A TKE-Based Framework for Studying Disturbed Atmospheric Surface Layer Flows and Application to Vertical Velocity Variance Over Canopies
A TKE-Based Framework for Studying Disturbed Atmospheric Surface Layer Flows and Application to Vertical Velocity Variance Over Canopies
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DOI：
10.1029/2018gl077853
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发表时间：
2018-07-16
影响因子：
5.2
通讯作者：
Freire, Livia S.
中科院分区：
文献类型：
--
作者：
Chamecki, Marcelo;Dias, Nelson L.;Freire, Livia S.
基于湍流动能收支方程的简化形式(简化的湍动能收支方程)，提出了一种研究扰动表层流动的方法，该方程可以用二维相空间来表示。相空间提供了一种方法来量化切变和浮力产生/破坏的相对贡献，以及当地产生和消散之间的局部不平衡。在这个框架中，Monin-Obukhov相似理论代表了一种可能的相空间降维方法。我们应用这个框架研究了亚马逊森林上空标准表层和冠层粗糙度亚层中的垂直速度变化。结果揭示了森林上空垂直速度变化行为的有趣见解，将其大小与当地TKE生产和消散之间的不平衡联系在一起。简单地说，大气最低100米处的旋风运动在将能量、气体和粒子从陆地表面输送出去和向陆地表面输送方面发挥着重要作用。这些交换构成了大气-生物圈相互作用的重要组成部分。量化和预测可用于促进这种混合的能量对于更好地了解大气和生物圈之间相互作用的程度至关重要。然而，能量含量的预测因子与地表属性密切相关，而适用于草地的理论不适用于森林或城市地区。到目前为止，每种表面类型都被单独研究过，其中一些比另一些更容易理解。在这篇文章中，我们提出了更统一地描述可用于促进垂直混合的能量的第一步，该能量在不同的表面类型中有效。我们使用在草地和亚马逊雨林上收集的观测数据来说明这个新框架的使用。需要进一步的研究才能了解它的全部能力和局限性。
We propose an approach to study disturbed surface layer flows based on a simplified form of the turbulent kinetic energy (TKE) budget equation (the reduced TKE budget), which can be represented by a two-dimensional phase space. The phase space provides a way to quantify relative contributions of shear and buoyancy production/destruction of TKE, as well as the local imbalance between local production and dissipation. In this framework, Monin-Obukhov Similarity Theory represents one possible approach to reduce the dimensionality of the phase space. We apply this framework to study the vertical velocity variance in the canonical surface layer and in the canopy roughness sublayer above the Amazon forest. Results reveal interesting insight into the behavior of the vertical velocity variance over forests, linking its magnitude to the imbalance between local production and dissipation of TKE.Plain Language Summary The whirling wind motions in the lowest 100 m of the atmosphere play an important role in transporting energy, gases, and particles away from and toward the land surface. These exchanges comprise an important part of the atmosphere-biosphere interaction. Quantifying and predicting the energy available to promote this mixing is critical to better understand the level of interactions between the atmosphere and the biosphere. However, the predictors of energy content are strongly linked to the surface properties, and theories that work over grass fields do not work over forests or urban areas. Thus far, each surface type has been studied separately and some are better understood than others. In this paper we propose the first step toward a more unified description of the energy available to promote vertical mixing valid across different surface types. We use observational data collected over a grass field and over the Amazon rainforest to illustrate the use of this new framework. Further studies will be required to understand its full capabilities and limitations.