[Analysis of Spatial-temporal Variation and Meteorological Driving Factors of Ozone in the Taiyuan Basin from 2020 to 2023].

Abstract

To study the spatio-temporal variations and influencing factors of ozone （O₃） in the Taiyuan Basin, the main spatial distribution modes, temporal variations, and meteorological drivers of O₃ concentration were analyzed based on the day-by-day maximum O₃-8h concentration data of 11 counties in the Taiyuan Basin from 2020 to 2023 and the meteorological data for the same period using the rotated empirical orthogonal function （REOF） decomposition. The effects of valley wind circulation and regional transport on O₃ concentration in the Taiyuan Basin were further analyzed. The results indicated that the daily maximum O₃-8h 90th percentile concentration in the Taiyuan Basin exhibited fluctuating characteristics, with higher concentrations in 2021 and 2023. The variance interpretation rate of the top three modes of REOF for the concentration of O₃ in the Taiyuan Basin was 75.9%. The spatial distribution characteristics of the first mode of O₃ were "high in the north and low in the south," those of the second mode were "high in the south and low in the north," and those of the third mode were "low in the north and south and high in the middle." The high values of the time coefficients of the first two modes were mostly distributed from the middle of June to end of July. The interannual difference in the time when the high values of the time coefficients of the third mode appeared was large. According to the spatial distribution mode of O₃, the Taiyuan Basin could be divided into three parts： the northern （Taiyuan and Yuci）, southern （Fenyang, Xiaoyi, and Jiexiu）, and central regions. Temperature and wind speed had less influence on the spatial distribution of O₃ in the Taiyuan Basin, and localized transport differences caused by different wind directions were the main meteorological drivers for the formation of different spatial distribution modes of O₃. The proportion of valley wind in the Taiyuan Basin was 34.5%. During the period of valley wind control, O₃ in the basin showed a slightly lower distribution pattern in the north, south, high, and middle parts, and the average concentration was approximately 20 μg·m^-3 higher than that during non-valley wind periods. The impact of different transport trajectories on O₃ in the Taiyuan Basin varied, and pollutant transport from the southeast, south, and west could lead to an increase in O₃ pollution levels in the Taiyuan Basin.