Modelling and prediction of the FCN Maciej Kalarus 1 Brian Luzum 2 Sébastien Lambert 2 Wiesław Kosek 1 Maciej Kalarus 1 Brian Luzum 2 Sébastien Lambert 2 Wiesław Kosek 1 Journées 2005 Systèmes de Référence Spatio-Temporels Warsaw, September Space Research Centre, Polish Academy of Sciences 2 United States Naval Observatory
Input data Modelling and prediction of the FCN Atmospheric Angular Momentum NCEP/NCAR ( August 2005) four-times daily data reanalyses Nutation residuals IERS C04( August 2005) daily data IAU 2000 Gravity field C 20 Cox & Chao( December 2002) variable 2/9
Wavelet analysis Complex Morlet Wavelet f b – bandwidth parameter f c – wavelet centre frequency T - dilation parameter (scale) t i - translation parameter (space) Complex Wavelet Transform Coefficients Modelling and prediction of the FCN 3/9
Wavelet analysis of the nutation residuals amplitude high low Wavelet transform modulus Period [days] Gradient of the phase Period [days] ++ -- 0 ++ -- 0 + _ 0 Modelling and prediction of the FCN 4/9
FCN - model Level of the residuals epoch A n [ as] sin cos 01-Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan T FCN =442.3days dX MHB2000 dY MHB2000 Modelling and prediction of the FCN 5/9
Prediction of the FCN model Modelling and prediction of the FCN 6/9 dX dY Distribution of the prediction errors for 180 days in the future RMS prediction error error computed in 1986 – 2004
Possible excitation of the FCN FCN period Gravity field C 20 nino4 El Niño event 1997/98 Modelling and prediction of the FCN 7/9 AAM annual oscillation AAM annual oscillation FCN annual AAM p Wavelet transform modulus Wavelet transform modulus
Conclusions Characteristic of the FCN model - variable amplitude and period (phase) - apparent relationship to geophysical phenomena - mean prediction error as for 180 days in the future - earthquakes (T. Shirai, T. Fukushima) - anomalous fluctuations in the core (C. M. Cox, B. F. Chao) Other possible sources of excitation - subpolar glacial melting (J. O. Dickey, S. L. Marcus, O. de Viron, I. Fukumori) Modelling and prediction of the FCN 8/9 Possible excitation of the FCN Impulse excitation - global mass redistribution - perturbations of the annual atmospheric and oceanic circulation - land hydrology
Thank you for your attention Acknowledgements: This research has been partially supported by the Descartes-Nutation project.
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