Abstract
Abstract. In the east of China, recent haze pollution has been severe and damaging. In addition to anthropogenic emissions, atmospheric circulations and local meteorological conditions were conducive factors. The number of December haze days over North China and the Huanghuai area has increased sharply since 2010 and was greatest in 2016. During 2016, the most aggressive control measures for anthropogenic emissions were implemented from 16 to 21 December, but the most severe haze pollution still occurred, covering approximately 25 % of the land area of China and lasting for 6 days. The atmospheric circulations must play critical roles in the sub-seasonal haze events. Actually, the positive phase of the East Atlantic–West Russia pattern in the middle troposphere strengthened the anomalous anti-cyclone over the NH area that confined vertical motion below. The associated southerly anomalies made the cold air and surface wind speed weaker, but enhanced the humid flow. Thus, the horizontal and vertical dispersion of atmospheric particulates was suppressed and the pollutants gathered within a narrow space. In December 2016, these key indices were strongly beneficial for haze occurrence and combined to result in the severest haze pollution. The influences of the preceding autumn sea surface temperature near the Gulf of Alaska and the subtropical eastern Pacific, October–November snow cover in western Siberia, and associated physical processes on haze pollution are also discussed.
Highlights
Because of its enormous adverse effects, haze pollution has become one of the most serious environmental problems in China, attracting considerable scientific and social attention
As a key local circulation, this anomalous anti-cyclone resulted in descending motion (Wu et al, 2017) that contributed to a reduction in the height of the planetary boundary layer (PBL)
It was hypothesized that atmospheric circulation must play a critical role
Summary
Because of its enormous adverse effects, haze pollution has become one of the most serious environmental problems in China, attracting considerable scientific and social attention. Anomalous atmospheric circulations play a key role in the formation of heavy haze pollution in winter (December–February; Chen and Wang, 2015). Other conducive weather conditions include reduced surface wind speed and enhanced humidity in the lower atmosphere (Ding et al, 2014). During 2016, haze pollution was most severe during 16–21 December, with the highest PM2.5 concentration of 1100 μg m−3 in the whole of North China and the Huanghuai area (NH, located at 30–41◦ N, 110–120◦ E) where more than 300 million people live. Understanding the role of atmospheric circulation in extreme haze pollution in December 2016 is vital, and this is analyzed in this paper. 3, we analyze the roles of global and regional atmospheric circulations in haze in December 2016.
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