Subgrid-scale (SGS) 2000: Analysis of Field Experimental Data to Elucidate Fundamental Physics in Parameterizations for Large-eddy Simulations

大涡模拟（LES）越来越多地用于分析与微尺度和中尺度气象学相关的尺度上的陆-气相互作用。该项目的目标是提高对亚网格尺度（SGS）运动的理解-湍流速度波动太小而无法在LES模型中解决，必须通过某种参数化来解释。方法是使用SGS2000实验收集的实验数据，该实验于2000年夏天在圣华金河谷进行。分析将采用从湍流实验室研究中产生的新想法。其中包括新的统计几何工具，用于量化SGS热通量和温度梯度矢量之间的对准，从数据中评估光谱涡流粘度和涡流扩散系数，以及研究扫描和喷射等相干结构。为了扩大可分析尺度的范围，将计划进行一项新的现场实验，该实验将结合一组热线风速计来测量湍流的细微尺度和一组声波风速计来测量较大尺度。实验设计的细节将取决于SGS2000数据的分析结果。该实地项目将与美国国家大气研究中心的大气技术部、微尺度气象部和中尺度气象部合作进行。

Large-eddy simulation (LES) is increasingly used to analyze land-atmosphere interactions at scales relevant to microscale and mesoscale meteorology. The goal of this project is to improve the understanding of subgrid-scale (SGS) motions - the turbulent velocity fluctuations too small to be resolved in LES models, which must be accounted for by some kind of parameterization. The approach is to use experimental data collected in the SGS2000 experiment, conducted in the summer of 2000 in the San Joaquin Valley. The analysis will employ novel ideas that have arisen from laboratory studies of turbulence. These include new statistical-geometrical tools to quantify alignments between SGS heat flux and temperature gradient vectors, the evaluation of spectral eddy viscosities and eddy diffusivities from the data, and the study of coherent structures such as sweeps and ejections. To extend the range of the scales that can be analyzed, a new field experiment will be planned that combines an array of hot-wire anemometers to measure the fine scales of turbulence with arrays of sonic anemometers to measure the larger scales. Details of the experiment design will depend on the outcome of the analysis of SGS2000 data. The field program will be undertaken in collaboration with the Atmospheric Technology and the Microscale and Mesoscale Meteorology Divisions of the National Center for Atmospheric Research.