中部地區海陸風環流與高臭氧污染之相關分析

Characteristics of Sea-land Breeze Circulation and Its Influence on High Ozone Pollution in Central Taiwan

黃超群(C. C. Huang) ； 程萬里(W. L. Cheng) ； 郭冠廷(K. T. Kuo)

《東海科學》 3期 (2001/07) Pp. 57-80

摘要

中部地區背山面海，東依中央山脈，西臨台灣海峽，且位於副熱帶及熱帶氣候區的交會區，一到夏半年，由於白天日照強烈造成海、陸及山、谷間的溫差大，加上盛行季風弱，區域環流主導中部地區近地面的氣象環境，其中以海陸風環流最為明顯。為探究中部地區在海陸風盛行下的空氣品質狀況，本文分析1997-1999中部地區各氣象及空氣品質監測站的資料，結果顯示在污染事件日發生時，氣象環境大多受海陸風環流影響，春、秋二季中部地區高臭氧污染事件日發生率為51.3%。
為了解在海陸風盛行下內陸地區熱力邊界層垂直結構及污染物的垂直分布，選擇夏、秋二季不同的綜觀氣象環境下分別進行二次探空實驗，探空實驗結果顯示，在海陸風盛行日中部內陸地區的熱力邊界層大致分為三層，（Ⅰ）最下層為混合層，位溫變化大，在混合層頂常存在一逆溫層，混合深度夏季較秋季深。（Ⅱ）中間為海風與上層環境風的轉換層，此層位溫的變化小，夏季由混合層頂至約1200公尺高，秋季由混合層頂至約700公尺高。（Ⅲ）最上層為綜觀環境風，其位溫、溼度、風速及風向代表綜觀的氣象環境。臭氧濃度的擴散受混合層上的逆溫限制，最高值出現在100公尺及250公尺高。在夏季海陸風影響下，中部地區的空氣品質良好；然而在秋季海陸風影響下，中部地區的空氣品質不良。

關鍵字

中部地區 ； 臭氧 ； 海陸風環流 ； 熱力邊界層

並列摘要

The region of central Taiwan is located in the western of Central Mountain and the eastern of Taiwan Strait. Both subtropical and tropical climate influenced its climate. When summer comes, sunlight caused the difference of temperature between sea and land. The difference of temperature caused local circulation and dominates meteoric environment of central Taiwan under weak monsoon. Sea-land breeze circulation is dominant. The purpose of this paper is to analyze the effect of the sea-land breeze on ozone concentration in central Taiwan. The data of air-quality and meteoric monitoring stations of EPA and Taichung power plant for 1997-1999 were collected and analyzed in this study. The results showed that high concentrations of ozone occurred mainly under sea-land breeze. The frequency of occurrence of high ozone episodes is 51.3% in central Taiwan in spring and autumn.
For understanding the vertical structure of the boundary layer and distribution of pollutant, two experiments has been performed in two different synoptic weather. The results showed that there were three parts in the boundary layer of inland area in central Taiwan in sea-land breeze days. （Ⅰ）The lower part was mixing layer and potential temperature reduced fast with altitude. There was always an inversion in the top of mixing layer. The mixing depth in summer was thicker than in autumn. （Ⅱ）The middle part was entrainment zone of sea breeze and free atmospheric wind and potential temperature reduced slowly with altitude. The depth of entrainment zone in summer was from the top of mixing layer to 1200m and from the top of mixing layer to 700m in autumn. （Ⅲ）The higher part was free atmosphere. The higher ozone concentration was found in 100m or 250m in autumn, it meant that ozone dispersion was limited by mixing layer. During summer sea-breeze days, the air quality over Taichuang is fine, but during autumn the air quality is poor.

並列關鍵字

Central Taiwan ； Ozone ； Sea-land breeze ； Boundary layer