Bispectra of spike-array type time series and their application to the analysis of oceanic microstructures |
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Authors: | Yutaka Nagata |
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Institution: | (1) Geophysical Institute, University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, 113 Tokyo, Japan |
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Abstract: | Bispectral analysis is applied to records of the vertical profile of the vertical temperature gradient in the oceanic thermocline in the San Diego Trough. The bispectra exhibit three notable features; (1) bispectral peaks at the points (0.2 m–1, 0.2 m–1) and (0.2 m–1, 0.1 m–1), (2) bispectral ridges along the lines (
1=
0,
2=
0 and
1+
2=
0 corresponding to peak wavenumbers
0 in power spectra, and (3) array of bispectral peaks of interval of 0.2 m–1 The results are compared with the bispectra of several modeled time series of spike-array type. The periodicity of 5 m found in the records seems to have two meanings: spacing of predominant spikes and wavelength of predominant sinusoidal wave. If this indicates the existence of internal waves having a vertical wavelength the same as the scale of homogeneous layers, it would suggest the possible importance of internal waves in the formation and maintenance mechanisms of oceanic microstructure. |
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