氣象環流對背景大氣成份傳送影響－第二部份：台灣地區氣流軌跡之氣候統計

Effect of Circulation on the Background Air Transport: Part II: The Climatology of Flow Trajectories for the Taiwan Area

林松錦(Song-Chin Lin) ； 王君賢(Chun-Shien Wang) ； 王作臺(Jough-Tai Wang) ； 胡志文(Jyh-Wen Hwu)

《大氣科學》 22卷4期 (1994/12) Pp. 565-584

摘要

本文採用等壓面軌跡線計算方法，分析1978～1982年台灣地區南、北部低層大氣（850hPa－700hPa）的氣流軌跡氣候型態，以了解台灣地區上空污染物經長程輸送可能的來源。台灣地區南、北兩地的低層大氣主要受到西南西氣流的影響；氣流在二、三月最強，到了八、九月減到最弱。八、九月時影響台灣南部的主要氣流則較偏東南東氣流。台灣地區三天的軌跡線回追分析顯示，軌跡線來源比率最高的區域大都發生在西南西區，平均傳輸距離大約2000km左右，也就是中南半島附近的區域，此區是對台灣上空作長程輸送最有利的地區。二、三月時西南氣流強盛，是台灣上空發生長程輸送最有利的兩個月份。各月份的氣流軌跡統計分析亦顯示，台灣地區南、北兩地的氣流軌跡氣候型態的確有差異。季節統計分析顯示，春、冬季時西南西氣流盛行，軌跡線大都源自西南西區，傳輸距離也較其他季節為高。在冬季時，東北方向來源的軌跡線比率在台灣南、北部的氣流軌跡統計分布均佔非常微小的比率，顯示台灣地區冬季盛行東北季風的高度並不高。而夏季時南來氣流增強，南方各區比率有明顯增加的趨勢。秋季時氣流微弱，台灣南部偏東南東方向的軌跡線增加。

關鍵字

軌跡線 ； 長程輸送

並列摘要

In order to understand the long-range transport of air pollutants reaching Taiwan area, five-years' (1978-1982) isobaric trajectories of 700hPa-850hPa level were computed to depict the climatological pattern of low-level flow trajectories for northern and southern Taiwan areas.In the vicinity of Taiwan, the low-level flow is mainly west-southwesterly. The west-southwesterly is the strongest in February and March, and becomes diminishing in August and September. In the southern Taiwan, the flow is replaced by east-southesasterly in August and September. Statistics of 3-day back-trajectories show that dominantly large percentage of trajectories are form the west-southewestern direction with average transport distance larger than 2000km. That means Indochina area is the most possible source region for long-range transport of pollutants to Taiwan area and February and March are the most favorable months for long-range transport. Monthly statistics of trajectories also indicate that the climatolgoical pattern of low-level flow trajectories is different for northern and southern Taiwan areas.As depicted by the seasonal statistics, trajectories are mainly from west-southwest direction and have larger transport distances in winter and spring seasons. In the winter season, trajectories of northeastern origin are very few, indicating that the winter northeasterly prevailing wind is very shallow. In the summer, percentages of trajectories from the southern directions have increased very much as the southerly component becomes stronger. In the autumn, the air flow is light near the Taiwan area with somewhat east-southeasterly in the southern Taiwan area.

並列關鍵字

trajectory ； long-range transport