COLLABORATIVE RESEARCH: The Role of Canopy Structure on Variability of Water and Heat Fluxes from Forested Watersheds

9903471 KatulThis研究探讨了森林流域和大气边界层（ABL）之间的水蒸气，能量和动量的交换，使用的湍流和运输的数值模拟工具的组合和以上植物冠层和最近的结果从一个全面的实地活动。 1997年10月进行的实地实验包括七个研究小组，他们在北卡罗来纳州达勒姆附近的杜克森林的松林中的七个塔上测量了水蒸气、热量、二氧化碳和动量的地表通量。 这里研究的数据集是第一个全面的实验，包括同步的速度统计和通量测量多达七个位置的树冠层的森林沿着详细的叶面积密度分布测量在空间。 为了探索和概括森林结构与观测到的热量和水汽通量之间的关系，提出了一种使用三维大涡模拟（LES）的调查。 这些模拟是第一次明确考虑在空间中的叶面积密度的变化，并采用辐射传输计划，以现实地考虑能量衰减的树叶元素。 的模拟，其中治疗的树叶作为一个多连接的多孔介质，将允许调查森林冠层的空间结构如何与能量/辐射和湍流输送动力学相互作用，从而引起所观察到的空间格局内和冠层上方的地表通量场。 一个预期的结果是了解什么样的空间变化通量可以归因于冠层结构的空间变化，冠层内的通量测量。 这项研究的结果将指导未来的实地实验，寻求估计全森林的平均通量从塔测量，并将严格评估一维冠层模型的适用范围。

9903471 KatulThis study investigates the exchange of water vapor, energy, and momentum between forested watersheds and the atmospheric boundary layer (ABL), using a combination of emerging tools in numerical simulation of turbulent flow and transport through and above plant canopies and recent result from a comprehensive field campaign. The field experiment, conducted in October of 1997, included seven research groups measuring land surface fluxes of water vapor, heat, carbon dioxide, and momentum on seven towers situated within a pine forest at Duke Forest near Durham, North Carolina. The data set studied here is the first comprehensive experiment that includes simultaneous velocity statistics and flux measurements at as many as seven locations in the canopy sublayer of a forest along with detailed leaf area density profile measurements in space. To explore and generalize the relationship between forest structure and observed heat and water vapor fluxes, an investigation using three-dimensional Large Eddy Simulations (LES) is proposed. These simulations are the first to explicitly consider variability in leaf area density in space and employ radiative transfer schemes to realistically account for energy attenuation by foliage elements. The simulations, which treat the foliage as a multiply-connected porous medium, will permit investigating how the spatial structure of forest canopies interact with energy/radiation and the turbulent transport dynamics to give rise to the observed spatial patterns in land surface flux fields within and above the canopy. An anticipated result is an understanding of what spatial variability in fluxes could be attributed to spatial variability in canopy structure for flux measurements within the canopy sublayer. The results from this study will guide future field experiments that seek to estimate forest-wide average fluxes from tower measurement and will rigorously assess the range of applicability of one-dimensional canopy models.