EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2023-1393 Impact of upper-level circulation on upper troposphere and lower stratosphere ozone distribution over Northeast Asia Liao Zhiheng 1 2 Zhang Jinqiang 3 4 Pan Yubin https://orcid.org/0000-0002-3619-3188 1 2 Jia Xingcan 1 2 Ma Pengkun 1 2 Wang Qianqian 1 2 Cheng Zhigang 1 2 Dai Lindong 1 2 Quan Jiannong 1 2 Institute of Urban Meteorology, Chinese Meteorological Administration, Beijing, China Key Laboratory of Urban Meteorology, China Meteorological Administration, Beijing, China Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China 24 10 2023 2023 1 22 Copyright: © 2023 Zhiheng Liao et al. 2023 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1393/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1393/egusphere-2023-1393.pdf

Ozone (O<sub>3</sub>) in the upper troposphere and lower stratosphere (UTLS) is strongly regulated by upper-level circulation dynamics. Understanding the coupling between UTLS O<sub>3</sub> distribution and upper-level circulation dynamics is important not only to understand synoptic processes governing O<sub>3</sub> distribution and variability, but also to test the fidelity of chemistry transport models in simulating the stratosphere&ndash;troposphere exchange (STE) processes. This study presents the first systematic assessment of observationally constrained UTLS O<sub>3</sub> variability associated with upper-level circulation patterns over the Northeast Asia region. By applying the self-organized mapping (SOM) technique to 500, 250, and 100 hPa geopotential height (GPH) data, 12 circulation patterns are quantified and then used to characterize the UTLS O<sub>3</sub> distribution in the period 2000&ndash;2020 in both four-site (Beijing, Pohang, Tateno, and Sapporo) ozonesonde data and regional-scale satellite products. The underlying dynamic transport mechanism responsible for UTLS O<sub>3</sub> responses to different circulation patterns are further explored through correlation analysis between O<sub>3</sub> anomalies and transport indicators. The results indicate that although O<sub>3</sub> at almost all altitudes shows statistically significant sensitivity to circulation patterns, lower-stratospheric O<sub>3</sub> exhibits a far stronger sensitivity when compared with upper-tropospheric O<sub>3</sub>. Circulation patterns featuring the East Asian Trough (EAT) show clear enhancement of O<sub>3</sub> southwest of the trough, and the enhancement zone moves with the eastward propagation of the EAT. Circulation patterns featuring eastward-shedding vortices of the Asia Summer Monsoon Anticyclone (ASMA) show the opposite signal, in which O<sub>3</sub> concentrations are decreased, especially at Sapporo, and the negative O<sub>3</sub> anomaly zone stretches from South Japan to Sakhalin Island. Each circulation pattern is characterized by distinct transport pathways, which play a determining role in the pattern-specific UTLS O<sub>3</sub> response. Positive O<sub>3</sub> anomalies are usually associated with post-trough downward and southward transport, whereas negative O<sub>3</sub> anomalies are commonly associated with fore-trough upward and northward transport. In the lower stratosphere, the correlation between O<sub>3</sub> anomalies and transport indicators is significantly stronger than that in the upper troposphere, and the strongest correlation occurs in the lower stratosphere of Beijing.