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首页> 外文期刊>Boundary-layer Meteorology >Surface Heterogeneity Effects on Regional-Scale Fluxes in the Stable Boundary Layer: Aerodynamic Roughness Length Transitions
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Surface Heterogeneity Effects on Regional-Scale Fluxes in the Stable Boundary Layer: Aerodynamic Roughness Length Transitions

机译：表面异质性对稳定边界层中区域尺度通量的影响：空气动力学粗糙度长度过渡

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摘要

The effects of abrupt streamwise transitions of the aerodynamic roughness length () on the stable atmospheric boundary layer are evaluated using a series of large-eddy simulations based on the first Global Energy and Water Cycle Experiment Atmospheric Boundary Layer intercomparison study (GABLS1). Four values spanning three orders of magnitude are used to create all possible binary distributions with each arranged into patches of characteristic length scales equal to roughly one-half, one, and two times the equivalent homogeneous boundary-layer height. The impact of the heterogeneity on mean profiles of wind speed and temperature, on surface fluxes of heat and momentum, and on internal boundary-layer dynamics are considered. It is found that transitions do not significantly alter the functional relationship between the average surface fluxes and the mean profiles of wind speed and potential temperature. Although this suggests that bulk similarity theory is applicable for modelling the stable boundary layer over heterogeneity, effective surface parameters must still be specified. Existing models that solve for effective roughness lengths of momentum and heat are evaluated and compared to values derived from the simulation data. The existing models are unable to accurately reproduce both the values of the effective aerodynamic roughness lengths and their trends as functions of patch length scale and stability. A new model for the effective aerodynamic roughness length is developed to exploit the benefits of the other models tested. It accurately accounts for the effects of the heterogeneity and stratification on the blending height and effective aerodynamic roughness length. The new model provides improved average surface fluxes when used with bulk similarity.
机译：在首次全球能源与水循环实验大气边界层比较研究（GABLS1）的基础上，使用一系列大涡模拟，评估了空气动力学粗糙度长度（）的突然沿流向过渡对稳定的大气边界层的影响。跨越三个数量级的四个值用于创建所有可能的二进制分布，每个分布成特征长度标度的补丁，这些长度分别等于等效均质边界层高度的一半，一倍和两倍。考虑了异质性对风速和温度的平均分布，对表面的热和动量通量以及对内部边界层动力学的影响。发现过渡不会明显改变平均表面通量与风速和潜在温度的平均分布之间的函数关系。尽管这表明本体相似性理论可用于对非均质性上的稳定边界层进行建模，但仍然必须指定有效的表面参数。评估解决动量和热量有效粗糙度长度的现有模型，并将其与从仿真数据得出的值进行比较。现有模型无法准确地再现有效空气动力学粗糙度长度的值及其作为斑块长度比例和稳定性的函数的趋势。开发了有效空气动力学粗糙度长度的新模型，以利用其他测试模型的优势。它准确地说明了异质性和分层对混合高度和有效空气动力学粗糙度长度的影响。当与本体相似度一起使用时，新模型提供了改进的平均表面通量。

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