Spectrum-Representation, Adaptive Recognition Of Spring Layer And MODIS Application In Study Of Internal Waves

This paper put forward a method, which expresses the spring layer through the spectrum of the whole water layer’s profile. This method make the process of vertical change and the character become prominent comprehensively, systemically, completely, accurately,which uses the zero line and the distribution of gradient of the marine elements’ vertical change. The turning character of the spectrum peak’s root is taken by using the most value of curvature area and adaptive detecting of wavelet transforms respectively, at the same time, the demarcation between upper and lower water column is determined. Thus we from a method named ’Five points and three factors’, which can respective the features of spring layer comprehensively. Five characteristic points namely the upper bound of spring layer and strong spring layer, the most value of spring layer, the lower bound of spring layer and strong spring layer. The three strength factors of spring layer are greatest intensity of spring layer, average intensity of strong spring layer and spring layer. Based on this, we build a systemic method to definite, express, determine and reorganize spring layer.Describe the spring layer of the South China Sea by using the method on reanalysis data of temperature and salinity profiles of EN4, and obtain the distribution of internal wave and its parameters resulted from reversion of the South China Sea based on the MODIS optical remote sensing data. The result shows that, internal wave of the South China Sea is mainly distributed over the west of Bashi Channel to areas such as Dongsha, Liuhua area,the pearl river estuary,the water depth of 200 meters and the shelf break area at depths less than 200 meters.The emergence of internal waves in the South China shows significant seasonal variations, the frequencies of internal waves surge is highest in summer, spring and autumn is less and the least in winter. It is obviously related with the strength of sea water stratification, the spring layer is strongest in summer in the South China Sea; spring and autumn is weaker, and the weakest in winter.The amplitude of the internal wave in the northern South China Sea is spread from meters to hundreds meters, and the wavelength of it is spread from hundreds meters. There are internal waves with extremely large amplitude in areas such as Liuhua, Dongsha, Baodao, Fanyu and so on. During the internal wave in the northern South China Sea spreading from the Luzon strait to the west, its speed and wavelength is decreasing gradually.