Tropospheric ozone (O₃) is an important air pollutant with a significant impact on human health, agricultural crops, ecosystems, and global warming. In the Greater Bay Area (GBA), O₃ pollution concentration has shown an increasing trend in the last decade. It has become crucial to gain a deeper understanding of the factors contributing to this phenomenon. This study deployed a sensor network with high spatial-temporal resolution measurement of O₃ and its key precursors in mid-November 2022 during a severe O₃ episode. The spatial-temporal characteristics and contributions of local generation and regional transport were analyzed based on clustering methodology. The regional distribution and possible sources were also discussed in combination with the NAQPMS model and the HYSPLIT model. The results indicated that the O₃ episode was dominated by local generation while regional transport contributed to an average of 20 ppb in the GBA region, under the influence of sea-land winds and low-level anticyclones. Guangzhou showed the most severe O₃ pollution, with a maximum hourly concentration near 120 ppb, followed by Zhongshan, Dongguan, etc. The O₃ pollution of Hong Kong and Macau showed faster dispersion and less accumulation during the daytime. The O₃ concentrations of Huizhou and Jiangmen were the lowest, but the nighttime O₃ accumulation was close to 40 ppb during the episode. The study demonstrated ad-hoc deployment of high-density sensor networks is an effective tool to study the formation and transport of O₃ during episodic days with synoptic approaches by ad-hoc high-density sensor network measurement and combination of modeling tools.