Observations of Coherent Turbulence Structures in the Near-Neutral Atmospheric Boundary Layer
Observations of Coherent Turbulence Structures in the Near-Neutral Atmospheric Boundary Layer
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DOI：
10.1007/s10546-010-9500-5
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发表时间：
2010-05
影响因子：
4.3
通讯作者：
Mitsuaki Horiguchi;Taiichi Hayashi;H. Hashiguchi;Yoshiki Ito;H. Ueda
中科院分区：
文献类型：
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作者：
Mitsuaki Horiguchi;Taiichi Hayashi;H. Hashiguchi;Yoshiki Ito;H. Ueda
根据日本岛崎县和重庆县的观测资料，研究了近中性大气边界层(ABL)中高雷诺数流动的湍流结构。多普勒声雷达测量了ABL地区风的垂直分布。对地面风资料时间序列进行积分小波变换，从多普勒声雷达资料中刻画出垂直范围较大(从地面到200米以上)的高速下降结构的模式。本质上，这种结构是一种特定类型的相干结构，以前在湍流边界层流动的实验中已经显示了这种结构。利用长时间尺度(S)进行小波变换，提取了ABL中的大规模高速结构。在大多数情况下，结构之间的无量纲时间间隔估计为3.0-6.2。这些结构对近地面层向下动量输送有很大贡献。对声速风速仪(20米高)测量的湍流运动进行象限分析表明，掠过运动(高速向下运动)在向下动量传递中起着重要作用。一般来说，掠过运动对动量通量的贡献与弹射运动(低速上升运动)的贡献几乎相等。这种扫掠运动的贡献与大规模的高速结构有关。
Turbulence structures of high Reynolds number flow in the near-neutral atmospheric boundary layer (ABL) are investigated based on observations at Shionomisaki and Shigaraki, Japan. A Doppler sodar measured the vertical profiles of winds in the ABL. Using the integral wavelet transform for the time series of surface wind data, the pattern of a descending high-speed structure with large vertical extent (from the surface to more than 200-m level) is depicted from the Doppler sodar data. Essentially this structure is a specific type of coherent structure that has been previously shown in experiments on turbulent boundary-layer flows. Large-scale high-speed structures in the ABL are extracted using a long time scale (240 s) for the wavelet transform. The non-dimensional interval of time between structures is evaluated as 3.0–6.2 in most cases. These structures make a large contribution to downward momentum transfer in the surface layer. Quadrant analyses of the turbulent motion measured by the sonic anemometer (20-m height) suggest that the sweep motion (high-speed downward motion) plays a substantial role in the downward momentum transfer. In general, the contribution of sweep motions to the momentum flux is nearly equal to that of ejection motions (low-speed upward motions). This contribution of sweep motions is related to the large-scale high-speed structures.