A vertical profile of Ozone concentration in the atmospheric boundary layer over central Taiwan

In the central region of Taiwan, ozone episodes occur most often during aut umn. Two field experiments were conducted during the autumns of 1998 and 19 99 to analyze the vertical profile of the boundary layer and determine its effects on ozone concentration over the region. The vertical virtual potent ial temperature and wind profiles were derived from tethersonde data. The N Ox, NMHC and O-3 concentration vertical profiles were monitored up to a hei ght of 500 meters using black-covered Teflon tedler sampling bags. During the experimental periods, nighttime terrestrial long wave radiation could cause the inversion height to reach 500 meters by the following morni ng. It was shown that these types of synoptic structures suppress the verti cal diffusion of NOx, NMHC and O-3. During the daytime, measurements indica te that pollutants were well mixed in the upper portion of the mixing layer . At night, the ground level ozone concentration was on the decrease but in creased with altitude to a height of 500 m. The NOx decreased with altitude whereas the NMHC showed no significant variations.