Impact of synoptic patterns and meteorological elements on the wintertime haze in the Beijing-Tianjin-Hebei region, China from 2013 to 2017

Naifang Bei; Xiaopei Li; Xuexi Tie; Linna Zhao; Jiarui Wu; Xia Li; Lang Liu; Zhenxing Shen; Guohui Li

doi:10.1016/j.scitotenv.2019.135210

Impact of synoptic patterns and meteorological elements on the wintertime haze in the Beijing-Tianjin-Hebei region, China from 2013 to 2017

Sci Total Environ. 2020 Feb 20:704:135210. doi: 10.1016/j.scitotenv.2019.135210. Epub 2019 Nov 22.

Authors

Naifang Bei¹, Xiaopei Li², Xuexi Tie³, Linna Zhao⁴, Jiarui Wu³, Xia Li³, Lang Liu³, Zhenxing Shen⁵, Guohui Li⁶

Affiliations

¹ School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China; Key Laboratory of Aerosol Chemistry and Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China.
² School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China; Jiangsu XCMG Construction Machinery Research Institute Ltd, Xuzhou, China.
³ Key Laboratory of Aerosol Chemistry and Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China.
⁴ State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing, China.
⁵ School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
⁶ Key Laboratory of Aerosol Chemistry and Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an, China. Electronic address: ligh@ieecas.cn.

PMID: 31821922
DOI: 10.1016/j.scitotenv.2019.135210

Abstract

Meteorological conditions play a key role in formation of air pollution, determining dispersion or accumulation of air pollutants. Aggressive emission mitigation measures have been taken recently in the Beijing-Tianjin-Hebei region (BTH), China, but pervasive and persistent haze still frequently engulfs this region during wintertime. Occurrence frequency of unfavorable meteorological conditions in winter is anticipated to constitute a significantly important factor in driving the heavy haze formation in BTH. Large scale synoptic patterns influencing BTH during the wintertime from 2013 to 2017 are categorized into six types, including "north-low", "southwest-trough", "southeast-high", "southeast-trough", "transition", and "inland-high" using the NCEP reanalysis data. "Southwest-trough" and "southeast-high" are defined as favorable synoptic patterns and the remaining four categories are unfavorable ones based on FLEXPART simulations. Compared to measurements of fine particulate matter (PM_2.5) in BTH, favorable synoptic conditions generally correspond to the low level or decreasing trend of PM_2.5 concentrations while under unfavorable conditions PM_2.5 concentrations are high or increasing. Occurrence of wintertime haze episodes in BTH correlates well with the evolution trend of unfavorable synoptic patterns from 2013 to 2017 although the anthropogenic emissions have substantially decreased. PM_2.5 concentrations also exhibit correlations with local meteorological elements, including winds, temperature, and relative humidity, which are ultimately steered by large scale synoptic situations. The WRF-Chem model simulations further reveal the critical role of large-scale synoptic patterns in the heavy haze formation. Overall, under unfavorable synoptic situations, emission mitigation is the best choice to improve the air quality in BTH.

Keywords: BTH; PM(2.5); Synoptic situations.