Turbulence and Vertical Fluxes in the Stable Atmospheric Boundary Layer. Part I: A Large-Eddy Simulation Study
Turbulence and Vertical Fluxes in the Stable Atmospheric Boundary Layer. Part I: A Large-Eddy Simulation Study
复制标题
稳定大气边界层中的湍流和垂直通量。
DOI：
10.1175/jas-d-12-0167.1
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发表时间：
2013
影响因子：
3.1
通讯作者：
E. Bou‐Zeid
中科院分区：
文献类型：
--
作者：
Jing Huang;E. Bou‐Zeid
本研究旨在定量和定性地了解稳定性如何影响连续湍流稳定分层大气边界层中的传输，基于一套大涡模拟。测试案例是基于全球能源和水循环实验（GEWEX）大气边界层研究（GABLS）项目所采用的一个，但具有很大程度上扩展的稳定性范围，其中梯度理查森数（Rig）达到约1。分析主要集中在理解修改的湍流结构和动力学增加稳定性，以提高稳定的大气边界层的天气和气候模式，在本工作的第二部分中讨论的主题建模。结果表明，在准平衡状态下，稳定度的增加导致平均温度的垂直梯度增强，低空急流降低，垂直动量输送减少，垂直浮力通量增加，边界层变浅。用两点自相关方法分析相干湍流结构，发现流向速度的自相关是水平各向异性的，而垂直速度的自相关在水平面内是相对各向同性的，其积分尺度随稳定度的增加而减小。研究了稳定度对总湍动能及其收支项的影响，结果表明，作者的大涡模拟结果在不同的稳定度下与前人的实验结果吻合较好。最后，Nieuwstadt的本地缩放理论重新审视，它的结论是，高度z是不是一个相关的缩放参数，并应被替换为一个恒定的长度尺度远离表面，表明Z-少的范围开始低于先前假设的。
This study seeks to quantitatively and qualitatively understand how stability affects transport in the continuously turbulent stably stratified atmospheric boundary layer, based on a suite of large-eddy simulations. The test casesarebasedontheoneadoptedbytheGlobalEnergyandWaterCycleExperiment(GEWEX)Atmospheric Boundary Layer Study (GABLS) project, but with a largely expanded stability range where the gradient Richardson number (Rig) reaches up to around 1. The analysis is mainly focused on understanding the modification of turbulent structures and dynamics with increasing stability in order to improve the modeling of the stable atmospheric boundary layer in weather and climate models, a topic addressed in Part II of this work. It is found that at quasi equilibrium, an increase in stability results in stronger vertical gradients of the mean temperature, a lowered low-level jet, a decrease in vertical momentum transport, an increase in vertical buoyancy flux, and a shallower boundary layer. Analysis of coherent turbulent structures using two-point autocorrelation reveals that the autocorrelationof the streamwise velocity is horizontally anisotropic while the autocorrelation of the vertical velocityis relatively isotropic in the horizontal plane and its integral lengthscaledecreases as stability increases. The effects of stability on the overall turbulent kinetic energy (TKE) and its budget terms are also investigated, and it is shown that the authors’ large-eddy simulation results are in good agreement with previous experimental findings across varied stabilities. Finally, Nieuwstadt’s local-scaling theory is reexamined and it is concluded that the height z is not a relevant scaling parameter and should be replaced by a constant length scale away from the surface, indicating that the z-less range starts lower than previously assumed.