3D Transport Characteristics of Ozone Pollution Affected by Tropical cyclones over the Greater Bay Area, China: Insights from a Radar Wind Profiler Network, Surface observations, and Model Simulations

Abstract. Tropical cyclones (TCs) exert a profound influence on ground-level ozone (O₃) pollution dynamics in China's Guangdong-Hong Kong-Macao Greater Bay Area (GBA). Although TC-related O₃ transport processes are well recognized, their three-dimensional characteristics remain inadequately characterized. This study provides the first comprehensive observational analysis of O₃ pollution transport mechanisms in the GBA under the influence of TC, integrating high-temporal-resolution wind profile measurements with hourly meteorological and air quality data and model simulations. The findings indicate that TC activity accounts for 39.9 % of O₃ pollution episodes in the region, with pollutants advection from northern mainland areas to coastal cities. When TCs are located at a distance of approximately 1800–2000 km, horizontal transport mechanisms dominate, facilitating the conveyance of inland ozone to coastal regions. As the proximity of the TC decreases to within 1000–1700 km, the descending air currents intensify, driving ozone from coastal areas into the boundary layer and resulting in reduced O₃ concentrations inland while they increase along the coast. In particular, when TCs approach Taiwan (less than 800 km, NE), increased vertical wind shear occurs about 34.25 % than before , particularly over coastal zones, facilitating the injection of free-atmosphere ozone into the boundary layer. This mechanism prolongs surface O₃ pollution episodes. Our findings offer critical insights for O₃ pollution mitigation strategies in the GBA and are of relevance for other globally significant bay regions susceptible to TC impacts, including Hangzhou Bay (China), Tokyo Bay (Japan), and the Bay of Bengal (India).