The Sea Surface Micro-structure Of Image Data Processing Algorithms And Systems Integration

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".