Effect of Spatial Organization of Surface Properties on Land-Atmosphere Fluxes using a New Generation Large-Eddy Simulation

使用水文、天气和气候模式对区域动量、热量和水汽通量的预测存在相当大的误差，这与我们考虑陆地表面变化和大气不稳定的综合影响的能力有限有关。提出了一种风洞实验和大涡模拟(LES)与遥感地表条件相结合的新方法，以促进我们对地表非均匀和大气边界层之间复杂耦合的理解。首先，将建立一个框架来评估新一代大涡模拟在非均匀表面上的性能(包括在无需调谐的动态亚网格尺度模式方面的最新进展)。这将通过风洞实验以及在1997年大平原南部(SGP-97)水文实验期间获得的现场测量来实现。将特别强调研究最近开发的免调谐动态次网格尺度参数化的能力，以一致地调整与表面粗糙度和温度变化相关的流动的不均匀性和各向异性。我们还将使用合成随机替代场来研究表面属性(空气动力学粗糙度、温度和湿度)的空间组织对湍流通量的大小和分布的影响。此外，我们的结果将被用来评估传统相似理论和业务预报模式中使用的地表非均匀参数化的局限性。将提出对相似理论的物理修正，以包括地表属性的空间自相关和互相关结构的影响。拟议的研究有望提高我们模拟陆地-大气交换过程的能力，从而提高水文、天气和气候模型的准确性。尽管大型数值模式在过去几年中取得了很大的改进，但在比数值模式分辨率更小的尺度上考虑陆地表面属性(温度、粗糙度、湿度)的异质性的影响仍然是一个重大挑战。我们预计，我们的研究将提出计算效率高、物理上有吸引力的子网格参数化，以便它们可以用于业务预报模式。此外，将开发一个新的基于网络的教育工具，以利用大气边界层湍流传输的高分辨率模拟的可视化/动画的教育潜力。这一新工具将用于本科生和研究生课程以及针对高中生的外联活动。此外，两名研究生将接受培训，还将参与教育工具的拟订和实施。

0537856Porte-AgelPrediction of regional fluxes of momentum, heat and water vapor using hydrologic, weather and climate models is subject to substantial errors associated with our limited ability to account for the combined effects of land surface variability and atmospheric instability. A novel combination of wind tunnel experiments and large-eddy simulations (LES) coupled with remotely-sensed surface conditions is proposed to advance our understanding of the complex coupling between land surface heterogeneity and the atmospheric boundary layer. First, a framework will be created to evaluate the performance of the new generation LES (including recent advances in tuning-free dynamic subgrid-scale models) over heterogeneous surfaces. This will be achieved through wind tunnel experiments as well as field measurements obtained during the Southern Great Plains 1997 (SGP-97) Hydrology Experiment. Special emphasis will be placed on studying the ability of the recently developed tuning-free dynamic subgrid-scale parameterizations to consistently adjust to the flow inhomogeneity and anisotropy associated with changes in surface roughness and temperature. We will also use synthetic stochastic surrogate fields to study the effect of spatial organization of the surface properties (aerodynamic roughness, temperature and moisture) on the magnitude and distribution of the turbulent fluxes. Furthermore, our results will be used to assess the limits of conventional similarity theory and surface heterogeneity parameterizations used in operational forecast models. Physically-based modifications of similarity theory will be proposed to include the effects of the spatial autocorrelation and cross-correlation structure of surface properties.The proposed research is expected to improve our ability to model land-atmosphere exchange processes and, as a result, the accuracy of hydrologic, weather and climate models. Although substantial improvements of large-scale numerical models have been achieved over the last several years, a major challenge still remains to account for the effects of heterogeneity of land-surface properties (temperature, roughness, moisture) at scales smaller than the resolution of the numerical models. We anticipate that our research will propose sub-grid parameterizations that are computationally efficient and physically attractive such that they can be used in operational forecast models. In addition, a new web-based educational tool will be developed to take advantage of the educational potential of visualizations/animations of high-resolution simulations of turbulent transport in the atmospheric boundary layer. The new tool will be used in undergraduate and graduate courses as well as outreach activities for high school students. Furthermore, two graduate students will receive training and will also participate in the elaboration and implementation of the educational tool.