Influences of stratospheric intrusions to high summer surface ozone over a heavily industrialized region in northern China

The stratospheric contribution to tropospheric ozone has long been a topic of much debate over the past few decades. In this study, we leveraged multiple datasets from surface, sounding and satellite observations to reanalysis datasets, along with a global chemical transport model (Global Nested Air Quality Prediction Modelling System, GNAQPMS) to investigate the impact of a stratospheric-to-tropospheric transport (STT) event characterized by long duration and wide range in the summer on surface high ozone episodes over heavily industrialized regions in northern China. In 14-18 August 2019, the ERA5 reanalysis datasets showed a potential vorticity (PV) tongue and a deep, upper-level trough penetrate towards 35 degrees N over the North China Plain (NCP), indicating the occurrence of a stratospheric intrusion. From Atmospheric Infrared Sounder (AIRS) measurements, we found that the ozone-rich, stratospheric air mass had been injected into the lower altitudes. The GNAQPMS generally captured the featured layers, although there was a slight underestimation in the low troposphere. The averaged magnitudes of stratospheric contribution (O3S) and percentage (O3F) simulated by GNAQPMS were 3-20 mu g m(-3) and 6%-20%, respectively, while the Whole Atmosphere Community Climate Model (WACCM) indicated a higher stratospheric contribution by 3-5 mu g m(-3). Through this study, we give our opinions on the controversial topic of a more thorough understanding of the influence of natural processes apart from anthropogenic emissions, even in a heavily polluted region during summer.

Automated summary

This study investigates the impact of a stratospheric-to-tropospheric transport event on surface high ozone episodes over heavily industrialized regions in northern China during summer. The results show that the stratospheric contribution has a certain influence on surface high ozone events in the target region, which is important for understanding the influence of natural processes in heavily polluted areas during summer.