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Volume 18, issue 7 | Copyright

Special issue: Regional transport and transformation of air pollution in...

Atmos. Chem. Phys., 18, 4897-4910, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 11 Apr 2018

Research article | 11 Apr 2018

Mixing layer height on the North China Plain and meteorological evidence of serious air pollution in southern Hebei

Xiaowan Zhu1,2, Guiqian Tang1, Jianping Guo3, Bo Hu1, Tao Song1, Lili Wang1, Jinyuan Xin1, Wenkang Gao1, Christoph Münkel4, Klaus Schäfer5, Xin Li1,6, and Yuesi Wang1 Xiaowan Zhu et al.
  • 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China
  • 3State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China
  • 4Vaisala GmbH, 22607 Hamburg, Germany
  • 5Atmospheric Science College, Chengdu University of Information Technology (CUIT), Chengdu 610225, China
  • 6Beijing Municipal Committee of China Association for Promoting Democracy, Beijing 100035, China

Abstract. To investigate the spatiotemporal variability of the mixing layer height (MLH) on the North China Plain (NCP), multi-site and long-term observations of the MLH with ceilometers at three inland stations (Beijing, BJ; Shijiazhuang, SJZ; Tianjin, TJ) and one coastal site (Qinhuangdao) were conducted from 16 October 2013 to 15 July 2015. The MLH of the inland stations in the NCP were highest in summer and lowest in winter, while the MLH on the coastal area of Bohai was lowest in summer and highest in spring. As a typical site in southern Hebei, the annual mean of the MLH at SJZ was 464±183m, which was 15.0 and 21.9% lower than that at the BJ (594±183m) and TJ (546±197m) stations, respectively. Investigation of the shear term and buoyancy term in the NCP revealed that these two parameters in southern Hebei were 2.8 times lower and 1.5 times higher than that in northern NCP within 0–1200m in winter, respectively, leading to a 1.9-fold higher frequency of the gradient Richardson number >1 in southern Hebei compared to the northern NCP. Furthermore, combined with aerosol optical depth and PM2.5 observations, we found that the pollutant column concentration contrast (1.2 times) between these two areas was far less than the near-ground PM2.5 concentration contrast (1.5 times). Through analysis of the ventilation coefficient in the NCP, the near-ground heavy pollution in southern Hebei mainly resulted from the lower MLH and wind speed. Therefore, due to the importance of unfavorable weather conditions, heavily polluting enterprises should be relocated and strong emission reduction measures should be introduced to improve the air quality in southern Hebei.

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Our study first conducted a long-term observation of mixing layer height (MLH) with high resolution on the North China Plain (NCP), analyzed the spatiotemporal variations of regional MLH, investigated the reasons for MLH differences in the NCP and revealed the meteorological reasons for heavy haze pollution in southern Hebei. The study results provide scientific suggestions for regional industrial structure readjustment and have great importance for achieving the integrated development goals.
Our study first conducted a long-term observation of mixing layer height (MLH) with high...