Influence of Wind Flows on Surface O[sub.3] Variation over a Coastal Province in Southeast China

• Published in: Atmosphere 2024-02, Vol.15 (3)
• Main Authors: Shen, Yukun, Liu, Jane, Chen, Zhixiong, Yang, Mengmiao, Shu, Lei, Gai, Chende, Jiang, Yongcheng
• Format: Article
• Language: English
• Subjects: Air pollution; Air quality; Composition; Environmental aspects; Ozone; Winds
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos15030262

Surface ozone (O[sub.3] ) is influenced not only by anthropogenic emissions but also by meteorological factors, with wind direction being one of the most overlooked factors. Here, we combine the observational data of both O[sub.3] and wind flow to compare the variation in surface O[sub.3] with wind direction between coastal and inland regions of Fujian, a province in the southeast coast of China with complicated topography. We further conduct a numerical simulation using a global chemical transport model, GEOS-Chem, to interpret the observational results, explore the linkages between these O[sub.3] variations and wind flows, and identify the dominant processes for the occurrence of high O[sub.3] that varies with wind flows. The results from the observations over 2015–2021 suggest that, over coastal regions, surface O[sub.3] concentrations show a strong dependence on wind flow changes. On average, during the daytime, when southeasterly winds prevail, the mean of O[sub.3] concentrations reaches 83.5 μg/m[sup.3] , which is 5.0 μg/m[sup.3] higher than its baseline values (the mean O[sub.3] concentrations), while the northwesterly winds tend to reduce surface O[sub.3] by 6.4 μg/m[sup.3] . The positive O[sub.3] anomalies with southeasterly wind are higher in the autumn and summer than in the spring and winter. During the nighttime, the onshore northeasterly winds are associated with enhanced O[sub.3] levels, likely due to the airmass containing less NO[sub.2] , alleviating the titration effects. Over inland regions, however, surface O[sub.3] variations are less sensitive to wind flow changes. The GEOS-Chem simulations show that the prevailing southeasterly and southwesterly winds lead to the positive anomaly of chemical reactions of O[sub.3] over coastal regions, suggesting enhanced photochemical production rates. Furthermore, southeasterly winds also aid in transporting more O[sub.3] from the outer regions into the coastal regions of Fujian, which jointly results in elevated surface O[sub.3] when southeasterly winds dominates. When affected by wind flows in different directions, the chemical reaction and transport in the inland regions do not exhibit significant differences regarding their impact on O[sub.3] . This could be one of the reasons for the difference in O[sub.3] distribution between coastal and inland regions. This study could help to deepen our understanding of O[sub.3] pollution and aid in providing an effective warning of high-O[sub.3] episodes.