Abstract
Ozone pollution is currently a serious issue in China. As an important source of tropospheric ozone, the stratospheric ozone has received less concern. This study uses a combination of ground-based ozone measurements, the latest ERA5 reanalysis data as well as chemistry-climate model and Lagrangian Particle Dispersion Modeling (LPDM) simulations to investigate the potential impacts of stratospheric intrusion (SI) on surface ozone pollution episodes in eastern China. Station-based observations indicate that severe ozone pollution occurred from 27 April to 28 April 2018 in eastern China, with maximal values over 140 ppbv. ERA5 meteorological and ozone data suggest that a strong horizontal-trough exists at the same time, which leads to an evident SI event and brings ozone-rich air from the stratosphere to the troposphere. Using a stratospheric ozone tracer defined by NCAR’s Community Atmosphere Model with Chemistry (CAM-Chem), we conclude that this SI event contributed about 15 ppbv (15%) to the surface ozone pollution episode during 27–28 April in eastern China. The potential impacts of SI events on surface ozone variations should be therefore considered in ozone forecast and control.
Highlights
Tropospheric ozone is an important greenhouse gas contributing to global warming [1,2] and a main pollutant harmful to human health and crop productivity [3,4]
This study investigates a severe ozone pollution episode that occurred during 28–29 April 2018 using the station-based surface ozone measurements as well as the latest ERA5 reanalysis ozone data
We find that the severe ozone pollution episode from 27 to 28 April 2018 might be related to an stratospheric intrusion (SI) event
Summary
Tropospheric ozone is an important greenhouse gas contributing to global warming [1,2] and a main pollutant harmful to human health and crop productivity [3,4]. While the anthropogenic emitted NOx decreased significantly due to government control and the VOCs emissions changed little [7,8,12], the exact reason for elevated ozone and frequently occurring ozone pollution episodes in eastern China are still not clear. Atmosphere 2020, 11, 164 deep SI events may cause a steep ozone increase near the surface and lead to ground-level ozone pollution [24,25,26,27,28] Whether such deep SI events contribute to the recently reported ozone pollution episodes in eastern China is an important question waiting to be answered. This poses a question about the potential impacts of SI events on surface ozone variations in eastern China, whereas human activities are active and heavy air pollution happens frequently [6,9,41]. The transport mechanism is analyzed using the ERA5 meteorological reanalysis data
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