Ozonesonde, tethered balloon and instrumented ultralight aircraft were used to measure the spatial and temporal variations of air pollutant concentrations. In addition, the photolysis rate of NO2, the concentrations of HNO3 and H2O2 were measured to evaluate the effects of photochemical reactions. The field campaigns were conducted during October 25th to November 1st, 2003 and May 12th to 15th, 2004 in southern Taiwan. There were several monitoring sites with ozone concentrations exceeding 120 ppb on October 28th, 30th, 31st, and November 1st during the field campaigns and they were called the event days. In the event days, the ambient temperature and photolysis rate of NO2 were greater and daily maximum mixing heights were smaller. Sea-land breeze was significant in the October campaign: dominant northeastern wind before 10 am and prevailing northwestern wind during daytime within the surface layer. Due to the effects of dry deposition and NO titration from mobile sources, the surface ozone concentrations decreased to less than 20 ppb after 8 pm. However, the ozone concentrations might be greater than 100 ppb at higher elevation due to the effect of temperature inversion at night and the ozone residence layer persisted until the following morning. The ozone residence layer from the previous day contributed to the surface ozone concentrations in the following morning by 9.9 to 118% due to vertical transport. The radical budget method overestimated the ozone production rates due to the overestimation of HO2 radical concentrations. Therefore, the HO2 radical concentrations should be measured in the future study to evaluate the contributions from various processes. Both HNO3 and H2O2 concentrations showed significant diurnal variations with maximum concentrations at the early afternoon. The ozone sensitivity analyses based on the HNO3 and H2O2 concentrations showed that control measures for both NOx and NMHC were needed to reduce the ozone concentrations.

radiosonde,tethersonde,ozonesonde,radical budget