Ozone profiles over the industrial coast of southern Taiwan

The ozone field study on October 24 and 25, 2005 in the southern coast of Taiwan suggests that vertical ozone distributions there were highly related to the development of sea breeze and were influenced by the surrounding industrial plumes. Before the onset of sea breeze, in the midmorning, mixing depths can reach to its daily maximum (800 m in this study), and ozone is uniformly distributed throughout the mixing layer. When the sea breeze begins, the mixing layer significantly drops (400 m in this case) due to the development of thermal internal boundary layer. Subsequently, distinct ozone layers form due to the lack of mixing above the thermal internal boundary layer. Relatively ozone-rich layer up to 140 ppb was found above the sea breeze layer in this study. The ozone-rich layer may be the upwind polluted inland air mass transported to the coast and subsequently undercut by sea breeze. As well, part of the ozone in the ozone-rich layer may be depleted due to the titration of fresh NO plumes emitted from the surrounding industrial parks even at noon when photochemical activities are strong. Furthermore, the ozone can be completely depleted at nigh when photochemical production stopped and forms elevated zero-ozone air layers with a depth of several hundred meters near the coast.