Preprints
https://doi.org/10.5194/acp-2020-708
https://doi.org/10.5194/acp-2020-708
16 Nov 2020
 | 16 Nov 2020
Status: this preprint was under review for the journal ACP but the revision was not accepted.

Meteorological formation mechanism of regional transport in winter heavy air pollution events in the middle Yangtze River area, China

Yongqing Bai, Tianliang Zhao, Yue Zhou, Jie Xiong, Weiyang Hu, Yao Gu, Lin Liu, Shaofei Kong, and Huang Zheng

Abstract. Anthropogenic emission, meteorological conditions, and regional transport are the three major factors influencing heavy air pollution in China. The Hunan and Hubei provinces in the middle Yangtze River region border China's main air pollution areas, serving as the hub of regional transport of air pollutants. The meteorological formation mechanism of regional transport of air pollutants on heavy air pollution in the Hunan and Hubei provinces still remain urgent to be addressed in depth. In this study, multivariate empirical orthogonal function (MV-EOF) analysis was performed to objectively select eight typical heavy pollution events in the two provinces that occured in January 2015–2019. Based on the regional surface environment, meteorological network data, atmospheric sounding data, ERA-interim reanalysis data, and a numerical simulation experiment, this study investigated the pattern of regional transport of air pollutants in the two provinces and its mechanism of regional meteorological conditions. The results showed that transporting air pollutants mainly passed through two transport pathways, namely the Nanxiang Basin-Yunmeng Plain pathway and the Dabie Mountain's Hilly Area-Yunmeng Plain pathway, existing anomalous near-surface northerly winds in the two provinces and their upstream area accompanied by southward penetration of a shallow cold layer, all of which jointly provide a dynamic condition for regional air pollutant transport. The weak cold-air mass degenerated as it passed through the Hunan–Hubei Plain, causing warm air to accumulate in the near-surface layer of the downstream area, where winds slowed down and converged, buffering the air pollutant transport and resulting in pollutants accumulation; the near-surface atmosphere of the Hunan and Hubei provinces was a non-stagnant condition (dry intrusion of cold air, anomalous northerly winds, and positive anomalies of boundary-layer height), which is conducive to the horizontal transport of air pollutants. However, the mid-high layers, characterized by temperature inversion and the presence of a warm lid, had a stable stratification, inhibiting the diffusion of air pollutants to the upper layers; there is an obvious longitudinal vertical circulation above the Hunan–Hubei Plain, which results in the sinking and accumulation of air pollutants, thereby promoting rapid accumulation of air pollutants in the Hunan and Hubei provinces. In addition, extended empirical orthogonal function (EEOF) analysis was performed, revealing a quasi-4-d periodic oscillation pattern of air pollutants transport in the Hunan and Hubei provinces, which provides a reference for early prediction of its regional transport. The findings are of practical value in broadening the scientific understanding of the differences in the formation mechanism of heavy atmospheric pollution between the various regions of China and promoting environmental and ecological protection of the middle Yangtze Basin.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Yongqing Bai, Tianliang Zhao, Yue Zhou, Jie Xiong, Weiyang Hu, Yao Gu, Lin Liu, Shaofei Kong, and Huang Zheng
 
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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Yongqing Bai, Tianliang Zhao, Yue Zhou, Jie Xiong, Weiyang Hu, Yao Gu, Lin Liu, Shaofei Kong, and Huang Zheng
Yongqing Bai, Tianliang Zhao, Yue Zhou, Jie Xiong, Weiyang Hu, Yao Gu, Lin Liu, Shaofei Kong, and Huang Zheng

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Short summary
Heavy air pollution over central China with regional transport of PM2.5 during January of 2015-2019 were studied by using MV-EOF with multi-source observation data. It is revealed that the 3-D meteorological structure biulding a receptor region in regional transport of air pollutants over China for improving our our understanding on meteorological mechanism of regional transport of source-receptor air pollutants.
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