用小波变换研究赤道西太平洋温度细结构

On temperature finestructures in the equatorial western Pacific Ocean with wavelet transform

使用小波变换分析了赤道西太平洋暖池区的CTD资料的温度序列，表明垂向温度细结构具有自相似特征，有可能使用分数维模型来描述．计算了温度序列的奇异性指数及其概率分布，发现此分布具有近似普适的形式．非零概率的负指数意味着温度剖面可能存在奇异点．对经小波变换后的序列的周期性统计表明周期△和尺度α遵从幂律标度△～αβ，β≈1．这提示着细结构背后可能存在简单的二分串级机制．小波变换的振幅反映了温度脉动的强弱．据此可以确定脉动能量的垂向分布和能谱密度，和传统方法的比较表明小波能谱较为光滑，有利于精确测定谱斜率．

──By using wavelet transform (WT), we analysed part of the CTD data collected from the equatorial western Pacific Ocean, the results show that the temperature finestructures has selfsimilarity and may be described with fractal. The singularity exponents of temperature series and their probability distributions are also calculated. The probability distribution functions (pdfs) have nearly a universal form. The nonzero probability at negative exponents implies the possible existence of singular points in the temperature profiles. When computing the average period of the WT, we found that the mean period A of WT of the temperature series has a power dependence on the transform scale a, that is, △～aβ, with β≈1. This suggests that a simple dichomotous cascading mechanism may govern the finestructure dynamics. In addtion, since the amplitude to of the wavelet transform is related with the strength of temperature fluctuations, the vertical distribution of fluctuation energy can be calculated with wavelet transform. Compared to the FFT spectrum, the WT spectrum is more smooth and is capable of giving more accurate spectral slope.