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Earth’s rotation, LOD (length of day), AAM (atmospheric angular momentum), seasonal oscillations
Abstract:
Variations of annual and semiannual oscillations in rotation parameters have been investigated on the basis
of length-of-day (LOD) as well as atmospheric-angular-momemtum (AAM) time series. These oscillations were deter-
mined using band-pass filters. In order to show the character of variations of seasonal oscillations, amplitudes, phases
and periods were computed by a least-squares adjustment with the method of modified harmonic analysis at quarterly
intervals. In addition, the seasonal imbalances in LOD and AAM budgets were determined and analysed in a similar way.
These discrepancies were corrected for tidally excited effects. The non-atmospheric oscillations without the annual tide
effect Sa and the semiannual tide effect Ssa have changeable amplitudes between 0.02 and 0.10 ms.
