Supplementary material to "Measurement report: Long-term changes in black carbon and aerosol optical properties from 2012 to 2020 in Beijing, China"

Abstract. Atmospheric aerosols play an important role in the radiation balance of the earth–atmosphere system. However, our knowledge of the long-term changes in equivalent black carbon (eBC) and aerosol optical properties in China is very limited. Here we analyze the 9-year measurements of eBC and aerosol optical properties from 2012 to 2020 in Beijing, China. Our results showed large reductions in eBC by 71 % from 6.25 ± 5.73 µg m−3 in 2012 to 1.80 ± 1.54 µg m−3 in 2020 and 47 % decreases in the light extinction coefficient (bext, λ = 630 nm) of fine particles due to the Clean Air Action Plan that was implemented in 2013. The seasonal and diurnal variations of eBC illustrated the most significant reductions in the fall and at nighttime, respectively. ΔeBC / ΔCO also showed an annual decrease from ∼ 7 to 4 ng m−3 ppbv−1 and presented strong seasonal variations with high values in spring and fall, indicating that primary emissions in Beijing have changed significantly. As a response to the Clean Air Action Plan, single-scattering albedo (SSA) showed a considerable increase from 0.79 ± 0.11 to 0.88 ± 0.06, and mass extinction efficiency (MEE) increased from 3.2 to 3.8 m2 g−1. These results highlight the increasing importance of scattering aerosols in radiative forcing and a future challenge in visibility improvement due to enhanced MEE. Brown carbon (BrC) showed similar changes and seasonal variations to eBC during 2018–2020. However, we found a large increase of secondary BrC in the total BrC in most seasons, particularly in summer with the contribution up to 50 %, demonstrating an enhanced role of secondary formation in BrC in recent years. The long-term changes in eBC and BrC have also affected the radiative forcing effect. The direct radiative forcing (ΔFR) of BC decreased by 67 % from +3.36 W m−2 in 2012 to +1.09 W m−2 in 2020, and that of BrC decreased from +0.30 to +0.17 W m−2 during 2018–2020. Such changes might have important implications for affecting aerosol–boundary layer interactions and the improvement of future air quality.

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Measurement report: Long-term changes in black carbon and aerosol optical properties from 2012 to 2020 in Beijing, China

10.5194/acp-2021-637 ◽

2021 ◽

Author(s):

Jiaxing Sun ◽

Zhe Wang ◽

Wei Zhou ◽

Conghui Xie ◽

Cheng Wu ◽

...

Keyword(s):

Optical Properties ◽

Black Carbon ◽

Seasonal Variations ◽

Radiative Forcing ◽

Aerosol Optical Properties ◽

Seasonal And Diurnal Variations ◽

Long Term Changes ◽

Clean Air ◽

Beijing China

Abstract. Atmospheric aerosols play an important role in radiation balance of the earth-atmosphere system. However, our knowledge of the long-term changes in black carbon (BC) and aerosol optical properties in China are very limited. Here we analyze the nine-year measurements of BC and aerosol optical properties from 2012 to 2020 in Beijing, China. Our results showed large reductions in eBC by 67 % from 5.54 ± 5.25 µg m−3 in 2012 to 1.80 ± 1.54 µg m−3 in 2020, and 47 % decreases in light extinction coefficient (bext, λ = 630 nm) of fine particles due to clean air action plan since 2013. The seasonal and diurnal variations of eBC illustrated the most significant reductions in the fall and night time, respectively. ΔeBC/ΔCO also showed an annual decrease from ~6 to 4 ng m−3 ppbv−1 and presented strong seasonal variations with high values in spring and fall, indicating that primary emissions in Beijing have changed significantly. As a response to clean air action, single scattering albedo (SSA) showed a considerable increase from 0.79 ± 0.11 to 0.88 ± 0.06, and mass extinction efficiency (MEE) increased from 3.2 to 3.8 m2 g−1. These results highlight an increasing importance of scattering aerosols in radiative forcing, and a future challenge in visibility improvement due to enhanced MEE. Brown carbon (BrC) showed similar changes and seasonal variations to eBC during 2018–2020. However, we found a large increase of secondary BrC in the total BrC in most seasons, particularly in summer with the contribution up to 50 %, demonstrating an enhanced role of secondary formation in BrC in recent years. The long-term changes in eBC and BrC have also affected the radiative forcing effect. The direct radiative forcing (ΔFR) of BC decreased by 64 % from +3.00 W m−2 in 2012 to +1.09 W m−2 in 2020, and that of BrC decreased from +0.30 to +0.17 W m−2 during 2018–2020. Such changes might have important implications in affecting aerosol and boundary-layer interactions and the future air quality improvement.

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Supplementary material to "Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China"

10.5194/acp-2018-788-supplement ◽

2018 ◽

Author(s):

Conghui Xie ◽

Weiqi Xu ◽

Junfeng Wang ◽

Qingqing Wang ◽

Dantong Liu ◽

...

Keyword(s):

Optical Properties ◽

Aerosol Optical Properties ◽

Brown Carbon ◽

Supplementary Material ◽

Beijing China

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Aerosol optical properties and mixing state of black carbon in the Pearl River Delta, China

Atmospheric Environment ◽

10.1016/j.atmosenv.2016.02.003 ◽

2016 ◽

Vol 131 ◽

pp. 196-208 ◽

Cited By ~ 24

Author(s):

Haobo Tan ◽

Li Liu ◽

Shaojia Fan ◽

Fei Li ◽

Yan Yin ◽

...

Keyword(s):

Optical Properties ◽

Black Carbon ◽

Pearl River Delta ◽

River Delta ◽

Pearl River ◽

Mixing State ◽

Aerosol Optical Properties ◽

The Pearl River Delta ◽

The Pearl River

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A closure study of aerosol optical properties as a function of RH using a κ-AMS-BC-Mie model in Beijing, China

Atmospheric Environment ◽

10.1016/j.atmosenv.2018.10.015 ◽

2019 ◽

Vol 197 ◽

pp. 1-13 ◽

Cited By ~ 6

Author(s):

Jianan Zou ◽

Shuanghong Yang ◽

Bo Hu ◽

Zirui Liu ◽

Wenkang Gao ◽

...

Keyword(s):

Optical Properties ◽

Aerosol Optical Properties ◽

Beijing China

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Sensitivity of aerosol radiative effects to different mixing assumptions in the AEROPT 1.0 submodel of the EMAC atmospheric-chemistry–climate model

Geoscientific Model Development ◽

10.5194/gmd-7-2503-2014 ◽

2014 ◽

Vol 7 (5) ◽

pp. 2503-2516 ◽

Cited By ~ 23

Author(s):

K. Klingmüller ◽

B. Steil ◽

C. Brühl ◽

H. Tost ◽

J. Lelieveld

Keyword(s):

Optical Properties ◽

Radiative Transfer ◽

Black Carbon ◽

Atmospheric Chemistry ◽

Radiative Forcing ◽

Climate Model ◽

Mixing Rule ◽

Aerosol Optical Properties ◽

Internal Mixing ◽

Aerosol Radiative

Abstract. The modelling of aerosol radiative forcing is a major cause of uncertainty in the assessment of global and regional atmospheric energy budgets and climate change. One reason is the strong dependence of the aerosol optical properties on the mixing state of aerosol components, such as absorbing black carbon and, predominantly scattering sulfates. Using a new column version of the aerosol optical properties and radiative-transfer code of the ECHAM/MESSy atmospheric-chemistry–climate model (EMAC), we study the radiative transfer applying various mixing states. The aerosol optics code builds on the AEROPT (AERosol OPTical properties) submodel, which assumes homogeneous internal mixing utilising the volume average refractive index mixing rule. We have extended the submodel to additionally account for external mixing, partial external mixing and multilayered particles. Furthermore, we have implemented the volume average dielectric constant and Maxwell Garnett mixing rule. We performed regional case studies considering columns over China, India and Africa, corroborating much stronger absorption by internal than external mixtures. Well-mixed aerosol is a good approximation for particles with a black-carbon core, whereas particles with black carbon at the surface absorb significantly less. Based on a model simulation for the year 2005, we calculate that the global aerosol direct radiative forcing for homogeneous internal mixing differs from that for external mixing by about 0.5 W m−2.

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