• 作者： 張能復
• 作者服務機構： 中央研究院物理研究所
• 中文摘要： 本文主要討論應用紊流高階收合模式研究對流性大氣邊界層的變化。紊流收合模式的主要假設為紊流回復等向性效應(Rotta [14]）、紊流動能滯耗效應(Kolmogoroff, [8]），及第三階與第二階紊流統計量間之逆梯度傳遞性效應。 從模式模擬之紊流邊界層各種總集平均量與實驗觀測數據比較相當一致。進一步的檢討模擬結果可以發現，對流性大氣邊界層可以定性分成三層：近地層、混合層與紊流逆溫層。在紊流逆溫層以下之總集平均速度與位溫變化呈高度之相似性，而地轉風切變對該種相似性沒有影響。本文另以定性理論分析，發現地轉風切變屬於長時間（在中緯度為3～6小時）之效應，而紊流對流混合作用屬於短時間之效應（數分鐘）。模式研究結果印證這種推論。在整個對流邊界層與自由大氣層接合過程中，紊流逆溫層之熱力與動力作用不可忽略。
• 英文摘要： In this study，the continuous evolution of a convective planetary boundary layer (PBL) is simulatedby turbulence higher-order-closure model. The closure assumptions include the return-to-isotropy effectproposed by Rotta [14], the universal theory about turbulence dissipation by Kolmogoroff [8], and thedown-the-gradient transport analogy relating third-moment quantities to second-moment quantities. Statistics of turbulence in a convective PBL simulated by model are compared with experimentaldata. The detailed turbulence structure predicted by model is reasonably well. As inferred from the simulation study, a convective PBL can be conceived as comprising three layers:the surface layer, the well-mixed layer, and the turbulent inversion layer. Below the turbulent inversionlayer, ensemble mean profiles of a convective PBL reveal similarity, regardless of the baroclinic geostrophicshear. This is due to the existence of two distinct time scales associated with geostrophic forcing and con-vective turbulence mixing. The geostrophic shear is not effective in changing the ensemble mean profiles,because of its long-time scale process compared to convective turbulent mixing. Finally, the turbulentinversion layer serves as the matching layer which connects the mixing layer from below to the free atmos-phere above, both dynamically and thermodynamically.
• 中文關鍵字： turbulence closure model; convective; planetary boundary layer
• 英文關鍵字： --