亞洲地區近年來的快速發展，衍生的跨區域環境問題日益嚴重，台灣地理位置特殊，常處於亞洲大陸下風處，首當其衝，因此選擇台北地區為研究區域。春季為台北地區空氣品質不良的季節，且為東亞出流較強的季節，因此本研究目的為探討春季大台北地區同時受到本地污染及東亞出流的影響之下臭氧濃度的變化，並探討東亞出流對於臭氧濃度的貢獻及影響。 本研究結合觀測與化學模式模擬之綜合分析，由觀測資料可知：背景站萬里站的臭氧濃度維持與否和風向、風速有良好的相關性；利用TAQM（Taiwan Air Quality Model）模擬2003年春季4月13日~5月13日，此時段包含2003年春季75%的高臭氧事件日。模擬結果顯示東亞出流的垂直分布高度低於3公里，臭氧濃度約為40~60 ppb，主要由東北風傳送至台灣，此時風速較大(≧5m/s)，不利於本地污染物累積，因此不導致高臭氧事件發生，此期間東亞出流約貢獻總臭氧濃度的30~35%。高臭氧事件主要由本地排放所導致，發生於穩定的天氣系統，東亞出流的貢獻比例約為5%以下，然而，其對於高臭氧事件的發生頻率仍有相當的影響，尤其對於長時間的濃度平均影響較大。 Asian continental outflow is increasing with the rapid emission change in China and it will have impact on air quality in downwind neighboring areas. In springtime northern Taiwan is the facing direction to East Asia outflow, so that pollutants in this flow may have direct impact on ozone concentration in Taiwan. In order to understand this process, we conducted a coupled study using ozone observations in northern Taiwan and regional-scale chemical transport model simulations. In this study, we found that when the Asian continental outflow arrive in northern Taiwan, it always happened under influence of east China high pressure system with dominant wind from north-east to northern Taiwan and accompanying wind speed greater than 5 m/s. Furthermore, no high ozone episode was observed under such conditions. Using 3-D CTM simulated ozone evolution over northern Taiwan for one month in 2003 springtime. This month was chosen to cover 75% of high ozone episodes for that season. Typically, outflow concentrations reaching up wind boundary of Taiwan are in the range of 40-60 ppb. In such situation, the local ozone concentration in ground level is in the range of 40-60 ppb. It’s likely that high oxidant formation in northern Taiwan is predominantly due to local pollution.
