- 期刊
海風邊界層之發展與汙染物濃度的日變化
The Development of Sea Breeze Boundary Layer and the Diurnal Variation of the Pollutants
摘要
由於大多數的工業區以及人口集中區均位在濱海地區，而海陸風環流又是濱海地區相當突出的中尺度大氣現象，因此海陸風環流以及伴隨的海風熱力内部邊界層之發展對污染物的傳輸與擴散之影響很值得重視。本文分析觀音工業區的密集觀測資料，探討該地區海風環流之特性、海風邊界層之發展以及污染物濃度之日變化。分析之結果指出，觀音工業區在盛夏綜觀盛行風微弱時海陸風之現象相當明顯，日夜之風向反向，海風之風向約在西風到西北風之間，海風盛行時間在每天10:00到18:00之間，最強之海風風速可達5 m/sec，海風入侵時地面風速加大，陣風較強。如果南來綜觀盛行風較強烈，則海風可能隱藏在西南風之下，特徵較不明顯，只有在較強時刻始可分辨。海風邊界層的熱力結構由位溫的垂直分佈大體上可以分為三部分，最下層為混合層，除近地層外位溫在混合層中均勻分佈，中間一層位溫隨高度緩慢增加，最上層位溫隨高度增加較快，層與層之間均有穩定區存在。由風場的分析亦指出，混合層中為内流之海風，最上層之風場可代表環境風場，中間一層為海風與環境風間的轉換層，海風回流並不明顯。觀音工業區污染物地面濃度之日變化可區分為兩種型態，氮氧化物、二氧化硫及一氧化碳等化學反應活性較小之污染物，在清晨以及夜晚的濃度較高，白天的濃度則減低很多。白天由於太陽短波輻射加熱，使得地表熱量往上傳，海風入侵内流，混合層較高，污染物較易垂直擴散，地面濃度因而較低，夜晚則因為地表長波輻射冷卻，穩定層接近地面，垂直渦流擴散能力小，地面濃度因而增大。臭氧之濃度日變化則呈現另外一種特性，臭氧濃度白天正午及午後的時間有一極大值，夜間及清晨則濃度值非常低，這可能是光化反應以及上層往下擴散之結果。
並列摘要
Local flow fields, such as land and sea breezes are very important from the view point of air pollution in coastal region. An observational study is made on the boundary layer characteristics and the diurnal surface concentration variation of pollutants associated with sea breeze circulation in the Kuan-in industrial Area.It is shown that, on summer days with weakly synoptic flow, the sea breeze in the Kuan-in Industrial Area is very obvious. The sea breeze in that area is westerly or north-westerly. The vertical thermal structure of the sea breeze boundary layer can be classified into three regimes, i.e., (I) the lower mixing inflow sea breeze layer, (II) the middle transion layer and (III) the upper ambient wind layer. There are stable or inversion regions existing among these three layers.The diurnal variation of the O3 concentration has a large peak at about noon, but the peak concentration of NOх, SO2 and CO occurs in the evening and in the morning. The diurnal variation of NOх, SO2 and CO are related to the stability of the surface layer and the development of sea breeze mixing layer, while the O3 concentration is related to the daytime photochemical reaction and the turbulent downward diffusion.