Wavelet-Analysen ozeanischer Drehimpulszeitreihen

Abstract

This report presents the results of a wavelet analysis of Ocean Angular Momentum (OAM) time series, that were generated by the OMCT-Model (Ocean Model for Circulation and Tides). The findings from this analysis were then compared with the same time series that had been projected in the fre-quency domain, using the Fast Fourier Transformation. The oscillations we studied are located in the period window between 14 days to 20 years. From the wavelet transformation, we find that the strictly periodic oscillations (e.g. fortnightly, semiannual, annual) of the tide-driven OAM are modulated by the moon cycle (18.6 years). In addition to the dominant annual oscillation in the mass term of the atmospheric-driven part, we find also non-strictly periodic signals with periods up to one year. The cycle durations of the powerful quasiperiodic oscillations are between 4 and 12 years. A quasiperiodic oscillation in the axial mass term of the atmospheric-driven part can also been correlated with the eleven-years solar cycle. Furthermore, the atmospheric-driven part of the OAM time series shows some aperiodic oscillation be-tween one and three years.