The impact of tropical cyclones on regional ozone pollution and its future trend in the Yangtze River Delta of China

Abstract. Tropical cyclones (TCs) have a significant impact on ozone (O3) in coastal regions by affecting atmospheric circulation and meteorological conditions. This paper investigates the impact and its future changing trends in the Yangtze River Delta (YRD) region. It was found that regional O3 pollution usually occurred before TCs made landfall and after they dissipated in 2018–2022. We classified the weather patterns (SWPs) from June to September during 2018–2022 into four main categories. As pollution levels increase within the TCs weather pattern, regional temperatures rise, relative humidity decreases, and wind speeds weaken, creating a favorable environment for O3 formation and accumulation. The annual O3 concentration series is reconstructed based on changes in SWP frequency and intensity, quantifying the impact of various SWPs on future O3 variations. The analysis focuses on the number of days with the TCs weather pattern and their contribution to O3 variation. Under the SSP2-4.5 and SSP5-8.5 scenarios, future YRD O3 concentrations from June to September will increase to varying degrees relative to historical average O3 concentrations, with average increases of approximately 1.88 and 6.86 µg m−3, respectively. Under all future scenarios, the number of days with TC weather pattern increases to varying degrees, and the frequency of TCs increases significantly. The contribution of TCs weather pattern to O3 changes is increasing compared to the historical period. This shows that the intensification of climate change will intensify the impact of TCs on O3 in the YRD, and monitoring and early warning need to be strengthened.