| 摘要: | 台灣四面環海，易引發由於比熱不同所引起的局部環流，如海陸風。沿海地區，海陸風為污染物重要傳輸因子之一。在台北地區及高屏地區高污染源之沿海地區，由於海陸風的發生對於空氣品質的影響，為本文討論之重點。 本研究探討，在海陸風發生日時，沿海地區污染物，臭氧的變化。首先依據海陸風發生成因、發生情況，以及整理許多研究所定義之海陸風，作為本研究所定義海陸風發生日。以沿海測站為中心，將垂直於平行海岸線之角度為中心，各取一百度，來作為海風及陸風風向。在日間發生陸風風向轉為海風風向，夜間發生海風風向轉為陸風風向，須同一天均發生，風向轉變須維持三小時，風速方面不得大於4 m/s，作為海陸風發生日之條件。 以觀測資料月平均24小時時序圖與測站時序資料，分析海陸風發生日與非海陸風發生日時，臭氧的變化，可由觀測資料分析中得知，在台北地區夜間發生陸風時，從內陸吹進一氧化氮將沿海地區臭氧消耗，故在夜間，海陸風發生日時的臭氧會比非海陸風發生日時低。在夏季時，由於台北地區污染範圍擴大，沿海地區亦為污染範圍內，故在台北地區夏季時，海陸風之發生未產生明顯的影響。高屏地區由於污染源位於沿海地區，故於高屏地區，海陸風未造成不同污染程度的影響。 模擬2003年海陸風發生日中，發現海風環流於日間時，會將內陸城市區域之污染物傳送至上空，經由海風環流於沿海以及海洋降下來，造成沿海地區於海風發生時，污染濃度增加。 由觀測資料得知，若污染源距離沿海區有一段距離時，內陸之污染物會經由海陸風傳輸。夜間經由陸風將內陸污染物傳送至沿海地區，與臭氧反應，使得臭氧濃度降低，而到了日間，陸風轉為海風，由模式結果可得知，海風將前一天海上之污染物吹進來，並且海風環流可將內陸污染物從上空帶至沿海近地表處，增加沿海地區污染物濃度。又由觀測資料分析結果中，發現污染源擴大至近海地區時，由於海陸風將其污染物的傳輸時，沿海地區均處於污染範圍內，故海陸風之發生於沿海地區未產生不同污染程度之影響。 Taiwan is surrounded by sea, where local circulation is easily formed. One of the typical examples is the sea-land breeze, which is also one of the most significant factors for transport pollutant in the coastland. In the area of Taipei and Kaoping in the Taiwan have high pollution source. This paper will focus on the influence of sea-land breeze on air quality over highly polluted area of Taipei and Kaoping. First of all, we would like to define “sea-land breeze day” according to the cause, the situation, and the definition in many papers of sea-land breeze. First, we draw straight a line parallel to the coastline. Then, draw a perpendicular line to it through the station. Take 50 degree, in the direction of clockwise and counterclockwise, as the direction for sea and land breeze. The conditions for sea-land breeze day include, land breeze direction switch to sea breeze direction during daytime and sea breeze direction switch to land breeze direction at night, which occur in the same day with wind direction change duration at least 3 hours long and the wind speed less than 4 m/s. If we average the daily 24 hours chart by month, the result indicates that ozone concentration of sea-land breeze days is lower than that of non sea-land breeze days among the Taipei area. In daytime, ozone concentration in sea-land breeze days is often higher then in non sea-land breeze days in Taipei area. In summer, due to the expansions of pollution area, including coastland, the influence of sea-land breeze is not obvious. However, in Kaoping area, ozone concentration in sea-land breeze days is almost the same with ozone concentration in non sea-land breeze days. In addition to analysis of observation data, we used the model to simulate the cases in 2003. In order to understand influence of sea-land breeze on air pollution in the coastland. It is shown that when sea breeze take place during daytime, the air pollution in the land will be transported to upper sky and dropped to coastland and sea with sea breeze circulation. This increased the ozone concentration in the sea-land breeze days. After analyzing the observation data, it is shown that if the pollutant is away from the coastland, the pollutant transportation will via sea-land breeze. At night, the pollutant in land is transported to the coastland via land breeze to react with ozone, which reduce the concentration of ozone. Till the daytime, land breeze will turn to sea breeze. From the modeling result, sea breeze will bring the pollutant back to land. Due to the sea breeze circulation, the pollutant will be transported from upper sky to the surface near coastland, which increase the concentration of coastland pollution. From observation result, it is also shown that the sea-land breeze will not have influence on the pollution in coastland due to the coastland is also in the range of sea-land pollutant transportation. |
