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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-1145
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Climatological study of a new air stagnation index (ASI) for China and its relationship with air pollution
Qianqian Huang, Xuhui Cai, Jian Wang, Yu Song, and Tong Zhu College of Environmental Sciences and Engineering, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Peking University, Beijing, 100871, China
Abstract. Air stagnation index (ASI) is a vital meteorological measure of the atmosphere's ability to dilute air pollutants. The original metric adopted by US National Climatic Data Center (NCDC) is found not well suitable to China, because the decouple between upper and lower atmospheric layer results in a weak link between the near surface air pollution and upper-air wind speed. Therefore, a new threshold for ASI is proposed, consisting of daily maximal ventilation in the atmospheric boundary layer, precipitation and real latent instability. In the present study, the climatological features of this newly defined ASI is investigated. It shows that the spatial distribution of the new ASI is similar to the original one; that is, annual mean stagnations occur most often in the northwest and southwest basins, i.e., Xinjiang and Sichuan basins (more than 180 days), and the least over plateaus, i.e., Qinghai–Tibet and Yunnan plateaus (less than 40 days). However, the seasonal cycle of the new ASI is changed. Stagnation days under new metric are observed to be maximal in winter and minimal in summer, which is positively correlated with air pollution index (API) during 2000–2012. The correlation between ASI and concentration of fine particulate matter (PM2.5) during January 2013 of Beijing is also investigated. It shows that the new ASI matches the day-by-day variation of PM2.5 concentration very well and is able to catch the haze episodes in that month.

Citation: Huang, Q., Cai, X., Wang, J., Song, Y., and Zhu, T.: Climatological study of a new air stagnation index (ASI) for China and its relationship with air pollution, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-1145, in review, 2018.
Qianqian Huang et al.
Qianqian Huang et al.
Qianqian Huang et al.

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Short summary
Air stagnation index (ASI) is a vital meteorological measure of the atmosphere's ability to dilute air pollutants. The original NCDC metric is not adequate to China, so we propose a new one based on daily maximal ventilation, real latent instability and precipitation. The new ASI is positively correlated with API during 2000–2012, and well tracks the day-by-day variation of PM2.5 concentration during January 2013 in Beijing.
Air stagnation index (ASI) is a vital meteorological measure of the atmosphere's ability to...
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