Abstract
Abstract. Surface ozone has been severe during summers in the eastern parts of China, damaging human health and flora and fauna. During 2015–2018, ground-level ozone pollution increased and intensified from south to north. In North China and the Huanghuai region, the O3 concentrations were highest. Two dominant patterns of summer ozone pollution were determined, i.e., a south–north covariant pattern and a south–north differential pattern. The anomalous atmospheric circulations composited for the first pattern manifested as a zonally enhanced East Asian deep trough and as a western Pacific subtropical high, whose western ridge point shifted northward. The local hot, dry air and intense solar radiation enhanced the photochemical reactions to elevate the O3 pollution levels in North China and the Huanghuai region; however, the removal of pollutants was decreased. For the second pattern, the broad positive geopotential height anomalies at high latitudes significantly weakened cold air advection from the north, and those extending to North China resulted in locally high temperatures near the surface. In a different manner, the western Pacific subtropical high transported sufficient water vapor to the Yangtze River Delta and resulted in a locally adverse environment for the formation of surface ozone. In addition, the most dominant pattern in 2017 and 2018 was different from that in previous years, which is investigated as a new feature.
Highlights
High levels of ozone occur both in the stratosphere and at the ground level
Worldwide, polluted ozone events are more frequent and stronger in China than those that have taken place in Japan, South Korea, Europe and the United States (Lu et al, 2018). Due to their close relationship with anthropogenic emissions (Li et al, 2018), the high O3 concentrations in China are mainly observed in urban regions, such as in North China (NC, Fig. 1b), the Yangtze River Delta (YRD) and the Pearl River Delta (PRD), where rapid development has occurred in recent decades (Wang et al, 2017)
It is obvious that the data in 2014 were deficient, while the observations were broadly distributed in eastern China and continuously achieved since 2015
Summary
High levels of ozone occur both in the stratosphere and at the ground level. Stratospheric ozone forms a protective layer that shields us from the Sun’s harmful ultraviolet radiation. Worldwide, polluted ozone events are more frequent and stronger in China than those that have taken place in Japan, South Korea, Europe and the United States (Lu et al, 2018) Due to their close relationship with anthropogenic emissions (Li et al, 2018), the high O3 concentrations in China are mainly observed in urban regions, such as in North China (NC, Fig. 1b), the Yangtze River Delta (YRD) and the Pearl River Delta (PRD), where rapid development has occurred in recent decades (Wang et al, 2017). In addition to human activities and secondary aerosol processes, the impacts of atmospheric circulations and meteorological conditions must be systematically studied to improve understanding of the O3 pollution in North China. The findings of this study basically help us to understand the varying features of daily surface ozone pollution in eastern China and its relationship with large-scale atmospheric circulations
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