To understand the influences of weather and terrain on spreading ambient ozone, four areas in the air basin (the ocean, coast, basin/hill, and mountains) were examined. Data from 21 Taiwan Environmental Protection Administration (EPA) air-quality monitoring stations were analyzed. The simulated results from TAPM (version 4.0) were also analyzed. The TAPM is an atmospheric photochemical grid model that solves approximations to the fundamental fluid dynamics and scalar transport equations predicted for meteorology and pollutant concentrations. The TAPM was used in this study because it can accurately simulate a range of pollutants, especially secondary air pollutants.