ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-11-31363-2011 A parameterization of low visibilities for hazy days in the North China Plain Chen J. 1 Zhao C. S. 1 Ma N. 1 Liu P. F. 1 Göbel T. 3 Hallbauer E. 3 Deng Z. Z. 1 Ran L. 1 Xu W. Y. 1 Liang Z. 1 Liu H. J. 1 Yan P. 2 4 Zhou X. J. 1 2 Wiedensohler A. 3 Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing, China Leibniz Institute for Tropospheric Research, Leipzig, Germany now at: Meteorological Observation Centre, China Meteorological Administration, Beijing, China 30 11 2011 11 11 31363 31399 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/11/31363/2011/acpd-11-31363-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/31363/2011/acpd-11-31363-2011.pdf

Visibility degradation is a pervasive and urgent environmental problem in China. The occurrence of low visibility events is frequent in the North China Plain, where the aerosol loading is quite high and aerosols are strongly hygroscopic. A parameterization scheme for low visibility conditions on hazy days is proposed in this paper, based on visibility, relative humidity (RH), aerosol hygroscopic growth factors and particle number size distributions measured during the Haze in China (HaChi) Project. Observational results show that a high aerosol volume concentration is responsible for low visibility at RH < 90%; while for RH > 90%, decrease of visibility is mainly influenced by the increase of RH. The parameterization scheme is developed on the basis of aerosol volume concentrations and RH, taking into accounts the sensitivity of visilibity to the two factors and the availability of corresponding data. The extinction coefficients calculated with the parameterization scheme agree well with the measured values.

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