Mathematics – Logic
Scientific paper
Jul 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006acasn..47..301l&link_type=abstract
Acta Astronomica Sinica, vol. 47, no. 3, p. 301-309
Mathematics
Logic
2
Variation Of Earth Rotation, Chandler Wobble, Atmospheric Excitation, Wind Excitation
Scientific paper
This study estimates the mean energies of the observed Chandler wobble(CW) excitation, various wind excitations, the mean coherent coefficients and phases between them by using methods of the FFT and multitaper coherent analysis and data of the space2003 polar motion series and various wind angular momenta for 1980---1993 and 1980---2003, respectively. The various wind momenta were calculated recently by integral from the real surface or mean sea level (1000hPa) to the model height (100hPa or 10hPa) by using the modified or unmodified reanalysis data of the National Center for Environmental Prediction (NCEP) by Japan Meteorological Agency (JMA).The results show that the mean excitation energies of the global tropospheric wind (integral from the real surface to 100hPa) and tropospheric + stratospheric wind (integral from the real surface to 10hPa)can explain about 68% and 72% (58% and 51%) of the observed CW excitation for 1980---1993 (1980---2003) respectively, with dominant contributions from the tropospheric winds. And the squared coherence between these wind excitations and the observed CW excitation are 0.49 and 0.32 (0.50 and 0.39) respectively, with approximate zero coherent phases. It reveals the important role of the wind contribution in CW excitation. This study also shows the different effects of various wind angular momenta calculated by integral from different layers and model heights, and by using the modified or unmodified reanalysis data of the NCEP on the estimates of the CW excitation. Detailed results of the mean energies, squared coherence and coherent phases of the various wind excitations in Chandler band (0.8---0.9cpy) are listed in table 1. As an example, the power spectral density (a) of the various wind excitations and observed CW excitation, squared coherence (b) and coherent phases (c) are shown in Fig. 1 for 1980---2003. Also shown in Fig. 2 are the temporal variations of the mean energies, squared coherence and coherent phases in Chandler band which are calculated by using 12-year sliding window with a 3-month step forward.
Liao De-Chun
Liao X.-H.
Zhou Yan-Hong
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