Deep stratospheric intrusion events in China revealed on the ground by cosmogenic ¹⁰Be/⁷Be

Given the impact of deep stratospheric intrusion on air quality, the development of more extensive trace substances to quantify stratospheric intrusion intensity can better distinguish between stratospheric ozone pollution and anthropogenic factors. The ratio of cosmogenic beryllium-10 to beryllium-7 (¹⁰Be/⁷Be), primarily generated in the stratosphere, has the potential to identify stratospheric air masses on the ground. Here we constructed a ¹⁰Be/⁷Be time-series (July 2020 to September 2021) in rainwater and aerosols from Xi’an, China. Combining in-situ pollutants, reanalysis data, and model calculations support a stratospheric origin for increased ¹⁰Be/⁷Be and identify it as a means of quantifying intrusion intensity. It was found that anticyclones formed by the Asian summer monsoon drive a sudden increase in deep stratospheric intrusion in spring, exacerbating ozone pollution beyond China’s air quality standards. Based on the sufficiently sensitive ¹⁰Be/⁷Be, it further indicates the process of six weak upper atmosphere intrusions in Xi’an during winter.