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題 名 | 大氣邊界層污染物擴散之日夜變化=Diurnal Variation of Dispersion in the Atmospheric Boundary Layer |
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作 者 | 吳清吉; 吳志宏; | 書刊名 | 大氣科學 |
卷 期 | 26:2 1998.06[民87.06] |
頁 次 | 頁181-204 |
分類號 | 354.01344563 |
關鍵詞 | 大氣邊界層; 擴散; 通量; Atmospheric boundary layer; Diffusion; Flux; |
語 文 | 中文(Chinese) |
中文摘要 | 本文以二維高階擴散模式,模擬邊界層內污染物擴散的日夜變化。擴散模式包括 濃度、濃度通量、以及濃度與溫度互變異數三個預報方程。近源點處的污染物濃度採用高斯 分佈。大氣邊界層背景場則由一維邊界層模式提供,這些背景場包括:水平風場、相當位溫 、水汽總含量,以及紊流動能。模式包含凝結、蒸發、大氣輻射和地表能量收支等物理過程 。 模擬結果顯示,夜間位於殘差層的連續點源,其煙流垂直擴散很小,大都侷限在釋放高度附 近,但是愈下風處垂直擴散的距離愈大,大致符合 Taylor 的擴散理論。由濃度收支分析可 知,污染物平流到下風處後,再由垂直擴散項分別向上、下擴展。在日間對流邊界層內,模 擬大氣擴散的結果和水槽實驗相似,即污染物濃度中心線先下降到地面,再返回高層。日出 後對流邊界層逐漸成長,當邊界層頂發展至污染源高度後,由於強烈紊流作用,使上層污染 物迅速向下混合,這種燻煙過程,模式有很好的模擬結果。 |
英文摘要 | A two-dimensional diffusion model is used to study the dispersion in the atmospheric boundary layer. This model includes three prognostic variables, which are the concentration, the concentration flux, and the covariance of temperature and concentration. A boundary layer model provides the environmental background, including the virtual potential temperature, the wind, and the turbulent kinetic energy. During the day, the plume concentration centerline descends, firstly, and intercepts the ground. Then, it rebounds to the mixed layer. But at the night, the pollutant is confined in the residual layer and rarely disperses down to the ground. At sunrise in the next day, the surface heating due to solar radiation erodes the nocturnal surface inversion layer. Therefore the mixed layer grows again. As soon as the mixed layer develops to the height of the elevated plume from the previous night, the pollutants are mixed down to the ground immediately. This process is call fumigation. This diffusion model simulates the fumigation process well. |
本系統中英文摘要資訊取自各篇刊載內容。