经验模态与小波分解在光学遥感内波参数提取中的应用

Application of empirical mode decomposition and wavelet in retrieving internal wave parameters from optical remote sensing

内波遥感参数提取是利用遥感影像研究海洋内波的重要手段,通过提取内波的基本参数可以对海洋内波的生成与传播机制进行进一步的研究。提出了利用经验模态分解、小波分解与高阶多项式拟合从光学影像中提取内波半波宽度的方法。经验模态分解与小波分解对内波剖面数据进行尺度分解,根据归一化方差最大来提取内波分量;多项式拟合基于内波剖面的亮暗条纹变化完全由内波调制的假设,对数据进行拟合,并根据一阶导数来提取半波宽度。用南海北部东沙岛附近2004年7月10日的中-巴资源卫星(China-Brazil Earth Resources Satellite,CBERS)影像对方法进行了验证。结果表明,3种方法能较好地提取所需参数,获取的内波半波宽度具有较好的一致性;上述方法在处理非平稳及非线性遥感数据上,具有非常明显的优势。基于一维非线性内波理论,通过提取的内波半波宽度,辅以水深和混合层深度数据,反演了内波的振幅。

Retrieving internal wave parameters from remote sensing data plays an important role in internal wave research.The generation and propagation mechanisms of such waves can be studied using the parameters extracted from remote sensing data.The authors use empirical mode decomposition,wavelet decomposition and high-order polynomial fitting in extracting internal waves’（IWs） half-wave width from optical remote sensing images.With the method of Empirical mode decomposition and wavelet decomposition the remote sensing data is decomposed and the signal of IWs is extracted by the normalized variance of IWs.Polynomial fitting is based on the assumptions that bright and dark stripes completely change within the wave modulation and that the first derivative the half-wave width can be extracted.The three methods have been verified by the image of China-Brazil Earth Resources Satellite（CBERS）,which was imaging the northern South China Sea near Dongsha Atoll on July 10th,2004.Results show that the three methods can effectively extract the needed parameters with all the results of half-wave width being in good agreement with each other.The above methods have obvious advantages in dealing with non-stationary and nonlinear remote sensing data.Using the extracted half-wave width data and other related data（water depth and mixed layer depth）,the authors retrieve IWs’ amplitude base on the nonlinear internal wave theory.