| 用连续子波变换提取城市冠层大气湍流的相干结构 |
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| 引用本文： | 陈炯,郑永光,胡非.用连续子波变换提取城市冠层大气湍流的相干结构[J].大气科学,2003,27(2):182-190. |
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| 作者姓名： | 陈炯 郑永光 胡非 |
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| 作者单位： | 1.中国科学院大气物理研究所大气边界层物理和大气化学国家重点实验室,北京,100029;中国气象局国家气象中心,北京,100081 |
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| 基金项目： | 国家自然科学基金资助项目49975008和中国科学院知识创新工程项目KZCX2-204共同资助 |
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| 摘 要： | 切变湍流的相干结构是湍流研究中的重大发现,它表明湍流在表面上看来不规则运动中具有可检测的有序运动,这种相干结构在切变湍流的脉动生成和发展中起着主宰作用.因此识别和提取相干结构对于认识和研究湍流是非常重要的.用数字滤波法将包含相干结构的大尺度信号提取出来以后,再用子波分析,根据子波能量极大值的判别方法,分别确定出大气湍流三个方向上的速度脉动信号相干结构的频率或时间尺度,然后由确定尺度上的连续子波反演公式,提取出大气湍流三个方向上的速度脉动信号相干结构所对应的波形.
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| 关 键 词： | 大气湍流 相干结构 子波分析 |
Isolating the Coherent Structure in Atmospheric Turbulence in the Rough Urban Canopy Layer by Using Continuous Wavelet Transform |
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| Chen Jiong,Zheng Yongguang and Hu Fei.Isolating the Coherent Structure in Atmospheric Turbulence in the Rough Urban Canopy Layer by Using Continuous Wavelet Transform[J].Chinese Journal of Atmospheric Sciences,2003,27(2):182-190. |
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| Authors: | Chen Jiong Zheng Yongguang and Hu Fei |
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| Abstract: | Presence of coherent structures in turbulent shear flows is a great finding in turbulence research, which shows the orderly flows in turbulence seeming fully random. These coherent structures play an important dynamical role in fluctuation's generating and developing. It is necessary to detect and isolate the coherent structures from the turbulence signals. We have decomposed atmospheric turbulence signal into large scale eddies which include coherent structures and small eddies which is stochastic by using Fourier digital filtering. In this paper, wavelet energy computed for the three components of the velocity fluctuations appears to have local maximum values at certain time scales, which corresponds to the scales or frequencies of coherent structures. Then we extract the coherent signals from the large scale vortex at this scale by inverse wavelet transform formula. This method provides an objective technique for examining the turbulence signal associated with coherent structures in atmospheric boundary layer. |
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| Keywords: | atmospheric turbulence coherent structure wavelet analysis |
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