Hilbert方法在大氣邊界層湍流特征分析中的有效性
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國家自然科學基金項目(40333027,40205003)資助


Effectiveness of Hilbert Spectral Method in ABL Turbulent Characteristic Analysis
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    摘要:

    介紹一種新的建立在經驗模態分解(EMD)方法基礎上的非線性、非平穩數據分析技術—Hilbert分析技術,并首次將其應用于大氣邊界層(PBL)湍流數據的分析,初步探討了其在PBL湍流研究中的有效性。通過對城市與森林冠層上湍流資料的能量分布特征和統計平穩度進行分析、比較,結果表明:Hilbert譜分析能有效地對PBL湍流信號進行分析。它的邊緣譜分析能夠有效地探測PBL湍流信號的能量分布特征,統計平穩度分析也能有效地給出PBL湍流信號平穩性的定量化測量,這些將有助于建立合適的數據質量控制方法,以及對現有空氣質量與擴散模式中擴散參數的計算加以改進。文中個例分析中,城市和森林冠層上空的湍流有一定相似性,湍流混合都比較充分,但森林冠層上湍流信號的能量更多地集中在大尺度湍渦,且擾動風速的高頻部分具有更強的間歇性。對于相近高度的湍流信號來說,多數情況下,森林冠層上相同尺度的湍渦表現得比城市冠層上更不穩定,但湍渦的含能量要更低。

    Abstract:

    The Hilbert spectral analysis based on the Empirical Mode Decomposition (EMD) method for analyzing nonlinear and non stationary data is introduced and applied to the analysis of the Atmospheric Boundary Layer (ABL) turbulent signals for the first time. The effectiveness of Hilbert the spectral analysis in the research on the ABL turbulence is explored. The energy distribution characteristics and the degree of statistic stationarity of the turbulent data above the urban and forest canopies are studied. The results show the Hilbert spectral analysis is powerful and effective in the study of ABL turbulence. The Hilbert marginal spectrum is effective to get the energy distribution characteristics of ABL turbulent signals, and the analysis of the statistic stationarity is also effective to quantitatively measure the stationarity of the ABL turbulent signals. This will help establish the appropriate data quality control methods and improve the calculation of diffusion parameters of air quality and dispersion models. The case analysis shows that the turbulent flow is well mixed above both canopies. Compared with the urban canopy, the turbulent energy above the forest canopy is more concentrated in the eddies on larger scales, and the high frequency part of wind disturbance is dominated by stronger intermittency. At a given height, turbulence eddies above the forest canopy are more unstable and contain less energy than those above the urban canopy.

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李敏,蔣維楣. Hilbert方法在大氣邊界層湍流特征分析中的有效性[J].氣象科技,2013,41(1):153~159

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歷史
  • 收稿日期:2011-10-12
  • 定稿日期:2012-01-04
  • 錄用日期:
  • 在線發布日期: 2013-02-01
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