On the turbulence in the upper part of the low-level jet: An experimental and numerical study
On the turbulence in the upper part of the low-level jet: An experimental and numerical study
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DOI：
10.1007/s10546-005-0608-y
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发表时间：
2006-02-01
影响因子：
4.3
通讯作者：
Cuxart, J.
中科院分区：
文献类型：
--
作者：
Conangla, L.;Cuxart, J.
分析了在西班牙“巴哈-阿莫斯费拉中心”观测到的低空急流(LLJ)的特征，重点分析了低空急流上部产生的湍流，这一特征仍有待彻底了解。在西班牙(Sables)1998年的稳定边界层实验期间，密集地进行了捕获气球探测，它们的分析突出了急流的风和温度结构的主要特征，从而形成了一种复合廓线。有迹象表明，湍流在风的最大值水平有一个最小值，在高度为低空急流最大值的两到三倍的层中，湍流升高，但在这些高度没有湍流的直接测量。2001年9月，对同一地点的一座100米高的塔楼进行了重新测量，以提供高达地面96.6米的湍流测量。选取了2002年9月至2003年6月期间发生在该高度以下的所有低空急流，并在低空急流上方发现了显著的湍流。为了进一步研究高空湍流的产生，采用单柱湍流动能模型进行了数值模拟。结果与测量结果吻合较好，表明在低空急流上方有明显切变和弱稳定层结的层内，条件有利于湍流的发展。
The characteristics of low-level jets (LLJ) observed at the "Centro de Investigacion de la Baja Atmosfera" (CIBA) site in Spain are analysed, focussing on the turbulence generated in the upper part of the jet, a feature that is still to be thoroughly understood. During the Stable Boundary Layer Experiment in Spain (SABLES) 1998, captive balloon soundings were taken intensively, and their analyses have highlighted the main characteristics of the jet's wind and temperature structure, leading to a composite profile. There are indications that the turbulence has a minimum at the level of the wind maximum, with elevated turbulence in a layer at a height between two and three times that of the LLJ maximum, but no direct measurements of turbulence were available at these heights. In September 2001, a 100-m tower at the same site was re-instrumented to give turbulence measurements up to 96.6 m above ground level. All occurrences of LLJ below this height between September 2002 and June 2003 have been selected and significant turbulence above the LLJ has been found. Simulations with a single-column turbulence kinetic energy model have been made in order to further investigate the generation of elevated turbulence. The results correlate well with the measurements, showing that in the layer above the LLJ, where there is significant shear and weakly stable stratification, conditions are conducive to the development of turbulence.