海面微结构图像数据处理算法与系统集成
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摘要
海面微尺度波主要是指毛细波和毛细重力波,通常骑行在长重力波上,它是影响海-气界面动量、热量和物质交换的重要因素。国家海洋局第一海洋研究所在国家863项目的支持下研制出基于颜色编码原理的“海面微结构光学测量装置”,并进行了大型动力实验水槽和海洋现场实验,获取了大量的海面微结构图像数据。
本文利用“微结构光学测量装置”获取的图像数据开展了数据处理方法研究,给出了微结构图像波面斜率校准、斜率波数谱提取和频率谱提取方法。首先进行了海面微结构图像的波面斜率校准研究,分析了标准定标小球两次折射的影响,给出了利用净水面图像提取微尺度波斜率时系统误差修正方法。在此基础上,指出标准小球定标过程中噪声点对定标结果的影响不可忽视,实际处理时必须将噪声点滤除,并给出滤除阈值。其次,利用校准后的斜率计算得到微尺度波的有效波高,进而计算微尺度波的斜率波数谱和频率谱。但由于海面微结构图像大小有限,这样长重力波被有限截断,导致在谱分析时出现频率混叠,即Gibbs现象。因此本文引入二维EMD(经验模态分解)方法滤除造成频率混叠的长重力波,然后进行傅立叶变换,得到海面微尺度波谱,进一步处理得到斜率波数谱和频率谱。斜率波数谱提取结果表明:波数在约小于37rad/cm时,波数谱以波数的-3次方下降;在波数约为3rad/cm时,出现了“dip”现象,此现象与国外已有结果一致。频率谱提取结果表明:频率谱按照频率的幂指数率下降,但利用实验计算结果和半经验模式结果的幂指数的值有差异。再次,分析了微尺度波斜率波数谱以及频率谱对风速的依赖性,得到了共同的变化特征:谱值随风速的增加而增加,但增加的幅度随风速增加而减小。最后,将上述算法集成为“海面局部微尺度图像数据处理系统”。
The micro-scale waves of the sea surface mainly refer to the capillary and capillary-gravity surface waves, which often ride on the long gravity surface waves and become an important factor in momentum, energy and mass exchanges at the air-sea interface. A sea surface microstructure optical measuring device based on a color-coded principle was established by the First Institute of Oceanography with the fund of‘863’project, and the corresponding experiment were carried out in a laboratory wind wave tank and in the water offshore. A mass of microstructure image data were captured from the experiments.
Data processing method is developed using the data captured by“microstructure optical measuring apparatus”. First of all, the calibration of microstructure image wave gradient is studied, and the deviation about wave surface gradient between the calibration and the pure water surface when the rays of light are refracted twice is put forward. Furthermore, the amount of sampling noise pelses in the process of calibration influences the calibration precision obviously, so the noise pelses have to be taken out in practice. Second, significant wave height is calculated using the calibrated gradient, and the total slope wave number spectrum and the frequency spectrum are obtained. But because of the finite area of measurements, the long gravity waves are cut off within a period and the phenomenon of frequency aliasing will be appeared. This phenomenon is called Gibbs phenomenon. Therefore, two-dimensional Empirical Mode Decomposition algorithm was used in this dissertation to obtain the capillary and capillary gravity wave information. And then the wave number-frequency spectrum of the micro-scale wave is deduced from the Fourier transform. By integrating the wave number-frequency spectrum over all possible frequencies, we find the wave number spectrum, and obtain the frequency spectrum similarly. The consequence of slope wave number spectrum indicates that there is a -3 power in the spectra when the wave number is less than 37 rad/cm, and there is a dip when the wave number is about 3 rad/cm. This conclusion agrees well with accepted results; the consequence of slope wave number spectrum indicate that frequency decline with power exponent, but the value of the exponent is different between the experiment and semi-empirical value. Third, the dependence of microwave slope wave number spectrum and frequency spectrum on the wind speed is analyzed, and the similarly character about them is obtained as: the spectrum value increase with the wind speed, but the gradient decrease. At last, we integrate the correlation algorithm about the data processing into“Local Sea Surface Microstructure Image Data Processing System”.
本文利用“微结构光学测量装置”获取的图像数据开展了数据处理方法研究,给出了微结构图像波面斜率校准、斜率波数谱提取和频率谱提取方法。首先进行了海面微结构图像的波面斜率校准研究,分析了标准定标小球两次折射的影响,给出了利用净水面图像提取微尺度波斜率时系统误差修正方法。在此基础上,指出标准小球定标过程中噪声点对定标结果的影响不可忽视,实际处理时必须将噪声点滤除,并给出滤除阈值。其次,利用校准后的斜率计算得到微尺度波的有效波高,进而计算微尺度波的斜率波数谱和频率谱。但由于海面微结构图像大小有限,这样长重力波被有限截断,导致在谱分析时出现频率混叠,即Gibbs现象。因此本文引入二维EMD(经验模态分解)方法滤除造成频率混叠的长重力波,然后进行傅立叶变换,得到海面微尺度波谱,进一步处理得到斜率波数谱和频率谱。斜率波数谱提取结果表明:波数在约小于37rad/cm时,波数谱以波数的-3次方下降;在波数约为3rad/cm时,出现了“dip”现象,此现象与国外已有结果一致。频率谱提取结果表明:频率谱按照频率的幂指数率下降,但利用实验计算结果和半经验模式结果的幂指数的值有差异。再次,分析了微尺度波斜率波数谱以及频率谱对风速的依赖性,得到了共同的变化特征:谱值随风速的增加而增加,但增加的幅度随风速增加而减小。最后,将上述算法集成为“海面局部微尺度图像数据处理系统”。
The micro-scale waves of the sea surface mainly refer to the capillary and capillary-gravity surface waves, which often ride on the long gravity surface waves and become an important factor in momentum, energy and mass exchanges at the air-sea interface. A sea surface microstructure optical measuring device based on a color-coded principle was established by the First Institute of Oceanography with the fund of‘863’project, and the corresponding experiment were carried out in a laboratory wind wave tank and in the water offshore. A mass of microstructure image data were captured from the experiments.
Data processing method is developed using the data captured by“microstructure optical measuring apparatus”. First of all, the calibration of microstructure image wave gradient is studied, and the deviation about wave surface gradient between the calibration and the pure water surface when the rays of light are refracted twice is put forward. Furthermore, the amount of sampling noise pelses in the process of calibration influences the calibration precision obviously, so the noise pelses have to be taken out in practice. Second, significant wave height is calculated using the calibrated gradient, and the total slope wave number spectrum and the frequency spectrum are obtained. But because of the finite area of measurements, the long gravity waves are cut off within a period and the phenomenon of frequency aliasing will be appeared. This phenomenon is called Gibbs phenomenon. Therefore, two-dimensional Empirical Mode Decomposition algorithm was used in this dissertation to obtain the capillary and capillary gravity wave information. And then the wave number-frequency spectrum of the micro-scale wave is deduced from the Fourier transform. By integrating the wave number-frequency spectrum over all possible frequencies, we find the wave number spectrum, and obtain the frequency spectrum similarly. The consequence of slope wave number spectrum indicates that there is a -3 power in the spectra when the wave number is less than 37 rad/cm, and there is a dip when the wave number is about 3 rad/cm. This conclusion agrees well with accepted results; the consequence of slope wave number spectrum indicate that frequency decline with power exponent, but the value of the exponent is different between the experiment and semi-empirical value. Third, the dependence of microwave slope wave number spectrum and frequency spectrum on the wind speed is analyzed, and the similarly character about them is obtained as: the spectrum value increase with the wind speed, but the gradient decrease. At last, we integrate the correlation algorithm about the data processing into“Local Sea Surface Microstructure Image Data Processing System”.
引文
[1] Banner M.L. et al. Wave number spectra of short gravity waves, J. Fluid Mech,1989, 198:321-344
[2] Bernd J, Klaus S.Riemer. Two-Dimensional wave number spectra of small-scale water surface waves. Journal of Geophysical Research, 1990, 95(C7): 11531-11546
[3] Charles Cox et al. Statistics of the sea surface derived from sun glitter. Journal of Marine Research, 1954,13: 198-227
[4] Charles, Cox. S. Measurement of slopes of high-frequency wind waves. J.Marine Res., 1958, 16(3): 199-225
[5] Corless R. M, Gonnet G.H, D.E. G. Hare. On the Lambert W Function. Advances in Computational Mathematics,1996,5:329-359
[6] Cos.S, Munk. W. Statistics of the sea surface derived from sun glitter. J.Mar.Res. 1954a, 13:198-227
[7] Cox.S, Munk.W. Measurements of the roughness of the sea surface from photographs of the sun’s glitter. J.Optical Soc.Amer.1954b, 44:838-850
[8] Cox.S, Palm et al. Laser probe for measuring 2-D wave slope spectra of ocean capillary waves. Applied Optics, 1977, 16(4): 1074-1081
[9] Cox.S. Measurement of slopes of high-frequency wind waves. J Marine Res, 1958, 16(3): 198-227
[10] Crapper,G.D. An exact solution for progressive capillary wavrs of arbitrary amplitude. J. Fluid Mech.1957,2(6):532-540
[11] Michael S, Longuet-Higgins. Parasitic capillary waves: a direct calculation. J.Fluid Mech.,1995,301:79-107
[12] Norden E. Huang et al. The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis, Proc. R. Soc. Lond. A , 1998, 454: 903-995
[13] Paul A. Hwang et al. A study of the wavenumber spectra of short water waves in the ocean, Journal of Physical Oceanography,1995, 26:1266-1283
[14] Phillips O M. The Dynamics of the Upper Ocean, Cambridge University Press, London, 1980
[15] Sun H Q, Qiu D H, Shen Y M et al. Wave measurement based on light refraction. Acta Oceanologica Sinica , 2004, 23 (2): 359-366
[16] Tetsu Hara et al. Frequency-wavenumber spectrum of wind-generated gravity-capillary waves. Joutnal of Geophisical Research, 1997, 102(C1):1061-1072
[17] Tetsu Hara et al. In situ measurements of capillary-gravity wave spectra using a scanning laser slope gauge and microwave radars. 1994, Joutnal of Geophisical Research, 99(C6): 12593-12602
[18] Wang Y F, Guan S, Huang W M, Zhang J, Ding YY. The short wave observation using the optical instrument for detecting microstructure of sea surface wave. SPIE Proceedings–Ocean Remote Sensing and Applications,2003, 4892:462-472
[19] Yoshiaki Toba. Local Balance in the Air-sea Boundary Processes I. On the Process of Wind Waves. Journal of the Oceanographical Society of Japan, 1972, 28: 109-121
[20] Yoshiaki Toba. Local Balance in the Air-sea Boundary Processes III. On the Spectrum of Wind Waves. Journal of the Oceanographical Society of Japan, 1973, 29: 209-220
[21] Zhang X & Charles S. Cox. Measuring the two-dimensional structure of a wavy water surface optically: A surface gradient detector, Experiments in Fluids ,1994, 17:225-237
[22] Zhang X, Charles S. Cox. Measuring the two-dimensional structure of a wavy water surface optically: a surface gradient detector. Experiments in Fluids, 1994, 17: 225-237
[23] Zhang X. Capillary-gravity and capillary waves generated in a wind wave tank: observations and theories. J Fluid Mech, 1995, 289: 51-82
[24] Zhang X. Observations on wave forms of capillary and gravity-capillary waves, Eur.J. Mech. B/Fluids, 1999, 374-388
[25] Zhang X. Wavenumber spectrum of short wind waves: an application of two-dimensional slepian windows to spectral estimation, Journal of Atmospheric and Oceanic Technology, 1994, 11:489-505
[26] Zhang X., J. Klinke, B. J?hne. A study of advection of short wind waves by long waves from surface slope images. The Fourth Air-Sea InterfaceSymposium, Sydney, Australia, 1999
[27] Zhang,X. A study of capillary and capillary-gravity wind waves: Their structures, distributions, and energy balances. Ph.dD. thesis, Scripps Institution of Oceanography, University of California, San Diego, 1993,124-172
[28] 陈国华, 佘敬曾. 海水表面张力的研究: 海水表面张力同温度和实用盐度之间的经验关系. 海洋与湖沼, 1994, 25(3): 3.6-311
[29] 胡昌华, 张军波等. 基于MATLAB的系统分析与设计—小波分析. 西安电子科技大学出版社, 1999
[30] 胡广书. 数字信号处理―理论算法与实现. 清华大学出版社, 1997: 81-94
[31] 李彩凤, 施柏煊, 严惠等.色编码技术用于测量海面波浪坡度的研究. 浙江大学学报(工学版), 2004, 36(3): 335-338
[32] 马毅, 杨大力, 张杰. 基于小波变换的海洋SAR图像信息分层技术, 水动力学研究与进展, 1999, 14 (4): 168-174
[33] 宋平舰, 张杰. 二维经验模分解在海洋遥感图像信息分离中的应用. 高技术通讯, 2001, 11(9): 62-67
[34] 王岩峰, 丁永耀, 张福元等. 海面微结构光学测量装置的测量误差分析与波面斜率转换. 海洋科学进展, 2004, 22: 85-89
[35] 文圣常, 余宙文. 海浪理论与计算原理. 科学出版社, 1984
[36] 徐德伦, 于定勇. 随机海浪理论, 高等教育出版社, 2001, 24-52
[37] 张福元. 海面局部图像微尺度波谱计算方法. 硕士毕业论文, 内蒙古大学数学系, 2003, 19-25
[2] Bernd J, Klaus S.Riemer. Two-Dimensional wave number spectra of small-scale water surface waves. Journal of Geophysical Research, 1990, 95(C7): 11531-11546
[3] Charles Cox et al. Statistics of the sea surface derived from sun glitter. Journal of Marine Research, 1954,13: 198-227
[4] Charles, Cox. S. Measurement of slopes of high-frequency wind waves. J.Marine Res., 1958, 16(3): 199-225
[5] Corless R. M, Gonnet G.H, D.E. G. Hare. On the Lambert W Function. Advances in Computational Mathematics,1996,5:329-359
[6] Cos.S, Munk. W. Statistics of the sea surface derived from sun glitter. J.Mar.Res. 1954a, 13:198-227
[7] Cox.S, Munk.W. Measurements of the roughness of the sea surface from photographs of the sun’s glitter. J.Optical Soc.Amer.1954b, 44:838-850
[8] Cox.S, Palm et al. Laser probe for measuring 2-D wave slope spectra of ocean capillary waves. Applied Optics, 1977, 16(4): 1074-1081
[9] Cox.S. Measurement of slopes of high-frequency wind waves. J Marine Res, 1958, 16(3): 198-227
[10] Crapper,G.D. An exact solution for progressive capillary wavrs of arbitrary amplitude. J. Fluid Mech.1957,2(6):532-540
[11] Michael S, Longuet-Higgins. Parasitic capillary waves: a direct calculation. J.Fluid Mech.,1995,301:79-107
[12] Norden E. Huang et al. The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis, Proc. R. Soc. Lond. A , 1998, 454: 903-995
[13] Paul A. Hwang et al. A study of the wavenumber spectra of short water waves in the ocean, Journal of Physical Oceanography,1995, 26:1266-1283
[14] Phillips O M. The Dynamics of the Upper Ocean, Cambridge University Press, London, 1980
[15] Sun H Q, Qiu D H, Shen Y M et al. Wave measurement based on light refraction. Acta Oceanologica Sinica , 2004, 23 (2): 359-366
[16] Tetsu Hara et al. Frequency-wavenumber spectrum of wind-generated gravity-capillary waves. Joutnal of Geophisical Research, 1997, 102(C1):1061-1072
[17] Tetsu Hara et al. In situ measurements of capillary-gravity wave spectra using a scanning laser slope gauge and microwave radars. 1994, Joutnal of Geophisical Research, 99(C6): 12593-12602
[18] Wang Y F, Guan S, Huang W M, Zhang J, Ding YY. The short wave observation using the optical instrument for detecting microstructure of sea surface wave. SPIE Proceedings–Ocean Remote Sensing and Applications,2003, 4892:462-472
[19] Yoshiaki Toba. Local Balance in the Air-sea Boundary Processes I. On the Process of Wind Waves. Journal of the Oceanographical Society of Japan, 1972, 28: 109-121
[20] Yoshiaki Toba. Local Balance in the Air-sea Boundary Processes III. On the Spectrum of Wind Waves. Journal of the Oceanographical Society of Japan, 1973, 29: 209-220
[21] Zhang X & Charles S. Cox. Measuring the two-dimensional structure of a wavy water surface optically: A surface gradient detector, Experiments in Fluids ,1994, 17:225-237
[22] Zhang X, Charles S. Cox. Measuring the two-dimensional structure of a wavy water surface optically: a surface gradient detector. Experiments in Fluids, 1994, 17: 225-237
[23] Zhang X. Capillary-gravity and capillary waves generated in a wind wave tank: observations and theories. J Fluid Mech, 1995, 289: 51-82
[24] Zhang X. Observations on wave forms of capillary and gravity-capillary waves, Eur.J. Mech. B/Fluids, 1999, 374-388
[25] Zhang X. Wavenumber spectrum of short wind waves: an application of two-dimensional slepian windows to spectral estimation, Journal of Atmospheric and Oceanic Technology, 1994, 11:489-505
[26] Zhang X., J. Klinke, B. J?hne. A study of advection of short wind waves by long waves from surface slope images. The Fourth Air-Sea InterfaceSymposium, Sydney, Australia, 1999
[27] Zhang,X. A study of capillary and capillary-gravity wind waves: Their structures, distributions, and energy balances. Ph.dD. thesis, Scripps Institution of Oceanography, University of California, San Diego, 1993,124-172
[28] 陈国华, 佘敬曾. 海水表面张力的研究: 海水表面张力同温度和实用盐度之间的经验关系. 海洋与湖沼, 1994, 25(3): 3.6-311
[29] 胡昌华, 张军波等. 基于MATLAB的系统分析与设计—小波分析. 西安电子科技大学出版社, 1999
[30] 胡广书. 数字信号处理―理论算法与实现. 清华大学出版社, 1997: 81-94
[31] 李彩凤, 施柏煊, 严惠等.色编码技术用于测量海面波浪坡度的研究. 浙江大学学报(工学版), 2004, 36(3): 335-338
[32] 马毅, 杨大力, 张杰. 基于小波变换的海洋SAR图像信息分层技术, 水动力学研究与进展, 1999, 14 (4): 168-174
[33] 宋平舰, 张杰. 二维经验模分解在海洋遥感图像信息分离中的应用. 高技术通讯, 2001, 11(9): 62-67
[34] 王岩峰, 丁永耀, 张福元等. 海面微结构光学测量装置的测量误差分析与波面斜率转换. 海洋科学进展, 2004, 22: 85-89
[35] 文圣常, 余宙文. 海浪理论与计算原理. 科学出版社, 1984
[36] 徐德伦, 于定勇. 随机海浪理论, 高等教育出版社, 2001, 24-52
[37] 张福元. 海面局部图像微尺度波谱计算方法. 硕士毕业论文, 内蒙古大学数学系, 2003, 19-25
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