冬季台灣附近氣流場與大氣傳送個案之數值研究

Numerical Study on the Wind Fields and Atmospheric Transports of a Typical Winter Case in Taiwan and Surrounding Area

吳清吉(Ching-Chi Wu) ； 于宜強(Yi-Chyang Yu) ； 許武榮(Wu-Ron Hsu) ； 徐光蓉(Kuang-Jung Hsu) ； 商文義(Wen-Yih Sun)

《大氣科學》 31卷1期 (2003/03) Pp. 29-54

摘要

本文利用普度區域模式(PRM)探討冬季典型天氣時，台灣複雜地形的氣流場和大氣傳送。文中所選擇1999年2月1月至2月3日的個案，是一個冬季典型東北季風，鋒面通過台灣的天氣。鋒面通過台灣時，天氣演變十分複雜，台灣附近的近地表外圍環境風場由西南風轉為北風，且持續增強；同時高層西風變強。這些特牲PRM都能準確的模擬出來。模式模擬結果也顯示台灣局部環流隨著綜觀環境風場的風向與風速的微小改變，可能大幅度的變化。因此，大氣污染物的傳送也是複雜、多變化。在强勁的東北季風下，污染物的傳播快速，在不及一天的短時間內即可由北台灣傳送至南台灣。
冬季穩定的大氣形態下，污染物不易擴散至高層。大部分的污染物集中在低層800hPa高度之下，沿著中央山脈的兩側向南迅速傳播。擴散到比較高層（約2到3公里）的大氣污染物，則迅速向東移出外海。受到背風面的合流效應和嘉南外海形成局部低壓的作用，空氣污染物容易在南台灣外海堆積。

關鍵字

普度區域模式 ； 模擬 ； 傳送

並列摘要

This paper uses the Purdue Regional Model (PRM) to study the wind fields and atmospheric transport in Taiwan and surrounding area. The case selected from February 1 to February 3,1999 is a typical winter monsoon case. During this period, the cold front passed Taiwan and the weather variations were complex. Near the surface the wind direction changed from southerly to northwesterly and the wind speed increased continuously. At the upper atmosphere the westerly wind became stronger. The PRM simulates those phenomena very well. The simulation results indicate that a small changing of the mean flow can produce a lot of changing of the local circulation. Therefore, the variations of the atmospheric transports are complex. Within one day the strong northwesterly winds bring the pollutants from the source at northern Taiwan to southern Taiwan.
In this case most pollutants are constrained in the lower atmosphere below the height of 800 hPa because of the stable atmosphere. The pollutants transport southward along the Central Mountain Range. A local low pressure forms at the ocean surface outside the coast of south Taiwan because of the confluence of the wind at leeside of mountain. The pollutants are easy to accumulate at this area.

並列關鍵字

PRM ； Simulation ； Transport