Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 18, 1419-1436, 2018
https://doi.org/10.5194/acp-18-1419-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
01 Feb 2018
The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China
Bingliang Zhuang1, Tijian Wang1, Jane Liu1,2, Huizheng Che3, Yong Han1, Yu Fu4, Shu Li1, Min Xie1, Mengmeng Li1, Pulong Chen1, Huimin Chen1, Xiu-qun Yang1, and Jianning Sun1 1School of Atmospheric Sciences, CMA-NJU Joint Laboratory for Climate Prediction Studies, Jiangsu Collaborative Innovation Center for Climate Change, Nanjing University, Nanjing 210023, China
2Department of Geography and Planning, University of Toronto, Toronto, M5S 3G3, Canada
3Key Laboratory of Atmospheric Chemistry (LAC), Chinese Academy of Meteorological Sciences (CAMS), CMA, Beijing, 100081, China
4Dalian Weather Modification Office, Dalian, 116001, China
Abstract. The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions than satellite retrievals. An initial analysis reveals the characteristics of the optical properties of different types of fractionated aerosols in the western YRD. The total aerosols, mostly composed of scattering components (93.8 %), have mean optical depths of 0.65 at 550 nm and refractive index of 1.44 + 0.0084i at 440 nm. The fine aerosols are approximately four times more abundant and have very different compositions from coarse aerosols. The absorbing components account for only  ∼  4.6 % of fine aerosols and 15.5 % of coarse aerosols and have smaller sizes than the scattering aerosols within the same mode. Therefore, fine particles have stronger scattering than coarse ones, simultaneously reflecting the different size distributions between the absorbing and scattering aerosols. The relationships among the optical properties quantify the aerosol mixing and imply that approximately 15 and 27.5 % of the total occurrences result in dust- and black-carbon-dominating mixing aerosols, respectively, in the western YRD. Unlike the optical properties, the size distributions of aerosols in the western YRD are similar to those found at other sites over eastern China on a climatological scale, peaking at radii of 0.148 and 2.94 µm. However, further analysis reveals that the coarse-dominated particles can also lead to severe haze pollution over the YRD. Observation-based estimations indicate that both fine and coarse aerosols in the western YRD exert negative DRFs, and this is especially true for fine aerosols (−11.17 W m−2 at the top of atmosphere, TOA). A higher absorption fraction leads directly to the negative DRF being further offset for coarse aerosols (−0.33 W m−2) at the TOA. Similarly, the coarse-mode DRF contributes to only 13.3 % of the total scattering aerosols but > 33.7 % to the total absorbing aerosols. A sensitivity analysis states that aerosol DRFs are not highly sensitive to their profiles in clear-sky conditions. Most of the aerosol properties and DRFs have substantial seasonality in the western YRD. The results further reveal the contributions of each component of the different size particles to the total aerosol optical depths (AODs) and DRFs. Additionally, these results can be used to improve aerosol modelling performance and the modelling of aerosol effects in the eastern regions of China.

Citation: Zhuang, B., Wang, T., Liu, J., Che, H., Han, Y., Fu, Y., Li, S., Xie, M., Li, M., Chen, P., Chen, H., Yang, X.-Q., and Sun, J.: The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China, Atmos. Chem. Phys., 18, 1419-1436, https://doi.org/10.5194/acp-18-1419-2018, 2018.
Publications Copernicus
Short summary
Aerosols have a significant influence on climate changes. Their uncertainties could be substantially reduced if observation data were used. The properties and the DRF of fractionated aerosols in the western Yangtze River Delta are investigated based on measurements. Results reveal the characteristics of the optical properties and DRFs of different types of fractionated aerosols, which can be further used to improve aerosol modelling performance in the eastern regions of China.
Aerosols have a significant influence on climate changes. Their uncertainties could be...
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