Multifractal thermal characteristics of the western Philippine Sea upper layer

Abstract

Multifractal characteristics of the upper layer (above 140 m depth) thermal structure in the western Philippine Sea near Taiwan are analyzed using high-resolution, digital thermistor chain data. The power spectra at all the depths have multi-scale characteristics with the spectral exponent β in the range of (1, 2), which indicates nonstationary with stationary increments. The graph dimension varies from higher values such as 1.71 (in sublayer: 60 m), to lower values such as 1.59 (in second thermocline: 120 m). However, the information dimension varies slightly from 0.929 to 0.941. The multi-dimensional structure is stronger in nonstationarity (graph dimension) than in intermittency (information dimension). These results provide useful information for investigating turbulence structure in the upper layer of the western Philippine Sea.