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Published December 2021 | Supplemental Material
Journal Article Open

Large scale control of surface ozone by relative humidity observed during warm seasons in China


Rising air pollution by surface ozone (O₃) in China has induced extensive efforts to control ozone generation in major urban and industrial areas, yet mechanisms ruling the ozone production and loss are not well understood. In particular, ozone levels are strongly influenced by meteorological factors such as relative humidity, but this has been explored only in local situations, and the effect of relative humidity on ozone levels in warm seasons on a large scale in China is still unknown. Here we studied surface ozone, relative humidity, temperature, and other meteorological variables in 74 major cities in China during 2017–2018, focusing on the warm seasons in seven regions. Results show that ozone levels decrease with increasing relative humidity in all cities, with an average correlation coefficient of − 0.58, ranging from − 0.17 in Zhangjiakou to − 0.84 in Hengshui. At high relative humidity levels, above 75%, average ozone levels ranged from 44.6 to 122.5 μg m⁻³, which is lower than Chinese quality threshold of hourly average ozone level of 200 μg m⁻³. The decreases of ozone with relative humidity were more pronounced at high temperature, above 30 °C, than below 25 °C. The increases of ozone with temperature were more pronounced at low relative humidity, below 40%. Overall, our findings reveal that mechanisms ruling surface ozone levels are similar on a large scale. This is promising to design common methods of climate engineering to protect human health.

Additional Information

© The Author(s), under exclusive licence to Springer Nature Switzerland AG 2021. Received 30 December 2020; Accepted 09 July 2021; Published 22 July 2021. This work was supported in part by the Department of Science and Technology of China (No. 2016YFC0202702, 2018YFC0213506, and 2018YFC0213503), National Research Program for Key Issues in Air Pollution Control in China (No. DQGG0107), and National Natural Science Foundation of China (No. 21577126 and 41561144004). Part of this work was also supported by the "Zhejiang 1000 Talent Plan" and Research Center for Air Pollution and Health in Zhejiang University. Pengfei Li is supported by National Natural Science Foundation of China (No. 22006030), Initiation Fund for Introducing Talents of Hebei Agricultural University (412201904), and Hebei Youth Top Fund (BJ2020032).

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August 22, 2023
October 23, 2023