Collaborative Research: The Role of Canopy Structure on Variability of Water and Heat Fluxes from Forested Watersheds

9902957 Albertson这项研究利用数值模拟中的新兴工具和植物冠层上方的湍流传输的最新结果和最新的综合野外研究结果，研究了森林流域和大气边界层(ABL)之间的水汽、能量和动量的交换。1997年10月进行的野外实验包括七个研究小组，在北卡罗来纳州达勒姆附近杜克森林的七座塔上测量了水蒸气、热量、二氧化碳和动量的陆地表面通量。这里研究的数据集是第一个全面的实验，它包括在森林冠层中多达七个位置的同时速度统计和通量测量，以及空间中详细的叶面积密度剖面测量。为了探索和推广森林结构与观测到的热量和水汽通量之间的关系，提出了一种基于三维大涡模拟(LES)的研究方法。这些模拟首次明确考虑了叶面积密度在空间中的可变性，并使用辐射传输方案来真实地解释叶元素的能量衰减。这些模拟将树叶视为多连通的多孔介质，将允许研究森林树冠的空间结构如何与能量/辐射相互作用，以及湍流传输动力学如何产生树冠内和树冠上方陆地表面通量场的观测空间模式。一个预期的结果是理解在冠层亚层内通量测量的冠层结构的空间变异性可以归因于通量的什么空间变异性。这项研究的结果将指导未来的野外实验，这些实验试图从塔式测量中估计全森林范围内的平均通量，并将严格评估一维树冠模型的适用范围。

9902957AlbertsonThis 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.