to investigate the sources and physicochemical characteristics of refractory BC (rBC) aerosol. The average rBC mass concentration was 0.31 ± 0.55 µg m−3, which is higher than most prior results for BC on the TP. A clear diurnal cycle in rBC showed high values in the morning and low values in the afternoon. A bivariate polar plot showed that rBC loadings varied with wind speed and direction, which also reflected the dominant transport direction. The estimated net surface rBC transport intensity was +0.05 ± 0.29 µg s−1 m−2, indicating stronger transport from outside the TP compared with its interior. Cluster analysis and a concentration-weighted trajectory model connected emissions from north India to the high rBC loadings, but the effects of internal TP sources should not be overlooked. The average mass median diameter (MMD) of rBC was 160 ± 23 nm, with smaller MMDs on rainy days (145 nm) compared with non-rainy days (164 nm). The average number fraction of thickly coated rBC (FrBC) was 39 ± 8 %, and it increased with the O3 mixing ratios from 10:00 to 14:00 LT, indicating that photochemical oxidation played a role in forming rBC coatings. The average rBC absorption enhancement (Eabs) was estimated to be 1.9, suggesting that light absorption by coated rBC particles was greater than for uncoated ones. The Eabs was strongly positively correlated with the FrBC, indicating an amplification of light absorption for internally mixed rBC. For rBC cores < 170 nm, Eabs was negatively correlated with MMD, but it was nearly constant for rBC cores > 170 nm. Our study provides insight into the sources and evolution of rBC aerosol on the TP, and the results should be useful for improving models of the radiative effects of carbonaceous aerosols in this area.
“…There is growing concern that glaciers on the TP are in retreat, due in part to the influence of atmospheric black carbon (BC) and dust which are light‐absorbing materials (William et al, ). The optical properties and radiative effects of these two substances have been well documented over the past decades (e.g., Qu et al, ; Wang, Cao, Han, Tian, Zhang, et al, ; Wang, Cao, Han, Tian, Zhu, et al, ; Zhang et al, ; Zhao, Wang, et al, ). More recently, a group of colored organic compounds, collectively known as brown carbon (BrC), has been found to absorb sunlight, especially at short wavelengths (Andreae & Gelencsér, ).…”
The optical properties of atmospheric secondary brown carbon (BrC) aerosol are poorly understood because of its chemical complexity, and this has hampered quantitative assessments of the impacts of this light‐absorbing material on glaciers on the Tibetan Plateau. For this study, a statistical approach was developed to investigate BrC light absorption over the southeastern margin of the Tibetan Plateau. Secondary sources for BrC were more important for absorption than primary ones. A diurnal cycle in secondary BrC absorption was explained by the formation of light‐absorbing chromophores by photochemical oxidation after sunrise followed by photobleaching of the chromophores under the more oxidizing conditions as the day progressed. Multimethod analyses showed that biomass burning in northern Burma and along the Sino‐Burmese border was the most important source for the secondary BrC. The mean integrated simple forcing efficiency was 79 W/g, indicating that secondary BrC can cause substantial radiative effects.
“…An intensive measurement campaign was conducted from Figure 1. Black carbon concentrations (µg m −3 ) measured at 15 sampling sites in the Himalayas and on the Tibetan Plateau based on the measurements from this study (blue solid circles) and other studies (black solid circles) from Ma et al (2003), Pant et al (2006), Marinoni et al (2010), Stone et al (2010), Babu et al (2011), Engling et al (2011), Zhao et al (2012), Li et al (2017), Wan et al (2015), Wang et al (2015a), M. Wang et al (2016), Zhu et al (2016), and Raatikainen et al (2017). More detailed information concerning these studies is summarized in Table S1.…”
Black carbon (BC) aerosol has important effects on the climate and hydrology of the Tibetan Plateau (TP). An intensive measurement campaign was conducted at Lulang (∼ 3300 m a.s.l.-above sea level), southeastern TP, from September to October 2015, to investigate the sources and physicochemical characteristics of refractory BC (rBC) aerosol. The average rBC mass concentration was 0.31 ± 0.55 µg m −3 , which is higher than most prior results for BC on the TP. A clear diurnal cycle in rBC showed high values in the morning and low values in the afternoon. A bivariate polar plot showed that rBC loadings varied with wind speed and direction, which also reflected the dominant transport direction. The estimated net surface rBC transport intensity was +0.05 ± 0.29 µg s −1 m −2 , indicating stronger transport from outside the TP compared with its interior. Cluster analysis and a concentration-weighted trajectory model connected emissions from north India to the high rBC loadings, but the effects of internal TP sources should not be overlooked. The average mass median diameter (MMD) of rBC was 160 ± 23 nm, with smaller MMDs on rainy days (145 nm) compared with non-rainy days (164 nm). The average number fraction of thickly coated rBC (F rBC) was 39 ± 8 %, and it increased with the O 3 mixing ratios from 10:00 to 14:00 LT, indicating that photochemical oxidation played a role in forming rBC coatings. The average rBC absorption enhancement (E abs) was estimated to be 1.9, suggesting that light absorption by coated rBC particles was greater than for uncoated ones. The E abs was strongly positively correlated with the F rBC , indicating an amplification of light absorption for internally mixed rBC. For rBC cores < 170 nm, E abs was negatively correlated with MMD, but it was nearly constant for rBC cores > 170 nm. Our study provides insight into the sources and evolution of rBC aerosol on the TP, and the results should be useful for improving models of the radiative effects of carbonaceous aerosols in this area. 1 Introduction The Tibetan Plateau (TP) is the world's largest high-elevation region. It holds the largest ice mass on the planet outside the polar regions and is sometimes called the Earth's "Third Pole" (Yao et al., 2008). The snow and associated glacial meltwater on the TP provides fresh water for drinking and irrigation for more than 1 billion people downstream (Immerzeel et al., 2010). The TP exerts significant thermal and dynamic impacts on hydrological processes in South and East Asia. For example, changes in the area covered by glaciers and snowpack on the TP affect the heat fluxes and water exchange between the atmosphere and the earth's surface, and that, in turn, affects the atmospheric circulation
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