Comparison of three different methods for assessing in situ friction velocity: A case study from Loch Etive, Scotland
Comparison of three different methods for assessing in situ friction velocity: A case study from Loch Etive, Scotland
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DOI：
10.4319/lom.2011.9.275
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发表时间：
2011-06
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影响因子：
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通讯作者：
Tetsunori Inoue;R. Glud;H. Stahl;Andrew Hume
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作者：
Tetsunori Inoue;R. Glud;H. Stahl;Andrew Hume
对涡相关 (EC)、湍流动能 (TKE) 和惯性耗散 (ID) 三种方法进行了比较，以评估它们估计苏格兰海域摩擦速度的潜力。作为独立的评估参数，我们使用了扩散边界层 (DBL) 的同步 O2 记录，并将其与根据各自摩擦速度估计得出的理论分布进行了比较。摩擦速度是根据连续测量的湍流特性基于三种方法计算的，并且 TKE 方法估计的值明显高于其他两种方法的值。随后，计算出的摩擦速度的时间序列被用作 DBL 内 O2 分布非稳态计算的输入参数。摩擦速度是沉积物表面正上方涡流扩散率分布和 DBL 厚度的控制因素，TKE 方法的摩擦速度值得出明显更高的理论 O2 浓度，而 EC 和 ID 方法提供的结果没有显着差异。 EC 方法与 DBL 中测量的 O2 浓度的总体差异为 0.2%，TKE 方法为 9.8%，ID 方法为 0.7%。结果表明，EC 方法似乎是估计摩擦速度的最佳方法，尽管与 ID 方法没有显着差异，而 TKE 方法在约 70 m 深、相对平静的研究地点并不可靠。这些信息对于未来类似声音、峡湾和海湾的研究非常重要。
Three approaches, Eddy Correlation (EC), Turbulent Kinetic Energy (TKE), and Inertial Dissipation (ID) methods, were compared to evaluate their potential for estimation of friction velocity in a Scottish sea loch. As an independent assessment parameter, we used simultaneous O2 recordings of the diffusive boundary layer (DBL) that were compared with theoretical distribution as derived from the respective friction velocity estimates. Friction velocities were calculated based on the three approaches using continuously measured turbulent properties, and values estimated by the TKE method were significantly higher than values of the two other approaches. Time series of calculated friction velocity were subsequently employed as input parameters for nonsteady calculations of the O2 distribution within the DBL. The friction velocity is a controlling factor for the eddy diffusivity distribution immediately above the sediment surface and for the DBL thickness, and friction velocity values of the TKE method derived significantly higher theoretical O2 concentration while the EC and the ID approach provided results that were not significantly different. Overall differences from measured O2 concentration in the DBL were 0.2% for the EC method, 9.8% for the TKE method, and 0.7% for the ID method. The results reveal that the EC method appear to be the best approach for estimating friction velocities though not significantly different from the ID method, whereas the TKE method was unreliable at the ~70 m deep, relatively calm study site. This information is important for future research in similar sounds, fjords, and sea‐lochs.