Impact of "blocking" structure in the troposphere on the wintertime persistent heavy air pollution in northern China

Wenyue Cai; Xiangde Xu; Xinghong Cheng; Fengying Wei; Xinfa Qiu; Wenhui Zhu

doi:10.1016/j.scitotenv.2020.140325

Impact of "blocking" structure in the troposphere on the wintertime persistent heavy air pollution in northern China

Sci Total Environ. 2020 Nov 1:741:140325. doi: 10.1016/j.scitotenv.2020.140325. Epub 2020 Jun 19.

Authors

Wenyue Cai¹, Xiangde Xu², Xinghong Cheng³, Fengying Wei³, Xinfa Qiu⁴, Wenhui Zhu⁵

Affiliations

¹ School of Geographical Science, Nanjing University of Information Science and Technology, Nanjing 210044, China; State Key Laboratory of Severe Weather (LASW), Chinese Academy of Meteorological Sciences, Beijing 100081, China; National Climate Center, China Meteorological Administration, Beijing 100081, China.
² State Key Laboratory of Severe Weather (LASW), Chinese Academy of Meteorological Sciences, Beijing 100081, China. Electronic address: xuxd@cma.gov.cn.
³ State Key Laboratory of Severe Weather (LASW), Chinese Academy of Meteorological Sciences, Beijing 100081, China.
⁴ School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China. Electronic address: xfqiu135@nuist.edu.cn.
⁵ Beijing Institute of Applied Meteorology, Beijing 100029, China.

PMID: 32886977
DOI: 10.1016/j.scitotenv.2020.140325

Abstract

In the winters of 2012-2018, a total of 25 'ultra-long' (≥6 days), wide-ranging pollution events occurred in northern China. The results showed that the atmospheric circulation pattern corresponding to 62.5% of the persistent 'most serious' and 'more serious' air pollution events in northern China were the blocking structures, and that 43.75% of the 500-hPa atmospheric circulation anomalies in the middle and high latitudes of Eurasia were 'dual-blocking', 18.75% of them were 'single-blocking'. The abnormally stable blocking situation provided a special circulation background for the occurrence and maintenance of persistent heavy air pollution in northern China. The Okhotsk blocking is significantly positively correlated with the persistent 'most serious' air pollution events. 'Stagnation' of the blocking system and its dynamic effect play an important role in regulating atmospheric environmental capacity and accelerating the accumulation of aerosols during the persistent heavy pollution episodes. Due to the synergy between the weak wind effect of the leeward slope on the eastern side of the Loess Plateau in this region and the downward airflow of the large-scale blocking system, the effect of sustained suppression of atmospheric pollutant diffusion in northern China is more significant. The downward air flow along the eastern leeward slope of the Loess Plateau is very important for accumulation of air pollutants, which is controlled by the tropospheric blocking high. In addition, the 'subsidence (temperature) inversion' effect produced by the synergy between the downward airflow of the eastern leeward slope of the Loess Plateau and the large-scale blocking system creates a continuous and stable 'warm-cover' structure in the middle of the troposphere on the eastern of the Loess Plateau; this effect strengthens the radiation effect of aerosols in the atmospheric pollutants, as well as the 'two-way feedback' mechanism between adverse meteorological conditions in the boundary layer and atmospheric pollutants.

Keywords: Dual-blocking; Northern China; Persistent ‘most-serious’ pollution events; Subsidence inversion; The Okhotsk blocking; The blocking structure.