Probing eddy size and its effective mixing length in stably stratified roughness sublayer flows
Probing eddy size and its effective mixing length in stably stratified roughness sublayer flows
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稳定分层粗糙度亚层流中涡流尺寸及其有效混合长度的探测
DOI：
10.1002/qj.4386
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发表时间：
2022
影响因子：
8.9
通讯作者：
Katul, Gabriel
中科院分区：
文献类型：
--
作者：
Peltola, Olli;Aurela, Mika;Launiainen, Samuli;Katul, Gabriel
稳定分层糙率底层流是普遍存在的，但仍然难以表示在模型中，并解释使用现场实验。在这里，从森林地面到6.5倍的冠层高度的连续高频位温分布，采用分布式温度传感（DEM）将涡动拓扑与粗糙度子层稳定性校正函数以及冠层内和冠层上方空气层之间的耦合联系起来。实验在两个林分进行分类为流体动力学稀疏和密集。使用一种新的条件采样方法，从观察到的剖面中推导出涡尺寸（长度尺度）和有效混合长度的近连续剖面。该方法利用从静态稳定的背景状态的潜在的温度等值线波动。通过观测到的涡流的位温的传输被假定为守恒的（绝热运动），并且我们假定涡流和周围背景之间的不可逆热交换沿着沿着涡流的（垂直）外围发生。这个假设类似于普朗特的混合长度概念，其中动量被快速垂直传输，然后与局部平均速度梯度平衡。从观测到的配置文件中出现的背景分层，地面以上的高度，和冠层特征的长度尺度的一个明显的依赖。这些研究结果的影响（1）莫宁-奥布霍夫相似性的失败粗糙子层和（2）以上冠层流耦合到森林地面进行了检查。研究结果有实际应用方面的分析类似的CO2数据集与所提出的方法，粗糙度子层流动建模，并解释夜间涡动协方差测量高大的森林树冠。
Stably stratified roughness sublayer flows are ubiquitous yet remain difficult to represent in models and to interpret using field experiments. Here, continuous high‐frequency potential temperature profiles from the forest floor up to 6.5 times the canopy height observed with distributed temperature sensing (DTS) are used to link eddy topology to roughness sublayer stability correction functions and coupling between air layers within and above the canopy. The experiments are conducted at two forest stands classified as hydrodynamically sparse and dense. Near‐continuous profiles of eddy sizes (length scales) and effective mixing lengths for heat are derived from the observed profiles using a novel conditional sampling approach. The approach utilizes potential temperature isoline fluctuations from a statically stable background state. The transport of potential temperature by an observed eddy is assumed to be conserved (adiabatic movement) and we assume that irreversible heat exchange between the eddy and the surrounding background occurs along the (vertical) periphery of the eddy. This assumption is analogous to Prandtl's mixing‐length concept, where momentum is transported rapidly vertically and then equilibrated with the local mean velocity gradient. A distinct dependence of the derived length scales on background stratification, height above ground, and canopy characteristics emerges from the observed profiles. Implications of these findings for (1) the failure of Monin–Obukhov similarity in the roughness sublayer and (2) above‐canopy flow coupling to the forest floor are examined. The findings have practical applications in terms of analysing similar DTS data sets with the proposed approach, modelling roughness sublayer flows, and interpreting nocturnal eddy covariance measurements above tall forested canopies.
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DOI：
--
发表时间：
1994
期刊：
影响因子：
--
作者：
A. Jacobs;J. H. Boxel;R. El
通讯作者：
R. El
通量分布与粗糙度子层校正的关系
影响因子：
8.9
作者：
J. Arnqvist;Hans Bergström
通讯作者：
Hans Bergström
影响因子：
6.8
作者：
R. Abolafia‐Rosenzweig;C. He;S. Burns;Fei Chen
通讯作者：
R. Abolafia‐Rosenzweig;C. He;S. Burns;Fei Chen
影响因子：
4.3
作者：
Cava, D;Katul, GG;Giostra, U
通讯作者：
Giostra, U
影响因子：
4.3
作者：
I. Harman;J. Finnigan
通讯作者：
I. Harman;J. Finnigan