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梁捷宁, 张镭, 鲍婧, 赵世强, 黄建平, 张武. 黄土高原复杂地形受中尺度运动影响的稳定边界层湍流特征[J]. 大气科学, 2013, 37(1): 113-123. DOI: 10.3878/j.issn.1006-9895.2012.12004
引用本文: 梁捷宁, 张镭, 鲍婧, 赵世强, 黄建平, 张武. 黄土高原复杂地形受中尺度运动影响的稳定边界层湍流特征[J]. 大气科学, 2013, 37(1): 113-123. DOI: 10.3878/j.issn.1006-9895.2012.12004
LIANG Jiening, ZHANG Lei, BAO Jing, ZHAO Shiqiang, HUAGN Jianping, Zhang Wu. Turbulence Influenced by Mesoscale Motions in the Stable Boundary Layer over Complex Terrain of the Loess Plateau[J]. Chinese Journal of Atmospheric Sciences, 2013, 37(1): 113-123. DOI: 10.3878/j.issn.1006-9895.2012.12004
Citation: LIANG Jiening, ZHANG Lei, BAO Jing, ZHAO Shiqiang, HUAGN Jianping, Zhang Wu. Turbulence Influenced by Mesoscale Motions in the Stable Boundary Layer over Complex Terrain of the Loess Plateau[J]. Chinese Journal of Atmospheric Sciences, 2013, 37(1): 113-123. DOI: 10.3878/j.issn.1006-9895.2012.12004

黄土高原复杂地形受中尺度运动影响的稳定边界层湍流特征

Turbulence Influenced by Mesoscale Motions in the Stable Boundary Layer over Complex Terrain of the Loess Plateau

  • 摘要: 利用兰州大学半干旱气候与环境观测站(Semi-Arid Climate and Environment Observatory of Lanzhou University,简称SACOL)2008年12月观测资料,研究了稳定边界层湍流特征.使用涡动相关资料研究湍流通量时,定义湍流的平均时间τ内的中尺度运动是造成湍流统计量变化范围大的主要原因,稳定情形? τ取几十秒至几分钟.对梯度理查森数大于0.3的强稳定情形的湍流尺度分解(MRD)谱分析表明,感热通量在112.4~449.9 s存在谱隙,尺度大于谱隙的中尺度运动造成了通量观测资料离散性大,甚至有支配性影响.动量通量的谱隙在112.4~224.9 s之间.弱风时,中尺度运动的影响更大,垂直风速标准差以0.1的比率随中尺度风速变化;垂直风速标准差同广义风速表现出很好的相关性,并随着广义风速消失而消失.三维风速标准差与摩擦速度呈很好的线性关系,垂直、水平、横风风速的无量纲标准差分别为1.35、2.54、2.21.对湍流动能的研究发现,在梯度理查森数大于0.3的条件下,仍然存在连续的湍流.以湍动能为依据,分析了湍流的平稳时间长度,其长度随稳定度变化而变化,2008年12月7~11日从133.5 s变化到856.2 s,湍流平稳时间长度反映了中尺度运动的发生频率.

     

    Abstract: Turbulent characteristics in the stable boundary layer are evaluated by using data collected by the eddy covariance approach at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). The influence of mesoscale motions in the averaging time is the chief reason for the large scattering of turbulent fluxes obtained by using the eddy covariance technique. The time interval to define the turbulence ranges from several tens of seconds to several minutes. The multiresolution cospectra of the heat flux reveal a gap scale from 112.4 s to 449.9 s for strong stability when gradient Richardson number (Ri) is greater than 0.3. The motions at averaging time scales greater than the gap scale lead to large random heat flux errors and may even change the sign of heat flux cospectra. The gap scale for momentum flux occurs between 112.4 s and 224.9 s. In a weak wind regime in which the submeso velocity scale is greater than the mean flow, standard deviation of vertical velocity depends systematically on the submeso velocity scale and increases with increasing submeso velocity scale at an average rate of approximately 0.1. The standard deviation of vertical velocity correlates well with the generalized velocity scale, and approaches to zero with the generalized velocity scale vanishing. The standard deviations of w, u, and v normalized by friction velocity equal 1.35, 2.54, and 2.21 respectively. Analysis of turbulent kinetic energy reveals that persistent turbulence exists even under condition of Ri > 0.3. Stationarity time based on turbulent kinetic energy changes with stability ranged from 133.5 s to 856.2 s during December 7-11, 2008.

     

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