本研究應用美國環保署所發展之第二代中尺度煙陣模式（Mesopuff Ⅱ）中，關於混合層內平均風場之計算機制，結合中部地區之氣象監測站，配合本研究與中興大學環境工程學系合作，自1997至2000年所陸續施放之探空氣象資料，實際計算中部地區混合層內之平均風場。目前本研究針對中部地區之地面風場作一歸納整理與分類，進而探討風場類型與污染事件日之相關性。結果發現在所分的9種風場類型中，中部地區以第Ⅰ型（東北季風之海陸風型）發生高臭氧之機率最高，發生率高達79 ％。 本研究亦建立1996?2000年中部地區風場資料庫，運用於氣團反軌跡之運算，並結合中鼎公司的排放量資料庫（TEDs 4.2），進而求得每一網格對於受體點之污染貢獻程度。本文擬針對1997?2000年中部高污染地區（如大里、南投、竹山等）發生高臭氧事件日時，分析其臭氧前驅污染物（如NMHC、NOx等）之污染來源與各污染來源之污染貢獻量。結果發現NOx主要以點源和線源之影響最大，平均分別佔40.7％及55.7％；而NMHC則以面源之影響最大，平均佔60.7 ％。 在天氣型態與O3事件日歷年資料統計上，發現高壓迴流及熱帶低壓天氣型下事件日發生率較高，故本文亦針對這些天氣型態作逆軌跡分析，試圖尋找在此容易產生高臭氧事件的氣象條件下，其臭氧前驅物之可能來源與貢獻潛勢，以利將來作排放減量之規劃時，能提供改善臭氧等光化學煙霧污染問題之決策參考。 In this study, we used the calculation of the wind field, one element of the Mesopuff Ⅱ modeling system sponsored by the U.S. EPA in the early 1980s, to compute through the layer from the surface to the grid point mixing height. Vertical profiles of meteorological variables, measured with a tethered balloon during the period 1997-2000, were input into the calculation of the wind field. Now we create an archive of the wind fields for 1996-2000 and separate them into nine types of wind conditions with different synoptic weather patterns in central Taiwan. Measured data of ozone employed in this analysis were obtained from the monitoring stations of Taiwan Environmental Protection Administration (TEPA) over central Taiwan. The relationship between wind conditions and ozone episodes indicated that the highest frequency of occurrence of high O3 days (HODs) (defined as daily maximum O3 concentration≧80ppb for more than 2 monitoring stations) accounted for 79 % and it tends to go with Type I wind condition . Ozone is a secondary chemical pollutant, formed from NOx and VOCs (especially NMHC) in the presence of strong solar radiation. The analysis of backward trajectories and statistical analysis based on the 4 yr data (1997-2000) of NOx and NMHC could reveal features of selected ozone episodes for the most serious stations (Tali, Nantou and Nantou) in central Taiwan. Analysis results indicated that the average occurrence rates of NOx of stationary sources and mobile sources are 40.7 % and 55.7 %, and the average occurrence rate of NMHC of area sources is 60.7 %, the dominant factors contributing to the formation of the high ozone event for central Taiwan, respectively. Evaluating the backward trajectories revealed that weak westerly sea breeze is the dominant factor affecting the distribution of the high ozone event for central Taiwan. We also discuss the ozone episodes during two types of synoptic weather patterns, which is unfavorable for pollutant dispersion and leads to serious air pollution episodes. Wish these statistical data could be the reference for the policymaker to make the good decisions.
